Perhaps not all booms are bad:
About four minutes after SpaceX's gargantuan rocket lifted from its Texas launch pad, it burst into a fireball over the Gulf of Mexico, never reaching space.
Though SpaceX hasn't shared many details yet about what happened during Starship's maiden voyage, one fact is known: It was intentionally ordered to explode.
Rockets are destroyed in the air when people's lives could be even remotely at risk of falling debris. In the days since the uncrewed test, no injuries or major property damage appear to have been reported.
When the rocket launched at 9:33 a.m. ET April 20, 2023, some of the rocket's 33 booster engines had either burned out or failed to light from the start. As Starship ascended, cameras caught views of the flames underneath it, appearing to show some of the engines had cut out.
In a statement released after the incident, SpaceX said Starship climbed to about 26 miles over the ocean before beginning to lose altitude and tumble. Then, self-destruct commands were sent to the booster and ship, which hadn't separated as planned, the company said.
What ultimately initiated that disintegration isn't completely clear, Dan Dumbacher, executive director of the American Institute of Aeronautics and Astronautics, told Mashable.
"Now it's a pure race as to whether the aerodynamic pressure breaks the vehicle up or the flight termination system does," he said, "but it really doesn't matter because the end result is the same."
As Starship ascended, cameras caught views of the array of flames underneath it, appearing to show some of the engines were out.
"There's a lot of risk associated with this first launch, so I would not say that it is likely to be successful," [Elon Musk] said during a video conference with a National Academies panel in 2021. "But I think we will make a lot of progress."
Despite Starship never having reached space, industry experts largely regarded the launch as a partial success because the rocket managed to clear the launch tower and traveled higher than any Starship prototype had before.
Meanwhile, the general public seemed unsure of how to think of the whole thing: After all, usually, when something big and expensive goes boom, it's considered bad. But SpaceX has always approached rocketry differently from NASA, working a little messier and faster to achieve its goals.
In terms of the explosive ending, Dumbacher said spaceport safety officers are required to terminate a flight if a rocket meanders into an area where the risk of debris hitting someone on the ground could exceed a probability of one in 30 million. "People ought to be looking at this as good — the flight termination system, if it was needed, actually worked," he said.
(Score: 5, Interesting) by Barenflimski on Monday April 24, @06:26PM (5 children)
What is interesting is that while it worked, it didn't work as planned.
The main idea is to blow the entire thing up so that smaller pieces hit the ground.
What really happened is they initiated the explosive devices. They detonated. They put two holes in the side of the tank. Instead of blowing the entire thing up, the fuel leaked out. Once the tanks were depressurized, and out of nitrogen to keep the tanks at full pressurization, then it came apart on its own.
It took ~53 seconds between initiation of the system until it fell apart.
In case you want to hear someone else explain it -> https://www.youtube.com/shorts/cqbIwZMvbqw [youtube.com]
(Score: 3, Interesting) by ElizabethGreene on Monday April 24, @08:30PM (4 children)
I am not an expert on this topic. Is the flight termination system considered critical ground safety equipment? If so, would this failure require SpaceX to explain and remediate it before they get another launch permit from the FAA?
(Score: 4, Informative) by Barenflimski on Monday April 24, @09:03PM
I'm not sure if its considered "critical ground safety equipment".
It is required for any launch. Every system that launches, needs this system on it, and it must function correctly.
Due to this, the system will need to be redesigned. In this case, what will likely happen is they'll add either a few more of these firecrackers devices to the side of the rocket OR they'll add a increase the size of the firecracker to the existing devices.
(Score: 2) by RS3 on Monday April 24, @11:16PM (1 child)
Right after the launch failure an article said the FAA had revoked SpaceX's launch license. This isn't that article, but mentions it:
https://www.houstonpress.com/news/spacex-launches-throw-debris-across-a-nearby-beach-15534625 [houstonpress.com]
(Score: 2) by takyon on Tuesday April 25, @12:16AM
This is the license that gives them up to 5 launches a year from Boca Chica, even though technically the FAA has to approve each launch individually in the end?
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 2) by JoeMerchant on Tuesday April 25, @01:16AM
In theory, yes. In practice: I believe permission to launch again is more a question of how the politics wants to perceive the shades of grey...
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(Score: 5, Interesting) by istartedi on Monday April 24, @06:38PM (57 children)
That the rocket was intentionally destroyed when it lost control isn't news to anybody with much knowledge about rockets. I'm given to understand that traditionally the decision to do this is made by the RSO (Range Safety Officer) which seems like something that comes out of the military. I don't know if SpaceX carried this role forward (no pun intended) but it seems likely.
What I didn't know about this rocket in particular is that apparently it was *suppose* to tumble once, fling the booster off, then reorient itself and ignite the next stage. The source said this was to save the weight of the customary stage separation hardware; but given the scale of all this I'm wondering why you'd chose to do such a complex separation maneuver. How much weight is really saved? Enough I guess, otherwise it seems like they wouldn't have tried this. We thought landing back at the pad was crazy, but now we realize it's the best kind of crazy. Maybe this is too.
Appended to the end of comments you post. Max: 120 chars.
(Score: 4, Disagree) by JoeMerchant on Monday April 24, @06:51PM (56 children)
What I found interesting was the massive destruction of the launch pad, and that "analysis of the static firing test data indicated this shouldn't be a problem."
Learn by doing: yes. Saying you analyzed the test data, but missed the actual outcome by such a wide margin? Sounds like you don't know how to analyze your test data.
>it was *suppose* to tumble once, fling the booster off, then reorient itself and ignite the next stage.
This smacks of "because we can" showboating. It will be cool when they get it right, and hopefully they do eventually get it right, but I seriously doubt that mid-ascent acrobatics are really lower cost / lower risk overall than just including stage separation hardware. Would be interested to know what the design limits are for negative Gs during the tumble maneuver, and what the actual experience is like for the passengers.
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(Score: 4, Interesting) by Immerman on Monday April 24, @08:37PM (8 children)
I don't know - so long as the clamps actually let go (an unavoidable concern for ANY stage separation), there's not much that can go wrong with a centripetal separation in near vacuum. And it eliminates all the other things that might go wrong - a part that doesn't exist, can't possibly fail.
Now, having both stages recover from the resulting tumble afterwards... THAT might be challenging. But my understanding is that SpaceX actually has a lot of practice with that from their Starlink launches.
As for the G forces -
I counted ~3.5 revolutions (let's be pessimistic and call it 4) in 50 seconds. Assuming it's revolving around the interstage region (it should be biased even closer to the Starship, since SuperHeavy is now running on fumes, but we're being pessimistic), and passengers are way up in the nose, even in front of the header tanks, we're talking 12 seconds per revolution at a distance of ~120m. Linear acceleration = w^2 * r, so (2pi/12s)^2*120m = 5.2m/s
So, even rounding all assumptions towards maximum pessimism, we're still only talking ~0.5g. About what you'd experience when slamming on the brakes in a car.
(Score: 2) by JoeMerchant on Monday April 24, @11:01PM (7 children)
Just to argue the other side, 0.5g isn't a lot, but in a relatively small circle at otherwise 0g might be a bit of extra nausea induction right when it already hits a lot of highly trained astronauts with tons of atmospheric flight experience.
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(Score: 2) by Immerman on Tuesday April 25, @02:45AM (6 children)
Sure, I'd bet some nausea is present - but you experienced much higher acceleration around a much smaller radius when you got thrown off the merry-go-round as a kid (assuming you're old enough to have enjoyed playground equipment that offered a non-zero chance of injury)
And it's probably a safe bet that separation occurs within less than one revolution as well. While ignition probably occurs almost immediately afterwards, with stabilization not far behind.
Not the most fun experience ever - but nothing about a rocket launch is. A major design limitation is what our fleshy meat-sacks can reliably survive, comfort isn't even on the negotiating table.
(Score: 2) by JoeMerchant on Tuesday April 25, @03:02PM (5 children)
>you experienced much higher acceleration around a much smaller radius when you got thrown off the merry-go-round as a kid
I did all that stuff as a kid. When I turned about 25 it went from fun to seriously headache inducing. By 35 it's just plain bad for me so I don't do it anymore.
Gs are one thing, Gs in tight radius rotations (like carnival rides) are something else entirely.
>A major design limitation is what our fleshy meat-sacks can reliably survive, comfort isn't even on the negotiating table.
I'm sure the flight discomfort containers (barf bags) are available in easy reach already, I'm just not sure that you'd call a maneuver that fills up twice as many of them as the previous protocol an overall improvement.
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(Score: 2) by Immerman on Tuesday April 25, @04:02PM (4 children)
Ah, good times. I was sorry to see them go. Seems like we've been removing every way for kids to hurt themselves, and then getting surprised when they grow into young adults with no sense of risk management.
"Tight radius" is relative - The Starship stack is considerably taller than the huge ferris wheel in Las Vegas - until recently the tallest in the world. Much larger, and much lower accelerations, than the merry go rounds of our youth. I'm sure astronauts can handle a handful of seconds of it - they're subjected to much worse in training.
(Score: 2) by JoeMerchant on Tuesday April 25, @05:55PM (3 children)
Are you talking about the high roller thing? That's not so much a ferris wheel as an elevator car that takes 30 minutes I think for a revolution - we rode it once, the major feature was the wet bar in the car...
I'm sure everyone will come through intact, but if you had side-by-side choices of which vehicle to ride to orbit, there might be people where that maneuver would establish the preference...
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(Score: 2) by Immerman on Tuesday April 25, @06:40PM
Looks like: https://en.wikipedia.org/wiki/Ferris_wheel [wikipedia.org]
I guess the name doesn't make a distinction between open chairs and closed cars, and cars are pretty common among the largest ones.
(Score: 2) by Immerman on Tuesday April 25, @06:52PM (1 child)
Oh, and yeah, if there was a competitive alternative I could see it making a difference - though as I recall, 100m (radius? diameter?) is generally accepted as the lower limit to provide 1g of artificial gravity *without* inducing nausea, so they *should* be well in the clear. Especially considering they'll be spinning before the engine cuts off, so cabin "gravity" should go directly from pushing them into their chair to pulling them out of it, to being pushed back into it as the engines fire up and correct the tumbling, with only momentary zero-g periods during the transition. Might even be less nauseating than a more traditional separation.
Could still be a bit "carnival ride" for many people's tastes... and they'll be free to pay the competition 100x as much for the trip if they're so inclined. At least until real competition finally catches up - RocketLab might have a chance of doing so eventually...
(Score: 2) by JoeMerchant on Tuesday April 25, @07:30PM
NASA astronauts ride for free...
I suspect the worst part of the rotational separation would be if you had a nice view of the moon and the stars in a steady-ish location until the maneuver, then everything starts to spin. Closing your eyes (if your duties allow) should help. And, it's gonna look super cool on the TV animations, so there's that...
When I was 16 I rode the teacups in Disney World just after eating a batch of cold greasy french fries, then getting a frozen fruit pop in the line for the teacups, the line moved really fast so I had to eat the frozen fruit pop fast. Then we spun, hard, and at one point I laid over sideways - bad move, had ridden the teacups about an hour earlier without laying over, had no problems from that with the world spinning on my Z axis (head to toe), but with the nasty food gulped down, then laying over, then standing up and walking out of the cups area, the world was still spinning for me in kind of a "rotating upwards" on the X axis (arm to arm) direction - so those fries and fruit rotated upwards into the planter just outside the exit... Teacups do spin much harder than the separation maneuver, in a much tighter circle, but it was really that semi-visual sensation of the world spinning up on me that triggered the "release" reflex. And, even with training, some people are going to have some fear of death butterflies working during a launch so they're already "primed" for some reflex reactions.
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(Score: 5, Interesting) by RS3 on Monday April 24, @08:49PM (46 children)
Sorry I don't have a link (yet)- I've been sick for a few days. Much too familiar story I read somewhere said that someone, an engineer perhaps, tried to warn SpaceX management that the launch pad was horribly deficient and would be destroyed, but he was rebuffed. Same story said the several non-firing engines were damaged by chunks of concrete that blew up and around. There may have been more damages, including sensors, controls (motors, solenoids, valves, actuators, etc.), and controllers, so at that point it's pretty far beyond design tolerances. Knowing that, I'm pleasantly surprised at how well it did fly.
A good friend's Ford F150 went into "limp home mode" on him one day. It did limp, 10-15 MPH. He figured out that most of the sensors weren't working. It turned out there were many pinholes in the wiring under the hood, and the wires had turned into green powder internally (copper oxide, which doesn't conduct electric current very well). He buzzed out and patched everything. I was very impressed that the ECU could tolerate that many sensor signal losses and still run at all.
(Score: 3, Informative) by JoeMerchant on Monday April 24, @11:08PM (45 children)
I read the same part about flying debris taking out several engines. It does say good things about their compartmentalization of function that the remaining engines did so well.
My article went into ramifications for moon and Mars missions needing launch infrastructure (good pads) although on the moon they might achieve liftoff with high mounted thrusters until clear of debris risk.
Didn't hear about the ignored warning until here, thanks for that. It's an organizational maturity thing, one reason I wasn't even sad that I can't afford a seat on Bezos or Branson's sub-orbit mobiles.
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(Score: 2) by RS3 on Monday April 24, @11:39PM (44 children)
Like so many, as a kid I seriously dreamed of spaceflight, including being the first man on Mars. Over the years I've not only lost that interest, but increasingly I'm so very disappointed in the shortsightedness, corner-cutting, you know, all the things that are antithetical to the best and highest quality attainable, especially for things like nuclear power, planes, rockets, bridges, etc.
I wish I could find that aforementioned article. It mentioned them using a flat concrete pad, rather than blast deflection that NASA used (AFAIK) in most launches, esp. Saturn V.
Also they corner-cut and did not use a water spray system. I'd love to know how much they actually tested, calculated, computer simulated, etc., versus wet a finger and held it up to the wind. Sorry for this cynicism, but I see too much of the "oh, that's so old, we're so much better now" attitude, rather than learning from the past, what we've learned, and build on it and augment it.
They're talking about a big thick water-cooled steel plate under the launch, but they're not sure if it will melt. Let's see, what could possibly go wrong, molten / vaporized steel being blown at super-sonic speeds...
As a lifelong experimenter myself I sort of admire their willingness to try these experiments, but again, it just seems dumb to completely delete the water spray system when you're launching the biggest rocket ever.
High-mounted thrusters sounds interesting. I still vote for spring-loaded launcher legs. :) (I'm mostly kidding, but maybe?)
(Score: 2) by JoeMerchant on Tuesday April 25, @12:35AM (3 children)
>how much they actually tested, calculated, computer simulated, etc., versus wet a finger and held it up to the wind
I wouldn't be surprised if it was a deliberate risk taken on the chance that they could prove the existing players wrong about needing a sophisticated launch pad system.
>spring-loaded launcher legs
If the engines can build thrust fast enough you could build a tower out of balsa wood or something similarly disposable to hold the vehicle high off the ground, but the ignominy of a slow start and subsequent fall to the ground would last forever... Problem with springs is again: engine failure to reach sufficient power for control before approaching the surface again.
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(Score: 2) by Immerman on Tuesday April 25, @03:14AM (2 children)
I think it's more than just proving the existing players wrong, though testing conventional wisdom from a long-stagnated field is probably a good idea. I mean, the launch tower and pad are already more expensive than the whole rocket.
Like you alluded above, I think a big part was likely testing for Mars, the moon, etc. If they need fancy flame trenches and water deluge systems for a safe launch... that's going to be a problem.
Granted, SuperHeavy is a lot more powerful than Starship... but Earthside construction is a lot easier and more predictable than off planet.
(Score: 2) by mhajicek on Tuesday April 25, @07:41AM (1 child)
The Superheavy booster is never intended to launch from Mars or the moon, just the Starship with it's three to six engines. The Lunar Starship design includes engines positioned like gills on a fish for final landing, which could also be used for initial liftoff.
The spacelike surfaces of time foliations can have a cusp at the surface of discontinuity. - P. Hajicek
(Score: 2) by Immerman on Tuesday April 25, @02:52PM
I've heard lots of conflicting things about the lunar Starship plans. In fact, I think the closest thing to official confirmation that the rendered "gills" are actually thrusters, was when Musk talked about maybe not needing the hot-gas thrusters to land on the Moon after all.
I swear, nobody reads beyond the first sentence. Yes, the Starship has a lot fewer engines - but building a remotely comparable launch pad on Mars is also not a realistic option in the near term. The engines will also ignite practically on the ground, without the benefit of a launch platform holding the ship 15m(?) off the ground.
And thanks to the higher gravity, the much weaker hot-gas "gill engines" probably can't provide enough thrust to get off the ground on Mars. If something like them turns out to be necessary it will likely need to be liquid-fueled engines, creating a huge engineering problem since they can't be gravity/thrust-fed, and good luck pumping that much fuel against the acceleration of launch.
(Score: 2) by JoeMerchant on Tuesday April 25, @12:45AM (12 children)
Random thought: we just poured a concrete pad with 3000 psi rated concrete. Some skyscrapers use concrete rated up to 12,000 psi (compressive strength)
I wonder: A) what the psi generated by BFR is at launch, and B) if they even tried to make a strong pad with highly rated engineered concrete, or if they just ordered up 24" of whatever the local RediMix plant could supply?
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(Score: 2) by JoeMerchant on Tuesday April 25, @01:11AM (11 children)
17 million pounds of thrust, over a 30 foot diameter base, 700 square feet, 100,000 square inches, so 170psi.
Why sheeoot (in the voice of Slim Pickens) I don't h reckon 5000 psi concrete cured for a month or two aught to handle that just fine.
Next crazy redneck engineering idea would be inverted pyramidal wells in the concrete filled with crushed ice, for the double phase change to avoid it all boiling away before the rocket clears the tower. Maybe hexagonal shaped instead of square, 10 square feet each, 6 feet deep in a pattern of 105. Say 3000 cubic feet of ice in total, about 10,000kg @ 3,000,000 J per kg, that is 30 Gigajoules absorbed before the pad starts exceeding 100C. Now, how many Gigajoules of heat per second comes from 17 million pounds of thrust?
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(Score: 3, Informative) by RS3 on Tuesday April 25, @02:09AM (5 children)
We're making a true rocket scientist out of you. :)
I'd have to look at many factors. Rocket blast isn't laminar, but I don't know what the peak burst PSI are, but it might be many times that average.
Also, the fire isn't spread out, it's hopefully quite focused by the nozzle. It's counterintuitive, but the bell shaped nozzle actually hyper-focuses the blast. I haven't looked at video yet, but I'd bet you could see the spots under each engine- for a hot second.
One from personal experience: I don't do much stone / masonry, but there's a technique of using a torch, like Bernzomatic, oxy-acetylene, etc., on stone surface and most types of stone will burst out explosively in thin layers. IE, it's a way to sculpt stone, and I know for a fact that concrete will do this too. Fairly simple to visualize- that top layer expands really fast and has nowhere to go but pop. It'll pop before the heat gets down to deeper layers. The hotter the flame, the more you get the result. Safety glasses and clothing are necessary.
Not concrete expert, but generally they mix in fibers to strengthen the concrete. Cure rate is critical to it being strong (fast cure is not good). Many think of concrete as "drying", but it's a chemical reaction and if it dries too fast, the reaction stops. Correctly done, concrete gets quite warm as it cures, so good masons often cover it with something to prevent it drying before it's cured.
(Score: 2) by JoeMerchant on Tuesday April 25, @10:04AM (4 children)
Concrete is porous, water gets inside and if you superheat that water it will expand explosively causing spalling, like you describe for rock. I used to do that on my sidewalk trying to burn out weeds with a propane torch.
The Slim Pickens voice is meant to convey a gross oversimplification ignoring many factors, like sudden heating, non-uniform loading, vibration, oscillation, etc.
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(Score: 2) by RS3 on Tuesday April 25, @04:13PM (3 children)
Yeah, I learnt the hard way once. I was probably soldering copper pipe fittings on some concrete, so face fairly close to the action. Hit the concrete a bit, thought "no worries" and it exploded at me. Quite scary, and glad it didn't hit an eye. But again, I've seen stone masons use torches to sculpt stones. Water will flash to steam for sure, but again, that sudden expansion of the top layer causes the rapid outward push even with minimal water (non-porous rock will do it too).
I got the "Slim Pickens" thing- I know a few of them types, sometimes I might even be one! In fact I often adopt that voice, esp. with friends and some co-workers (and often talking to myself!) "What could possibly go wrong?" and "hold my beer" and "watch this!". Gotta have some fun in life, right?
(Score: 2) by JoeMerchant on Tuesday April 25, @06:05PM (2 children)
>Gotta have some fun in life, right?
Absolutely, although not at my job of the last 10 years...
The job before this one (more or less) was with a "move fast and break things" company of young kids making mini-UAVs. They often said "if you don't lose a plane once in a while, you're not taking enough risks." Now, I asked them, several times, are you sure you want to fly the prototype autopilot, on basically untested software, without the tracker beacon? (We only had two beacons, and the manual control human pilots always wanted them...) and sure they said, we don't need it. So, after about 5 or so flights like that, we went out one day with new comms software - and comms were kinda sluggish and flaky for the whole 45 minutes of the flight, but commands and telemetry were still getting through... and the prototype altimeter had drifted enough during the flight that I knew: if we let it run the automatic landing cycle it's going to stuff itself in the trees, guaranteed. So, I asked to go to manual control on final approach, which they did, and then all comms stopped going through and we watched the plane disappear over the other tree-line out into 7000 acres of state park swamp... Many valiant efforts to find the vehicle were made, but the approximate location where we think it ran out of battery was over a feature called "Itchy bottom pond." Biggest concern was that the plane continued on into the city (where it was headed) and crashed on a school or something else equally headline grabbing. Now, these UAVs were about 18" long, weighed about 3.5 lbs... but that doesn't change the "LOCAL UAV MANUFACTURER LOSES CONTROL OF THEIR PLANE AND IT CRASHES INTO AN ELEMENTARY SCHOOL PLAYGROUND" headline. As far as we know, to this day it has not been found. They quit flying without radio trackers after that.
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(Score: 2) by RS3 on Tuesday April 25, @07:09PM (1 child)
Yeah, I'm a bit more conventional. I'm okay with some experimentation, but I like a solid base of provens. Sounds like aforementioned young'ens were willing to experiment with too many unknowns. I like analogies with construction: it's like playing with roofing materials when you don't have a solid foundation and footing and the building starts slumping.
I don't know much about UAVs, but I would want a two-way "heartbeat" signal, and autoland if vehicle loses signal. Maybe that's the way it's done? You'd hope those designs and systems are well established. My impression of project / product development is faster and faster cycles- push / drive it and deal with problems later. I do better in the worlds where safety is more important.
I'm still doing occasional work for the nuclear power industry. I recently had to substitute a couple of transistors because the specified one is long out of production (but I can find some NOS if needed). Middle company inspects things down to the very tiny detail. Interestingly the substitute part is way better in every way. These shouldn't get radiation, but NRC still want to see that they'll withstand some. Original part was much more sensitive to / susceptible to radiation affecting performance, but I might have to recall them and put in NOS but worse old transistors. No way can we afford to have it all retested, but I did find some NASA and Ames labs data from the 1970s on various transistors and the effects of radiation on their operation.
You're dealing with some pretty complex interactions. As I'm writing I'm thinking of nightmare scenarios where one CPU is maybe doing too much and at some point nested interrupts and subroutines overflow a stack, or some external thing doesn't get serviced in time and boom. Testing is not likely to find the worst-case scenario unless it's absolutely comprehensive.
Not sure what RF frequencies you're using, but as I'm sure you know, the higher it is, the more interference you can get. Dual RF (diversity) is far more reliable, but I'm not sure if anyone is doing it. Pretty much all wireless microphone systems use it, but you can still get interference and dropouts. Most receivers have a setup mode where they'll "listen" to the RF environment and pick clear frequencies. The more mics, the crazier it gets with the sideband overlaps, heterodynes, etc. After all of that setup, when a room fills with people and their cellphones and Wifi and who knows what else, things can get bad fast.
Anyway, I would have thought you'd have to have tracker / beacon by FAA rules, but I don't work in that world so there's much I don't know.
(Score: 3, Informative) by JoeMerchant on Tuesday April 25, @08:09PM
>I would want a two-way "heartbeat" signal, and autoland if vehicle loses signal.
Well, we had that, and it was in place and would have worked, but... the altimeter inaccuracy was going to make that autoland into the tree tops. So, we didn't have an intermediate manual command mode on the prototype, we just had "regular" with the safeteis mode, and "full manual control" which would have accepted a single three byte command to "land right now, right where you are" but, it wasn't accepting any commands, so it just continued straight and level on present course. We had a video feed from the nose camera for a minute or so after it disappeared behind the trees.
After the fact, it occurred to me: the fault was in the ground station software, rebooting the ground station would likely have gotten comms back, but these are the things you think of after the 90 second window for successful heroic actions closes.
Also: comms were pretty notoriously flaky, so you wouldn't want to immediately land on a loss of comms for anything less than about a minute. But, yeah, if there were one of those safeties in manual control mode then we probably would have been able to find the plane, might have even had a video feed from it as it went down, and that video included GPS coordinates. But, again with the 90 second window thing, you'd be surprised how long it takes to copy GPS numbers off of wobbly 480p video, then input those into mapping software on a device you can use to practically navigate with.
> the substitute part is way better in every way.
We had a design from 1990 that used a six pack of inverters as a delay line (this from the chief engineer I replaced some years later, in 1991 I was a new hire), so... by 1994 or so, we couldn't get those old parts anymore and the new ones were so much faster that they didn't serve our purpose of delay anymore and broke the design. We did a last time buy in 1993 that filled all our needs, and my redesign in 1996 didn't rely on any delay lines.
There's no perfect answer for "cargo cult" requirements of "you always did it that way, the easiest thing for you is to continue doing it that way" but, "that way" is never 100% specified in all aspects, so sometimes an unspecified aspect will pop up and bite you as it changes over time. More often the "improved" parts will have unanticipated effects, often in very surprising places - surprises aren't great in nuclear reactors. And far more often than that: the newer part is just newer and better, but that's hard to regulate without trusting the engineers to be omniscient. I haven't met the omniscient engineer yet, and hope not to for many decades to come.
>You're dealing with some pretty complex interactions. As I'm writing I'm thinking of nightmare scenarios
Our nightmare scenario was that the ground station comms code was being written by a retrained air conditioning installation tech in his late 50s (like I am now...). Nice guy, conscientious, communicates well and politely, but the interrupt driven code on an embedded micro was just a little deeper water than he was really ready for to "get it right on the first try" and our 23 year old manager should never have gone flying without testing his new code some other way. Testing would have found the problem pretty quickly. In the field, we often had RF interference, and that's what this was presenting like. For 45 minutes we flew with the "return to base" safety on, but after 45 minutes of sluggish, but functioning, comms, it cut out altogether in the first 10 seconds after switching to manual control, which may have sunk the software with a higher volume of messages than auto mode. I made the call to switch to manual, and it was my mistake to be thinking the problem du jour was RF interference and not my office-mate's new code.
We had "diversity antennas" on orthogonal axes, but didn't really operate in two bands at once. Our modem was pretty slow data rate, something like 600 baud IIRC, and fuzzier still, I think it was in the 2.4GHz ISM band, you know: that ultra-crowded band with everybody's WiFi routers, bluetooth everything, and everything else on it too. It did have a little frequency hopping, they called it Spread Spectrum, but it was more like frequency sweeping.
The planes were so tiny, and this was 2009ish, I don't think there were any tracker or beacon rules in place at the time. They're not small enough that they fit the unregulated weight limits that came along later, but they're not too much bigger than that either. The main rules we were stuck with at the time was: military and police use only. Commercial use of UAVs in the US was all but impossible at the time, so we could fly "for fun" or development, but our only viable commercial customers were outside the US or military or some police uses. One of the earlier autopilot development prototype airframes was just a hobby "foamy" pusher body, much larger to support the larger 1st gen PCB. One day while we were flying that on a rented field we had a crop duster fly under our plane, we might have been at 150', he was closer to 90' - you could see his head turn to track our plane as he went by.
The thing that made all that (and quadcopters) possible were MEMS gyros. Automotive air bags drove MEMS accelerometer development hard and fast, but you can't really autopilot a small vehicle on accelerometer / magentometer data alone. Getting the miniature and affordable gyro channels for 9dof IMUs was the big change. When I joined the company they were buying an off the shelf autopilot for $5K per copy, and paying tens of thousands per year to develop any small modifications they wanted in the off the shelf software. They always wanted to make their own autopilot but weren't confident they could pull it off. A manager and I arranged a demo with the Flight Gear simulator software where I developed and ran autopilot software on a separate computer, taking only pose information from Flight Gear and only feeding back control inputs. That ran a waypoint course around San Francisco, and what clinched it was turning up the "weather effects" to crazy levels and seeing the control algorithms keep the plane on course through much worse weather than any sane person would attempt to fly in.
Україна досі не є частиною Росії Слава Україні🌻 https://news.stanford.edu/2023/02/17/will-russia-ukraine-war-end
(Score: 4, Informative) by Immerman on Tuesday April 25, @03:21AM (4 children)
They did use special high-strength concrete - they actually ripped everything out (twice?) after earlier static-fire tests and replaced it with stronger materials.
As I recall, the most destructive part is actually the sound. As you calculated, the actual average pressure is negligible compared to concrete's rated strength. But sound waves at those volumes hit like a stream of wrecking balls from a fire hose, and just tear shit apart.
The primary purpose of a water deluge system is not actually to cool things off, but instead to consume massive amounts of the energy being released to boil water rather than fueling those destructive sound waves.
(Score: 2) by legont on Tuesday April 25, @04:12AM (3 children)
That's why Russian pads are hemispherical structures that not only absorb, but reroute exhaust including sound sideways away from important equipment. Quite some math was used to calculate the exact shape.
"Wealth is the relentless enemy of understanding" - John Kenneth Galbraith.
(Score: 2) by RS3 on Tuesday April 25, @05:37AM
This was all I could find in a quick search, but you can see the Saturn V is suspended above a huge chute - the huge opening at the very bottom:
https://www.nasa.gov/sites/default/files/apollo_4_at_pad-full_0.jpg [nasa.gov]
I think that's a spare blast deflector in the right-hand background (big yellow thing).
I guess they didn't have enough time to cheapen the design. (/s)
(Score: 3, Interesting) by JoeMerchant on Tuesday April 25, @10:11AM
I still like hexagonal pits filled like snow cones from snow blowers, the steam expanding should be somewhat like a dome "pushing back" against the incoming blast. What could go wrong? ;-)
I also like a layer of battleship steel 6cm thick between the snow cones and the concrete underlayment.
Україна досі не є частиною Росії Слава Україні🌻 https://news.stanford.edu/2023/02/17/will-russia-ukraine-war-end
(Score: 2) by Immerman on Tuesday April 25, @04:25PM
Yeah, it seems like a flame diverter would be the minimum you'd want to try. Even if it's something half-assed they roll in before a launch and lock to the ground, you'd have *something* diverting the center of the flame column outwards, rather than it being confined by the flames of the outer engines.
(Score: 4, Informative) by Immerman on Tuesday April 25, @03:04AM (10 children)
Yeah, I've been rather disillusioned by the lack of a water deluge system as well - largely because one of its primary functions is to drastically reduce the amount of energy shed as sound waves (which do massive physical damage to concrete etc. at those volumes) by boiling water instead. Sound which, at the estimated volumes, would cause moderate to severe hearing loss to any-one/-thing without high-quality hearing protection anywhere within the pre-existing wildlife refuge they chose to put their launch facility in the middle of.
I'm all for well-run launch facilities in the middle of wildlife refuges, the synergy can work beautifully... but when your plan is to deafen all the inhabitants and turn the refuge into a buffet? That's no longer a beautiful synergy, it's just ruthless disrespect for everything but the bottom dollar.
As for reasons though - as I recall putting in the deluge system was estimated to delay launch by at least a year or two and impose a heft price tag. Because they can't just install it - they need to also build a massive water desalination plant to power it. Because using salt water is... very bad... for equipment, and the local municipal water supply can't handle the demand. Even the comparatively small SLS launch system consumes half a million gallons per launch.
(Score: 2) by RS3 on Tuesday April 25, @05:13AM (3 children)
I hadn't been paying much attention- thanks. I didn't know about the wildlife refuge, nor the water system cost and water needs. I wonder if they could use mostly salt water, then rinse everything with fresh at the end of the spray cycle?
An ex-coworker used to work in a steel mill. They would dump scrap steel into a large crucible (if that's what it's called) and push in 3 carbon rods 14" diameter, powered by 800 V at about 25,000 amps (IIRC). He said the sound was such that even with super amazing hearing protection, if you opened your mouth the sound energy would get in and destroy your hearing from the inside. IIRC you had to wear some kind of mouthguard. Best not to be anywhere near that operation.
A very brief websearch shows the carbon, graphite, etc., rods get much bigger than 14", and currents up to 90,000 amps. No human should be anywhere near something like that.
Anyway, all this makes me wonder if an orbiting assembly platform would make more sense, flying smaller rockets to supply it.
(Score: 3, Informative) by Immerman on Tuesday April 25, @03:07PM (2 children)
I don't think a rinse will cut it - I forget the details but I *think* the problem is that while salt is corrosive, salt superheated to rocket exhaust temperatures is *super* corrosive. Possibly even explosive? Like I said, I forget the details, but my takeaway was that saltwater is NOT an option, even for single-use rockets.
Orbital assembly would be great in the long term - but that's an entire industry we have to build from the (lack of) ground up. And something like Starship is necessary to get the equipment and materials up there cheaply enough to make it realistically feasible.
Honestly, I wouldn't be surprised if the Boca Chica facility remains just the factory and test facility it's currently licensed as, and the rockets/boosters just make separate low-power suborbital hops to the Cape Canaveral facility that's likely to be much more suitable for orbital launches.
It sounds like the long term plan is ocean-based launches anyway - though I shudder to think of the damage the sound could do to whales and other marine animals that rely on hearing as their primary sense.
(Score: 2) by RS3 on Tuesday April 25, @03:41PM (1 child)
Living_in_vacuum me, I hadn't heard of ocean-based launches. Far from expert, but wondering: re. ocean launches, is it possible to make underwater noise to drive away whales and other animals? And/or some kind of sonar system that would locate them and somehow keep them away, or delay a launch until they've gone far enough?
Hopefully they'd figure out some kind of underwater sound dampening system.
Also hopefully at the very least they (NASA, etc.) would work with marine biologists.
(Score: 2) by Immerman on Tuesday April 25, @05:52PM
Yeah, that was why SpaceX bought those two deep-sea oil rigs they named Phobos and Deimos, though they eventually decided the overhauls needed would be too expensive and sold them on.
Before them was the... SeaDragon(?) - which was never actually built, but on paper I think it was supposed to be even larger than Starship, and would be floated out to sea with the engines tightly covered, tilted vertical, and then fired with the engines well underwater, burning away the cover and relying on the pressure of the exhaust plume to keep the water away from the engines until it flew free.
Floating launch platforms would let them launch from almost anywhere, since there are very few places on land that a sufficiently large and isolated launch facility could be built, politically. After all they need to be on the coast for safety, so that they can launch over the ocean and not rain debris on peoples heads in case of an abort. And coastal land tends to be extremely valuable and politically entangled. As I recall, Boca Chica was pretty much the *only* place in the US, other than Cape Canaveral, where a sufficiently large launch facility could realistically get approved.
For context - people 30 miles away from the Starship launch reported their whole house rattling from the sound. Not something the sort of wealthy communities that tend to congregate along the coast are going to permit anywhere nearby. Especially not when SpaceX is aiming for weekly Starship launches, if not multiples per day.
And SpaceX has aspirations of operating a suborbital passenger line - carrying passengers halfway around the world in 20-40 minutes for the price of a first class airline ticket, with the bulk of the flights duration being a zero-g "space tourism" experience as it coasts unpowered above the atmosphere. For which they need launch/landing facilities close to the major population centers of the world - something that will never happen on land, but would be much more politically feasible on launch platforms dozens of miles out to sea.
As for whales... sound travels much better through water than air - many whales can communicate with each other from opposite sides of the ocean, and Starship will be vastly louder than any whale. I'm not sure what the minimum safe distance would be, but I suspect it'd be dozens if not hundreds of miles. And how are you realistically going to warn whales off? Perhaps military sonar slowly increasing in volume to give them a chance to flee - but that's going to take a lot of power, and potentially several (dozen) hours. If launches occur frequently the affect could be to completely deny whales access to huge swaths of the rich coastal waters they rely on - and deny the coastal ecosystem the beneficial influence of the whales.
(Score: 2) by JoeMerchant on Tuesday April 25, @03:17PM (5 children)
Thinking about the deluge system, I would have thought that it's basically supplied by water towers (elevated pools, whatever) that open the valves to let it flow. Half a million gallons is on the order of an olympic swimming pool, just gotta elevate it enough for the desired pressure / flow rate, and with big delivery pipes that pressure might be surprisingly low - maybe 20-30 feet of elevation?
Now, I can totally see the local water system not wanting to fill an olympic pool or two per launch (attempt), but there's desalinization for drinking, and there's more or less desalinization for equipment preservation which presumably comes with much lower cost per gallon...
We built a pneumatically powered widget for use in hospitals, it consumed quite a bit of air. The MD setting the design outline started off with: "Well, there's compressed air right there at the head of the bed, let's use that." Problem 1: it's only 50 psi and our widget barely worked at 45 psi, really was happiest in the 90-120psi range. Problem 2: that's medical grade breathing air, no oil - we'd actually want to add an oiling system if we were to use medical air to drive our widget long term. Problem 3: medical grade breathing air is actually rather expensive to supply: filters, oil-less compressor delivery, etc. The facilities manager tracked us down the first day we tried it and gave us a rundown of all the differences between his medical grade air we were consuming at a rate similar to 100 beds on ventilators and the 5hp compressor we had been using back at the shop. It wasn't impossibly expensive, but it was much more than 10x as expensive to use medical grade air than just BYOC (Bring Your Own Compressor.)
Україна досі не є частиною Росії Слава Україні🌻 https://news.stanford.edu/2023/02/17/will-russia-ukraine-war-end
(Score: 2) by Immerman on Tuesday April 25, @03:54PM (4 children)
I'm not sure that the "grades of desalination" you're thinking of is a thing. I believe the typical desalination approaches amount to either reverse osmosis (forcing water through a salt-blocking "filter") or something like highly optimized distillation. Either way, there's not really any way to only remove most of the salt - either it removes the salt or it doesn't, there are no steps in between.
You could perhaps dilute the pure water with saltwater... but I think *any* significant amount of salt is a problem - it eats away at everything like road salt does to a car's undercarriage, only in extreme fast-forward because of the extreme temperatures.
And yeah, the city is just not capable of providing enough water to fill an olympic swimming pool on a semi-regular basis. At about 70 gallons per capita day, every pool worth is enough to support about 21 people for a year. And half a million gallons is for the SLS - SuperHeavy produces about 9x the thrust. If water consumption scales with thrust (no idea) you can bump that up to 190 people.
Not inconsiderable for a city of 37k, especially when SpaceX has made clear that they intend to make hundreds of launches per year in the not-too-distant future - that could be over half their entire water supply. I'm sure they have no interest in even letting SpaceX get their foot in that door. Not with the way Musk has consistently gotten approval for for one thing, built a much larger thing, and then heavily pressured politicians and regulators to approve the bigger thing.
(Score: 2) by JoeMerchant on Tuesday April 25, @05:51PM (3 children)
Knew a guy whose wife's cousin ran a fish farm outside San Antonio - he followed all the legal processes and agricultural incentives and setup a profitable tilapia farm, which consumed more water than the entire city of San Antonio (direct from the aquifer). When the droughts hit, they bought him out, imminent domain, to stop the operation.
Україна досі не є частиною Росії Слава Україні🌻 https://news.stanford.edu/2023/02/17/will-russia-ukraine-war-end
(Score: 2) by Immerman on Tuesday April 25, @06:00PM (2 children)
And the moral of the story is "waste massive quantities of water at your own risk" - if it becomes a problem the communities you impact WILL solve it.
Though I suspect SpaceX would be FAR more difficult to buy out... way too much money and powerful political connections, so they would very likely be able to force the community to leave.
(Score: 2) by JoeMerchant on Tuesday April 25, @06:09PM (1 child)
>they would very likely be able to force the community to leave.
Like they're already doing to the wildlife in the preserve where they located the launch pad.
Україна досі не є частиною Росії Слава Україні🌻 https://news.stanford.edu/2023/02/17/will-russia-ukraine-war-end
(Score: 2) by Immerman on Tuesday April 25, @06:31PM
Yep. [sigh]
(Score: 2, Interesting) by khallow on Tuesday April 25, @04:40AM (8 children)
Well, what's wrong with the approach? The problem here is that the NASA approach doesn't actually tell you what happens (except in the cases where NASA actually wets that finger - NASA is notorious for being very confident about the things they don't know, backed by computer simulation and such). Now SpaceX knows. Similarly, the steel plate can only go wrong once. My take is that they can play around with these concepts using a Falcon 9 launch. Perhaps they did that already and got it wrong due to the higher power of the Super Heavy.
(Score: 2) by RS3 on Tuesday April 25, @05:23AM (6 children)
Looks like you answered your own question. :) Good work!
Like I said above somewhere, I'm big on experimentation, but it seems they've learned enough to know what would happen with a bigger rocket. I dunno, makes me wonder what goes on at SpaceX and NASA.
My pure "gut" right-brained hunch is the water in the steel plate will flash to steam. Pretty sure they'll have pressure reliefs, the steam will leave and the plate will vaporize.
Maybe part of the calculated risk is they'll say they need more taxpayer money to fix these things...
(Score: 1) by khallow on Tuesday April 25, @05:31AM (1 child)
Who is they? There's a good chance that nobody living (and perhaps nobody dead!) has tested a large rocket without water suppression systems. In which case, you're operating from written studies that don't address your situation well. Further, if this really is a case of SpaceX leadership ignoring historical data, then the launch just checked that hubris.
(Score: 1) by khallow on Wednesday April 26, @03:57AM
I forgot about Space Shuttle damage [nbcnews.com] to launch pads. The story is to an unusual bout of damage caused during the launch of Shuttle Discovery. When a big rocket like that can move 5300 bricks with a water deluge system absorbing a bunch of energy, it clearly can move a lot more without.
(Score: 2, Disagree) by Immerman on Tuesday April 25, @03:22PM (3 children)
I'm pretty sure SpaceX has taken zero taxpayer dollars for basic rocket development to date, why are you so quick to accuse them of it? They've funded their R&D by selling launches to the government, but cash for services is a *very* different beast than the "pay us to study/solve the problem" that plagues the traditional aerospace industry.
They *have* been awarded some milestone-based government R&D money under the Artemis program to develop the Lunar Starship variant and assist with developing orbital refueling, but I believe that's the first time that's happened. It's only very recently that they've gotten anything more from NASA than a grudging "fine, we'll buy your launch services, but only because you're so much cheaper than the alternative, and will shine the media spotlight on our corrupt relationships with the traditional aerospace giants in court if we don't"
(Score: 2) by RS3 on Tuesday April 25, @03:58PM (2 children)
"accuse"? You're way misinterpreting me and overreacting a bit (to your own misinterpretation). Why do these blogs and forums bring out so much negativity and hostility? Everyone is a mind-reader I guess, but you got it wrong this time. Next time maybe please ask for clarification? I'm NOT a writer, rather, an engineer, and we're famous for being less adept at verbal skills.
1) I in no way complained nor "accused". I'm in favor of science and NASA and taxpayer funding thereof. If We the People were polled on what our tax dollars are spent on, I'd vote for more $ toward science than are currently spent.
2) NASA buys goods and services from SpaceX, so...
3) See #1.
I'd sure like to see more cooperation, collaboration, and coordination, and less competitiveness in the world.
(Score: 0, Troll) by khallow on Tuesday April 25, @05:07PM (1 child)
Let's review:
"More taxpayer money"? That's accusation through implication. You can't have "more" if you didn't have some in the first place.
First, there's a serious grievance here against NASA - namely that they've held back [soylentnews.org] space development by decades (TL;DR: 9 year monopoly followed by 10+ years of a stagnant NASA-enforced oligopoly on launch providers leads to no serious improvement in the orbital launch market for three decades). I'll note that I've heard similar things from other markets such as small satellite launch market (where In a later post in that thread, here's my view on the value of NASA over the past 50 years.
NASA isn't about science or progress, it's about money spent in the right congressional districts and military industrial complex care and feeding. There's a whole lost generation of people sore about that. Sure, there's a lot of waste in US government spending (which a lot of people are strangely comfortable with), but that doesn't excuse something that's so heavily anti-science and anti-progress. We should have standards.
My take is that we've done so little in space over the decades precisely because competitiveness has been neutered. Everyone who was anyone had their own piece of cheese. In exchange, they didn't rock the boat by actually doing anything. That started to change in the mid 1990s when the Pentagon spurred competition with its Evolutionary Expendable Launch Vehicle program. And it got dialed up to 11 when SpaceX showed us how it's done.
I get there's a bunch of people huffy over why a launch failure from SpaceX generates more buzz than a successful launch of SLS. It's because we can tell already that Super Heavy will be a game changer for humanity, while SLS will be a dead end.
(Score: 2) by Immerman on Tuesday April 25, @06:03PM
Thank you, you beat me to it.
(Score: 2) by Immerman on Tuesday April 25, @03:26PM
I don't think a Falcon 9 launch can tell them much that's useful. I mean, even the old unreinforced pad held up fine to multiple Starship launches, and that's like 3x the thrust of a Falcon 9.
(Score: 2) by ElizabethGreene on Tuesday April 25, @04:39PM (2 children)
I am not a rocket scientist.
Looking at the photos of the launch crater, a few things stand out to me. Most of the concrete's steel reinforcement appears undamaged. The pylons supporting the launch structure also appear mostly undamaged. The excavation beneath the pad reveals a significant amount of sand and small boulders. My intuition, and I don't have any data for supersonic flow conditions at thousands of degrees, is the vibration caused the concrete to fail and that turned the kit into a giant sandblaster.
If steel can take the vibration to prevent that failure mode, I *assume* the heat transfer would be comparatively small given the high exhaust velocity. Also, the engines run fuel rich so I wouldn't expect the steel to burn.
I wonder if "What's the least launch infrastructure we need?" is a question they needed to answer to draw a box around the economics of surface-to-surface suborbital operations?.
(Score: 2) by JoeMerchant on Tuesday April 25, @06:16PM
What would you be moving surface to surface suborbitally with a BFR?
I agree, this seems like it was a "let's try to find a new bottom" call in terms of launch systems costs.
My gut feeling is that the substrate below the concrete probably didn't help matters. A lot of the Texas Gulf coast has a soil type referred to as "Gumbo" - lots of fine silt from rivers, particularly the Mississippi, and it shares many structural properties with Jell-O. Get that soil vibrating at high amplitude under the concrete and concrete won't be in compression half the time. I certainly hope they took seismic recordings.
Україна досі не є частиною Росії Слава Україні🌻 https://news.stanford.edu/2023/02/17/will-russia-ukraine-war-end
(Score: 2) by Immerman on Tuesday April 25, @06:28PM
A lot of it is probably the sound - as I recall the primary purpose of a water deluge system is to absorb a ton of the launch energy to boil the water, rather than having it emitted as insanely loud sound waves that will rip stuff apart. There are reports from people 30 miles away from the Starship launch whose whole house was shaking from the sound. I can only imagine what it was doing at ground zero.
Keep in mind that the engines are specifically designed to handle the insane temperatures of rocket exhaust, are actively cooled with the cryogenic fuel feeds on their way to the turbopumps, and (usually) further insulated from the heat of with a layer of oxygen-free non-burning fuel lining the interior of the combustion chamber. And it's *still* a challenge to avoid "engine-rich exhaust" from the engine burning itself up (the green streaks somewhat common in the exhaust of early Starship test flights).
The heat probably won't be able to quickly penetrate far into the steel, but it won't need to - the top layer of steel will likely rapidly burn away, exposing the deeper layer to do so in turn.
Then again, the launch pad pillars *seem* mostly okay, so it might be fine. Though it's hard to tell just by looking if the steel shielding actually burnt most of the way through or not - we'll have to wait and see if they replace it before the next launch.
(Score: 2) by istartedi on Tuesday April 25, @05:26PM (3 children)
As majestic as a fully rocket powered liftoff is, it burns crazy fuel just to get to max-Q. I haven't been thinking of springs. I've been thinking of electrically powered linear accelerators, like they use on some roller coasters. Now imagine the scenarios, which certainly involve some massive engineering and construction, but if you're blasting launch complexes and you're a billionaire why not?
1. A straight underground tube. Excavate maybe 1km down, not in Florida. Too wet. In Texas? Not sure about the geology of the bedrock around the current launch sites. The excavation is massive, but silos are a time tested technique for smaller rockets like ICBMs, they're just not accelerated. The rocket needs to be able to hold up to the push from the accelerator in the tube, gas has to be evacutated quickly just like on a conventional pad; but you can run low throttle on the way up and then go full throttle after exit.
2. Mountain-side track. No excavation needed, basically a scaled up mega coaster accelerator, but I'm not aware of anybody doing it.
Both of these require you to store massive electric energy and deliver a huge surge of power to the electro-magnetic sled that pushes the rocket, but guess who loves big battery storage?
The harder thing is abort scenarios. The nice thing about a rocket-powered liftoff is that you know the rocket has enough thrust to clear the pad. With an assisted launch, you get in big trouble close to the ground if the rockets don't generate enough thrust after the assisted phase.
I think that (aside from the scale of construction) might be the reason why we still blast pads with rocket exhaust, except for the smaller rockets; and of course the sub-launched missiles which may get some assist from buoyancy but I don't think it makes that much of a difference. In that scenario, the ocean is more useful for cooling. No need to worry about the sub getting roasted.
Appended to the end of comments you post. Max: 120 chars.
(Score: 2) by RS3 on Tuesday April 25, @06:33PM (1 child)
Being an EE, I like it. Giant rail gun. Already well established. Yes, there's another Musky company that knows some things about energy storage, and look at that, motors. Once the rocket is up high enough riding on its own plume, you can drop off the armature parts.
I'd still like to see them use a plume deflector like the good old days, and water spray. I'm sure they could improve the efficiency, but I understand water supply is a problem. I'm a fan of solar power, so a solar powered evaporation system might work, but I don't have the numbers for scale. Like how big would evaporative water collectors have to be to supply enough water for the launches?
Back to the rail gun, yes, I wouldn't start the linear motor launch and release the rocket hold-downs until the engines were all performing properly. Just like the Saturn V...
(Score: 2) by istartedi on Tuesday April 25, @09:34PM
I didn't about aircraft carriers until after I saw your reply. I was EE too, but ended up doing all software. I too still have a soft spot for analog circuits and massive surges of power, even though I never worked with it professionally. Anyway, what do you think of the new electric catapult systems on the Ford class carriers? It's launching jets of course, and they are holding those at full throttle even before launch because, once again, no danger of melting the ship. Scale. It's all about scale.
Appended to the end of comments you post. Max: 120 chars.
(Score: 1) by khallow on Wednesday April 26, @04:47AM
There's several issues. First, the launch environment is immensely destructive. Your linear accelerator has to deal with that. One option would be to hurl the rocket well above the launch padand then ignite. That would also greatly reduce the need for energy suppression systems on the launch pad as well.
But that option leads to the second problem - that rocket engines don't ignite and go to full power in a fraction of a second. A typical launch sequence is to let the engines burn for about five seconds to build to full power. So your linear accelerator would have to push the rocket to about 125 m/s (plus air resistance losses) in order to give enough time to ignite and thrust.
Then there's the third problem: you're committed if you push that rocket into the air. Any engine shutdown at this point is a scrub and your fully fueled rocket will come down somewhere.
Having said that, we have a real world example of a rocket that can ignite after it's kicked off a launch pad, the MX "Peacekeeper" missile [nps.gov].
Also, note the term for the launch process is "cold launch". The first stage was a solid propellant motor which both ignites fast and is very reliable.
A possibility then is to use disposable solid rocket boosters (SRB) to give the rocket enough time for its liquid fuel rockets to power up (they could taper their thrust so they drop in power as the main rockets increase). It wouldn't need to be that long, no more than 15-30 seconds. So in effect, the first stage would be these boosters (which can be side mounted and dropped shortly after use).
Given that the main rocket engines are the control system, maybe we could do a "lukewarm" launch where several engines are lit at start at considerable throttle (lower power), then the linear accelerator kicks the rocket up and the SRBs ignite. The rest of the main rocket motors are then ignited.
Alternately, you either harden the linear accelerator so that it can take the environment somehow with modest repair. Or make it disposable. Given the economics of reusability, I don't favor that last option.
Anyway, we see the two features of this sort of launch: a significant initial velocity which boosts available payload and less drama on the launch pad.
(Score: 4, Informative) by takyon on Monday April 24, @07:04PM
Here's a better article:
https://arstechnica.com/science/2023/04/so-what-was-that-was-starships-launch-a-failure-or-a-success/ [arstechnica.com]
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 4, Interesting) by squeedles on Monday April 24, @08:03PM (5 children)
Yea, not a surprise that it was deliberately destroyed, that's range safety's job.
What I found interesting was that the booster engines kept firing through the entire pitch up ... and up ... and oops, still more up, maneuver. My understanding was that they were supposed to have MECO once they started pitching. I saw some reports about not making velocity or altitude targets because of the inoperative engines, so perhaps there were some conflicting software states in the flight control.
In any case, as long as those engines are firing there is going to be some axial force, and I can see that interacting with other sensors to keep clamps from releasing, preventing the stage separation. I was frankly amazed that it did 270 or 360 without failing -- strong beast!
Looking forward to whatever post-mortem details they eventually release.
(Score: 5, Funny) by ElizabethGreene on Monday April 24, @08:34PM (2 children)
My extensive experience in Kerbal Space Program leads me to believe the problem was too many struts. :)
(Score: 2) by richtopia on Monday April 24, @11:37PM (1 child)
And we can solve it with more struts!
(Score: 3, Funny) by ElizabethGreene on Tuesday April 25, @03:26PM
We'll just jump back to the quicksave on the launch pad, revert back to the VAB, and remove the struts connecting the non-falling-off bit from the falling off bit. Easy fix. You remembered to quicksave on the launchpad, right?
(Score: 2) by Immerman on Monday April 24, @08:45PM (1 child)
I do wonder if maybe an engine "failed on" - it did seem like one just kept going and going, and the flame didn't look too healthy.
But that was at least a 1260! I counted roughly 3.5 revolutions before it finally blew up.
And judging by the camera feed from the inter-stage section, it was holding together just fine the whole time - I didn't notice anything flexing or shaking. Of course they were also in near-vacuum at that point, so aerodynamic stresses would have been minimal.
(Score: 3, Interesting) by JoeMerchant on Monday April 24, @11:12PM
I read elsewhere that several engines are presumed to have failed due to debris blowback, not unlike the minivan that was totalled at quite some distance from the launch pad (can we say: range safety failure?)
I would expect many kinds of engine failures when they are being blasted with sand, rock, chunks of concrete, rebar, etc. Most of the debris was pushed away by the thrust, but apparently not enough of it.
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(Score: 4, Insightful) by Billy the Mountain on Monday April 24, @08:46PM (1 child)
It's my understanding that the rocket was too low in altitude for stage separation so they probably did not even try to separate them.
It IS true that the ship needed to roll to achieve stage separation but I believe the rolling observed was the ship going out of control due to loss of engine gimballing, and the loss of gimballing was due to hydraulic failure. And the hydraulic failure is possibly due to damage sustained during the unanticipated flying debris that occurred close to the ground.
(Score: 2) by Immerman on Monday April 24, @09:31PM
Hmm, sounds plausible, where'd you hear that?
It'd also be practically best-case scenario, since the hydraulic gimballing has already been replaced with electric systems in the newer boosters.
(Score: 2, Interesting) by pTamok on Tuesday April 25, @06:49AM (5 children)
I strongly suspect 'a bunch' of well-qualified rocket scientists and engineers will be looking at the available data, and I wouldn't listen to much to off-the-cuff statements by Mr. Musk.
The launch-pad engineering problem is interesting. How cheaply can you build one that works successfully ( (semi-)ballistic debris destroying engines is non-optimal). It's relatively easy to conceive of expensive systems that mitigate/solve the problems, but if your ambition is a high frequency of launches, you don't want to have to do extensive repair and/or water desalination between each launch*. You also have a nod towards landing and launching again from unprepared surfaces on the Moon and/or Mars. A successful colony may well need a well-engineered pad as a priority.
*I wonder if a deliberately engineered sufficiently thick layer of cheap ablative material might work. A pit with sides sculpted in such a way that ejected debris is directed away from the rocket (a hyperbola with the rocket at the focus), covered in a thick layer of deep-frozen (liquid nitrogen temperature) water ice (or maybe carbon-dioxide). Or launch over a lake of liquid nitrogen - in bulk, it's commercially available at 50 cents per gallon, and I'm sure SpaceX could produce it itself for much cheaper..
(Score: 4, Informative) by sjames on Tuesday April 25, @07:32AM (4 children)
No liquid nitrogen necessary here or even useful. When liquid nitrogen is heated, the process of vaporization absorbs 199 joules per gram (the heat of vaporization). By contrast, water absorbs 2260 j/g, so water is much more effective for removing excess heat above the boiling point.
If you start with ice, melting it takes 334 j/g (heat of fusion), then it heats up 100 degrees absorbing 400 j/g, then boils absorbing another 2260 j/g.
So at only 199 j/g for nitrogen, the performance is terrible even compared to just dumping room temperature water on it.
Meanwhile, ice has a capacity of only 2 j/g, so warming ice at liquid nitrogen temperatures up to 0C is only another 390 j/g. So the liquid nitrogen cooling the ice only gets you a 13% gain for a lot of extra time, trouble, and cost. Freezing the water at all doesn't bring all that much to the party either and adds a lot of cost.
The only reason liquid nitrogen works out for cooling a CPU in a crazy overclocking stunt is that the CPU needs to be a little below 0C to run that fast, but you need a phase change to remove that much heat from a small area. If 100C was OK for the CPU, water would be the better choice though the videos would be less spectacular.
(Score: 1) by pTamok on Tuesday April 25, @02:08PM (3 children)
I take your point, if you look at heat capacities, it's terrible.
The specific heat capacity is joules per kelvin per kilo (J⋅kg−1⋅K−1), so it's the amount of energy you need to put in to get a one kelvin increase in temperature, so while the phase change from solid to liquid water is 334 kJ/kg, and the phase change from liquid to gas is 2260 kJ/kg, the specific heat capacity is 4.2 kJ/kg/K, so transitioning a kilogram of ice a zero degrees centigrade to steam, at 100 degrees centigrade requires 334 + (4.2x100) + 2260 = 3014 kJ. (See also: Omni Calculator: Water Heating Calculator [omnicalculator.com])
The phase change from liquid nitrogen to gaseous nitrogen is, as you say 199 kJ/kg, which is roughly six-and-a-half percent of the value we calculated for producing steam from ice.
But the a benefits of nitrogen is that it is environmentally benign. Producing millions of gallons of desalinated water generates a lot of brine. Water's also rather a good solvent, and promotes corrosion. Nitrogen, on the other hand, you pull from the air. No brine to dispose of. Doesn't hang around seeping into places it is not needed, and given it's not solid (unlike ice at the same temperature), there are not chunks of it around to cause problems when flung around semi-ballistically. The fact that it is cold is not that important: it is an inert, environmentally benign liquid.
Sure, putting a lake of liquid nitrogen under a rocket sounds crazy. But also cool. It's simply there to stop the exhaust from ripping up the ground. And it auto-disposes itself.
It might even be fun to watch.
(Score: 0) by Anonymous Coward on Tuesday April 25, @03:46PM
I see what you did there.
(Score: 2) by sjames on Tuesday April 25, @08:09PM (1 child)
If you look at the energy required to liquefy that nitrogen, it is a lot less environmentally friendly unless you use solar power. If you DO use solar power, then just reduce that brine to salt and sell it in gourmet stores as sea salt to defray costs.
If you need a million gallons of water, you'll need over 12 million gallons of liquid nitrogen.
Also consider how much the concrete will not enjoy the temperature swings involved in liquid nitrogen.
(Score: 1) by pTamok on Wednesday April 26, @10:41AM
I'm not sure the market for gourmet salt is that big. Grin.
Why use concrete? A large steel holding tank (the size of a supertanker dry-dock) would be fine.Vaporizing concrete is a bad idea. Vaporizing liquid nitrogen is a "shrug, so what?". Why use nitrogen instead of water ?- you don't have the decontamination and disposal problems afterwards. There's already a cryogenic facility for producing the fuel. Scaling up to produce thousands of cubic metres of liquid nitrogen is just engineering, no breakthrough is needed.
It's just a way of coping with the rocket exhaust - you don't need something solid to push against - a large chamber of air (or vacuum) underneath would do just as well. The engineering problem is that the rocket is designed to be supported from the bottom, so the supports need to survive the blast for long enough to allow the rocket to be self-supporting. Another way would be to suspend the rocket from several towers with something high-tensile - Kevlar maybe - and have the space under the rocket as empty as possible - that is, the rocket is suspended over a cavern big enough that the hot supersonic gas doesn't do any damage until it can be managed.
The traditional approach is blast deflectors and water cascades. We've seen the photographs of what the launchpad looked like after the launch, so SpaceX is either going to need a bigger boat, or another approach. The launch cadence aimed for does not allow for extensive launch facility repair between launches. (High-strength) concrete takes a long time to cure. A depleted tank of inert liquid just needs refilling. A supersonic jet of superheated gas directed into a super-tanker dry-dock full of liquid nitrogen might look spectacular, but there's nothing to break, and no debris to kill engines, and once the rocket has gone, no repairs: just top it up.
(Score: 2) by Thexalon on Tuesday April 25, @11:03AM
(loses control of his horse and falls off)
"Nobody panic! That was deliberate, that was deliberate!"
The only thing that stops a bad guy with a compiler is a good guy with a compiler.