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SpaceX is attempting a huge feat in spacecraft engineering. It is seeking to land the first stage of its Falcon 9-R rocket on a floating platform at sea. Normally this would end up at the bottom of the ocean. If successful, SpaceX will shake the rocket launch market, by shaving millions of dollars off launch costs.
Today’s rockets are one shot wonders. They burn up fuel in a few minutes and splash down into terrestrial oceans, having put their payload on the right trajectory. This is wasteful and that is why scientists have dreamed of building reusable launch vehicles.
The holy grail of rocket launchers is a concept referred to as the single stage to orbit (SSTO) vehicle. The idea is to use a reusable launch vehicle (RLV) which has the capability to deliver a payload to orbit, re-enter the Earth’s atmosphere and land, where it can then be refuelled. The process can then be repeated with a short turnaround.
https://theconversation.com/explainer-why-reusable-rockets-are-so-hard-to-make-36036
(Score: 1, Interesting) by Anonymous Coward on Sunday January 11 2015, @08:23PM
What a fascinating idea. Perhaps some kind of "shuttle to space" could be arranged.
(Score: 2) by Nobuddy on Monday January 12 2015, @08:41PM
The space shuttle uses non reusable booster rockets as their primary lift source. Same issue, different payload.
(Score: 3, Insightful) by VLM on Sunday January 11 2015, @08:37PM
The author in the linked article does a decent job of explaining that its really hard along with a lot of "trust me" because anything other than "trust me" would require math and that is forbidden from mass market articles. Which is too bad.
However... author could have played some games with analogies.
Almost all the money is spent on R+D and oversight and management and analysis, so the one percent or so of hardware costs is a rounding error. So the obvious analogy is its like freaking out about a medical doctor throwing away a used bandaid rather than finding a way to re-use bandages, after thinking about the six figure cost of education and six figure salary a 25 cent band aid isn't very much (also the risks of re-using bandaids is kinda high)
Making them reusable would make them heavy and if cost scales with a high polynomial of mass due not just to material cost but handling and design work, then its cheaper to make a pile of small disposable rockets than to invest the staggering cost of an incredibly heavy reusable rocket until you hit a crossover point. I'm not sure which is a better analogy of the opposite of the disposable condom, either an imaginary re-usable one made of iron pipe pieces from home depot weighing 2 pounds, or getting a vasectomy. In either case, a disposable solution is actually cheaper and more convenient on an overall system basis than the alternative non-wasteful solution.
Finally you could whip out an analogy revolving around paper plates vs finest china. If you know the neighbor brats are going to break about 2% to 5% of all the dishes you give them, the overall cheaper systemic solution is to use paper plates rather than your finest imported collectable china plates. In a world where a reusable vehicle fails and kills everyone on board about 1 in 50 missions while costing far more than twice as much to operate and 100 times as much to develop as non-reusable, its a hard financial sell. Especially when the non-reusable competition fails and kills the crew much less often than 1 in 50 missions. It would be like making re-usable ICBMs or re-usable naval torpedos, it just doesn't make sense once you understand the operating conditions and odds of re-usability. You can be as proud as you want of the theoretical re-usability of the engine in a nuclear ICBM, but its probably not going to get many uses anyway under normal operating conditions, and if it costs 10 to 100 times as much as a non-reusable ICBM engine, you're probably better off using the disposable one time use engine.
(Score: 3, Insightful) by frojack on Sunday January 11 2015, @08:59PM
The author in the linked article does a decent job of explaining that its really hard along with a lot of "trust me" because anything other than "trust me" would require math
Perhaps this is true, but there was a lot of "trust me" in your post as well:
so the one percent or so of hardware costs is a rounding error.
One percent might be the cost of materials, raw steal, aluminium, etc.
But the fabrication and construction costs are significantly higher than that.
Design costs probably can't be avoided. But they are spread over the life of the design, and are going to be there anyway.
So ALL that matters is the total cost to build a new one, vs the total cost to refurbish a used one, plus any putative additional fuel costs to launch a reusable vehicle vs a one shot device.
Early space programs didn't have the ability to recover vehicles, so it pretty much wasn't an issue. The shuttle changed that. Space X changes that. Spaceship One changes that. Return and reuse is going to be the new norm.
No, you are mistaken. I've always had this sig.
(Score: 4, Informative) by TheRaven on Sunday January 11 2015, @09:45PM
sudo mod me up
(Score: 2) by frojack on Sunday January 11 2015, @09:54PM
Pretty sure both I and VLM addressed refurb costs.
Pretty sure that rocket reputability [nasa.gov] has already been proven. Without teleporters.
No, you are mistaken. I've always had this sig.
(Score: 2) by frojack on Monday January 12 2015, @05:04AM
sigh... Rocket Reuse-ability
No, you are mistaken. I've always had this sig.
(Score: 2) by Adamsjas on Sunday January 11 2015, @10:52PM
Ok, I assume you were kidding about the teleporting part.
But If I can play along, why would we teleport rockets down but not up? Of if we had teleporters why would we even have rockets?
(Score: 2) by deimtee on Monday January 12 2015, @10:33AM
I think he was making the point that most rockets wouldn't be re-usable after a single launch, even without the stress of dropping back to earth. He doesn't actually have a teleporter
No problem is insoluble, but at Ksp = 2.943×10−25 Mercury Sulphide comes close.
(Score: 2) by VLM on Sunday January 11 2015, @10:02PM
Something interesting to consider about the design costs, is $0 was spent on reuse design work on the Falcon 1 which puts it at a competitive advantage over a theoretical 1-R where money was spent on re-use.
In the NASA world, things change very slowly, but spacex has already stopped using the Falcon 1, Falcon 9 V1.0, and is almost done launching the Falcon 9 V1.1 and the 9-R will fly "soon ish". Having to keep "antique" reusable Falcon 1's, 9 1.0s and 9 1.1s around for 20 years until a mishap or whatever would be very problematic in the development cycle of the 9-R.
Its interesting that the model T was not the first car, not by any means. It was the first mass produced car in the USA, thats all. Might be that the tech level isn't quite ready for the model T of the space booster world. There were cross country car races 30 years before the first model T rolled off the line.
(Score: 2) by Immerman on Tuesday January 13 2015, @12:03AM
Hell, for that matter there were electric cars competing in races almost 70 years before the model T was designed.
The model T's claim to fame was that it was cheap and reliable enough to be a good investment for members of the middle class. Something that the previous mass-produced Models A, B, C, F, K, N, R, and S had not achieved (and those are only the previous models produced by the Ford Motor Company, which was hardly without competitors)
(Score: 2) by kaszz on Monday January 12 2015, @12:26AM
Given enough launches the re-usable rocket will eventually reach break even. And even if materials get fatigued, perhaps the most valuable parts are the different machines like pumps, steering, nozzle etc.
(Score: 2) by mhajicek on Monday January 12 2015, @05:07AM
The hard part is detecting the fatigue so parts an be replaced before causing a failure.
The spacelike surfaces of time foliations can have a cusp at the surface of discontinuity. - P. Hajicek
(Score: 0) by Anonymous Coward on Monday January 12 2015, @02:52AM
Actually, manufacturing rocket engines is not cheap. It takes time. That's where most of the savings come from - no need to manufacture the rocket against and again. Base material costs don't matter as much as manufacturing part.
Making them reusable would make them heavy
I think SpaceX is countering that idea already.
Anyway, old rockets were not reusable because guiding them for a landing was simply not practical at all which would increase mass.. Only modern computers make this possible (and I'm talking last 10-years of computers, not last quarter).
(Score: 2) by mhajicek on Monday January 12 2015, @05:11AM
Rocket engine manufacturing costs are coming down though. Hybrid additive / subtractive machines are maturing, and greatly facilitate the production of otherwise difficult geometries in any alloy desired.
The spacelike surfaces of time foliations can have a cusp at the surface of discontinuity. - P. Hajicek
(Score: 2) by Immerman on Tuesday January 13 2015, @12:09AM
Actually, I may be mis-remembering, but as I recall the rocket itself is something like 90-95% of the cost of a typical launch. Fuel is another percentage point or two, and the remainder covers the logistical and bureaucratic overhead you're so quick to blame for the majority. Of course that's after the design costs have been amortized over many rockets, but SpaceX doesn't seem to be having too many problems competing, despite refining their designs almost continuously.
(Score: 2) by VLM on Tuesday January 13 2015, @12:21PM
Can't get a launch without a launch program. Launch programs are rather expensive.
Something to think about is the raw steel and plastic in a car is always less than $5K often much less, and the factory floor labor is always less than $2K, cars require almost no labor to manufacture. Why any cars cost more than $7K or so is exercise for reader.
(Score: 4, Interesting) by frojack on Sunday January 11 2015, @09:05PM
The point overlooked here is that Space X landed on a postage stamp floating in the ocean. Landed too hard, but landed never the less.
Now, launching from the west coast is starting to make more sense, if the booster can have an entire desert to land in, rather than a pitching deck of a barge.
No, you are mistaken. I've always had this sig.
(Score: 2) by gman003 on Sunday January 11 2015, @09:50PM
The plan is to ultimately return to the launch facility. They're doing sea-landing tests to prove the rocket can safely fly under its own power at low altitude, so the FAA will let them return to US airspace (this is a valid concern - a large rocket is basically a flying bomb, and we don't want that flying overhead without knowing it's safe).
(Score: 2) by nitehawk214 on Monday January 12 2015, @03:53PM
I have heard this a few times before, but I still don't understand how the first stage could return to the launch pad. Isn't the thing travelling east at supersonic speeds? How would it have enough fuel to cancel all of that velocity and return to the pad?
Perhaps it is more of a trajectory thing. If the first stage is going more "up", than "east", perhaps it could be possible. Does anyone know how far off shore and downrange the landing ship was? I could not find any info about it.
"Don't you ever miss the days when you used to be nostalgic?" -Loiosh
(Score: 3, Insightful) by subs on Monday January 12 2015, @04:37PM
Energetically, a full turn-around and fly-back is just about doable, provided you accept that very little of your launch mass makes it to orbit. Also, you are correct that on a reusable launch, they fly a much steeper trajectory. Normally a rocket's trajectory passes the 1:1 altitude-to-downrange distance ratio at around the 25-30km mark. Here they flew to well over 60-70km altitude before the 1:1 ratio. A steeper trajectory has the disadvantage of losing more energy to gravitational drag, but it reduces the lateral speed at stage separation, which is obviously important here. Another thing to consider is that after the 2nd stage separates, a good 80% of the remaining mass of the vehicle is gone, so what little remaining fuel is left in the first stage is going to give you a lot more delta-V than it would have with the 2nd stage still attached.
Even so, if they manage to pull it off for real, it'll be a huge achievement. There's no doubt in my mind in that if they manage to reuse the 1st stage a few times, the resulting dramatic decrease in launch costs will basically signal "game over" for all the other launch providers competing in the same market segment. SpaceX would be able to basically undercut them by about 10x.
(Score: 2) by nitehawk214 on Monday January 12 2015, @10:00PM
Ahh, I did miss a critical part there. An empty rocket is much lighter than a fully fueled one, and since the second and third stages have broken off to fly away on their own, this reduces the mass greatly.
Also the steeper trajectory makes sense too. The first stage is trying to get the rocket out of the thick part of the atmosphere more than it is trying to impart orbital velocities.
"Don't you ever miss the days when you used to be nostalgic?" -Loiosh
(Score: 2) by subs on Tuesday January 13 2015, @03:28AM
Ahh, I did miss a critical part there. An empty rocket is much lighter than a fully fueled one, and since the second and third stages have broken off to fly away on their own, this reduces the mass greatly.
Just for perspective, a fully-fueled F9R with payload is about 510 tons on the pad. Of that, the second stage with propellant and payload is about 100 tons, while the dry mass of the first stage is only about 20 tons. So assuming you've still got around 20 tons of propellant in the first stage at separation, your vehicle mass suddenly drops from 140 tons to just 40 tons. That's also part of the reason why when they execute the turn-around burn they only burn 3 engines instead of the full 9 and only a single one for the final landing maneuver. Those things are immensely powerful and at such a low vessel mass could very well surpass the vehicle's structural g limits. F9 flight loading limit is around 5g, and considering each engine delivers a minimum of ~50 tons in vacuum (at 70% minimum thrust setting), firing all engines even at minimum thrust would easily give you 10g+ acceleration.
As for first stage purpose, you're partly right. While atmospheric resistance plays some role during launch, its effect diminishes rather quickly above ~15-20km altitude. Really, the main reason for staging in rockets is to get around the exponential nature of the rocket equation. To get to LEO, you need about 9000m/s of delta-V. Of that, only about 200-300m/s is expended on getting through the atmosphere. A good chunk (around 800m/s) is actually spent on working against gravity and lifting the vehicle so it doesn't come crashing down before you have time to accelerate up to orbital velocity - that's gravitational "drag". It's essentially the energy spent on "hovering" the vehicle over the ground while you're speeding it up sideways; this would be the same regardless if there were an atmosphere or not. That is not to say that you were wrong, just wanted to share my thoughts.
(Score: 0) by Anonymous Coward on Sunday January 11 2015, @11:47PM
oh! i hope it works!
i'm starting to pour a fire proof concrete slab in my back yard and sending the co-ordinates to amazon.
maybe they can "rocket-drone-send" me some bulky solar panels...
i wonder if the military would be interested in re-supply missions via rockets?
collect the rockets for re-use after the area has been secured : )
(Score: 1) by steveha on Monday January 12 2015, @05:10AM
The article seems heavy on the disadvantages of reusables. Additional weight and complexity to accommodate the reusability is the main one.
I don't buy the "additional complexity" argument. The control software would be more complex and that's about it. What SpaceX is doing is to land the first stage under controlled rocket power; so you don't really need any extra hardware (e.g. parachutes).[1]
But there are two major, major advantages to reusable: cost and reliability.
Cost is obvious. You build this giant rocket stage out of expensive metal alloys, with all the tanks and pipes and rocket engines and computers, and you pay a bunch of people for building it and quality-checking it; and then instead of destroying it you use it more times. Huge cost savings.
Reliability? With a single-use rocket you have to make brand-new rocket parts perfect the first time, and any mistake means your rocket can be destroyed. With reusables you can actually have a test flight, and as the rocket keeps flying you can get a track record of reliability.
One more advantage: once you have a fleet of tested reusable spacecraft, if you have a sudden urgent need to launch something, you can just prep and fuel and go. Right now we are very far from that.
I want to see space travel become boring and routine within my lifetime. That will never happen with single-use rockets, so I'm cheering on any attempts for reliability.
P.S. I have seen a couple of references to the Space Shuttle in comments on this article. Just because the Space Shuttle was insanely expensive and at the same time insanely dangerous[2] doesn't disprove the concept of reusable spacecraft. NASA got to the moon by iteration: fly something, measure how it worked, design something new, repeat. For the Shuttle, NASA attempted to design something in a single generation, and it was far from perfect. (In contrast, look at how SpaceX has been iteratively refining their stuff.) Also, the Shuttle was compromised by a weird requirement to be able to lift heavy things into a polar orbit, so its design favored heavy lift capacity over reusability.
http://en.wikipedia.org/wiki/Space_Shuttle_design_process#Air_Force_involvement [wikipedia.org]
[1] If you didn't plan to reuse the first stage, maybe you could use non-restartable engines and I guess for reuse you probably need to be able to stop them and start them... but I think most liquid-fueld rocket engines are restartable anyway.
[2] By actual statistics, the Shuttle was only two-nines reliable. Wikipedia lists 135 flights; two of those ended in complete destruction of the Shuttle and the deaths of all crew. That's a 1.5% chance of death per flight; if cars or airplanes were that unsafe, few would use them.
(Score: 2, Funny) by redneckmother on Monday January 12 2015, @06:51PM
"Physics 101: Gravity Works."
That's what I tell the grandchildren when they fall down or drop something.
So far, none of them has "parroted" that to a teacher, so none of them have been sent to the office.
Mas cerveza por favor.