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US military eyes nuclear thermal rocket for missions in Earth-moon space:
The U.S. military aims to get a nuclear thermal rocket up and running, to boost its ability to monitor the goings-on in Earth-moon space.
The Defense Advanced Research Projects Agency (DARPA) just awarded a $14 million task order to Gryphon Technologies, a company in Washington, D.C., that provides engineering and technical solutions to national security organizations.
The money will support DARPA's Demonstration Rocket for Agile Cislunar Operations (DRACO) program, whose main goal is to demonstrate a nuclear thermal propulsion (NTP) system in Earth orbit.
[...] NTP systems use fission reactors to heat propellants such as hydrogen to extreme temperatures, then eject the gas through nozzles to create thrust. This tech boasts a thrust-to-weight ratio about 10,000 times higher than that of electric propulsion systems and a specific impulse, or propellant efficiency, two to five times that of traditional chemical rockets, DARPA officials wrote in a description of the DRACO program.
Such improvements in propulsion technology are needed for "maintaining space domain awareness in cislunar space — the volume of space between the Earth and the moon," the DRACO description reads.
Nuclear thermal rocket on Wikipedia.
Also at Futurism.
(Score: 2) by fakefuck39 on Friday October 02 2020, @06:24PM (13 children)
yes, compressed hydrogen is energy dense for its weight, but the reactor is heavy, and the tanks to store the hydrogen are heavy. why the hell wouldn't they just use solar panels to heat the hydrogen? in addition to being lighter than uranium and the reactor, you'd have solar panels when you get there. yeah, it's about 100 times slower, but what idiot made high acceleration a requirement here? who cares if it takes 3 weeks to get to the moon or 3 months?
as a bonus, you don't have the chance of a bunch of hydrogen exploding in the atmosphere on takeoff, spreading uranium or plutonium over miles of land.
(Score: 3, Insightful) by Runaway1956 on Friday October 02 2020, @06:38PM (8 children)
Looking forward - it's a helluva lot further to Mars, than it is to the moon. There is some worry about the health effects of extended periods of space travel. Mitigating those health effects is a primary concern, correct? Then, there are the asteroids, and the further planets.
Would you rather spend 3 to 6 months traveling, or 3 years?
Speed has always been a valid concern, and it will grow ever more important as the frontiers are pushed outward.
Hail to the Nibbler in Chief.
(Score: 2) by fakefuck39 on Friday October 02 2020, @06:50PM (7 children)
It takes 9 months with current tech to get to mars. We've had a man in space for over a year and he was fine. the health effects of long stay in space is better mitigated by spinning fast, which also makes your trajectory nice and straight. the long term solution to get far is not to go faster and decelerate at the end. it's about making you be able to stay in space a long time.
(Score: 3, Informative) by PiMuNu on Friday October 02 2020, @07:04PM (4 children)
>. We've had a man in space for over a year and he was fine.
He was inside the magnetosphere, I believe.
(Score: 1, Informative) by Anonymous Coward on Friday October 02 2020, @07:18PM
Understatement of the entire thread.
The radiation exposure OUTSIDE of low earth orbit is FAR worse.
(Score: 2) by fakefuck39 on Friday October 02 2020, @07:18PM (2 children)
lol. yes, the region of space mir was in is inside part of the earth's magnetic field. the magnetic field protects against some of the radiation, but not as much as ozone and the atmosphere - that's why radiation shielding of various thickness for all spacecraft is necessary. the issue with space is lack of gravity degenerating muscle, which we solve by centripetal acceleration and working out.
you: the sky is green
me: no, the sky is blue, just look up at it
you: I just used a towel after a shower, and I believe it is now wet
(Score: 2) by Runaway1956 on Friday October 02 2020, @07:24PM (1 child)
You might want to look again.
http://strangesounds.org/wp-content/uploads/2015/05/green-sky-tornado-sign.jpg [strangesounds.org]
https://www.youtube.com/watch?v=CiDxYIT2aiI&feature=youtu.be [youtube.com]
https://strangesounds.org/2015/05/tornado-signs-sky-turns-green-during-tornado-event.html [strangesounds.org]
Sometimes, the sky is blue.
Hail to the Nibbler in Chief.
(Score: 2) by fakefuck39 on Friday October 02 2020, @10:58PM
no tornadoes here, sky still blue. but yeah, this guy clearly sees it as green, and thinks his towel being wet proves it being green. the chewbacca reasoning in the oj trials.
(Score: 0) by Anonymous Coward on Saturday October 03 2020, @05:07AM (1 child)
Spin stabilization only affects trajectory in atmosphere.
(Score: 2) by fakefuck39 on Saturday October 03 2020, @05:11PM
this is simply false. all space-bearing modules spin. while it's clear you know nothing and aren't willing to learn, you don't even have to. go watch the apollo 13 movie with tom hanks, where they spin the capsule on its way to the moon, in space.
(Score: 3, Informative) by Immerman on Saturday October 03 2020, @04:29AM (2 children)
I doubt they care about the energy density of hydrogen, they're using it as a propellant, not a fuel. Compared to the nuclear fuel accelerating it all that hydrogen energy is a tiny rounding error.
Similarly, solar energy is also basically nonexistent compared to a similar mass of nuclear fuel.
The thing is, you don't actually need a lot of mass in a nuclear reactor - you need a lot of mass in the radiation shielding. But you don't need radiation shielding in a spacecraft, because space beyond relatively low earth orbit is is already a radiation hellscape. And since it's the nuclear waste that's substantially radioactive rather than the fuel itself, you don't even need much shielding on the launching rocket to protect the ground crew - just don't start the reactor until you're in orbit. Even if fertile uranium gets blasted everywhere during launch it only presents a risk of heavy metal poisoning.
Compare that to the RTGs (a.k.a. nuclear batteries) that are already included in many space missions - where the power is actually generated from the fact that they're packed with refined radioactive waste, and if they blow up... well, there's a reason they're typically built to survive the rocket exploding.
Maybe you want some shielding between the rocket reactor and the payload of crew or sensitive equipment - but that can be a bulkhead just large enough to keep the "clean" part of the ship in its shadow. And/or a long spindly frame between the reactor and payload to use the inverse square law as your shielding - that's a popular solution in science fiction because of its practicality.
Meanwhile you want high acceleration for a few reasons -
1) if you have passengers, the radiation hellscape of space is trying very hard to kill them. Without immensely heavy shielding (at least a few meters of rock, or an equivalent mass of something else), every minute you spend in space is shortening your life expectancy, so you really want to travel as quickly as possible.
2) If you're trying to move something heavy, like a mountain of valuable metals, an asteroid refinery, or a big heavy orbital cycler "cruise ship" covered in enough rock to allow for a safe and leisurely passenger trip at roughly the minimum possible speed, you need a lot more power than chemical or solar rockets can deliver.
3) Speed is key to tactical superiority - and whoever has tactical superiority in an industrialized future in space will have strategic superiority on Earth. As well as being able to charge whatever they want to protect all those tempting mountains of valuable ores on their long slow journey to Earth.
(Score: 2) by fakefuck39 on Sunday October 04 2020, @05:28PM (1 child)
You're wrong on just about every count.
Energy density of hydrogen: nowhere did I mention "from a chemical reaction." You have a certain amount of energy - generated by solar or nuclear. You use that energy to heat an atom. On a molecular level, "heat" simply means "move faster." The energy you add to the atom is then released from the back, propelling your capsule forward. You can put that energy into a heavy atom, or you can put it into a light atom - you get the same boost in speed from either, since it's just the energy you put into the atom. Why in the hell would you want to carry heavy fuel with you instead of light fuel, since you get the same forward force out of each? The energy density here is "amount of kinetic energy forward per gram of hydrogen." So you are very wrong.
re: 1) the trip will take several months irrelevant of how fast you go. If you need shielding for several months anywise, it'll work the same for however many months you want. So you're carrying the shielding anywise - moving faster on a shorter trip buys you nothing in terms of radiation exposure.
re: 2) so your argument for "why do you need nuclear" is "you need nuclear because if you use solar you cannot move a mountain of metals in your cargo" - yeah, no one is doing that - did you even read the summary? This is a trip to the moon and mars, with some people on the ship. No one is talking about bringing asteroids into orbit.
re: 3) "we need the moon-bound capsule to go fast, because in the future we will have space wars and we need our wing fighters to go fast, because we live in a starwars episode"
you sir, are one of the dumbest fucking people on this site.
(Score: 2) by Immerman on Sunday October 04 2020, @09:46PM
>re: 1) the trip will take several months irrelevant of how fast you go.
Umm... No. Perhaps you're thinking of a Hohmann transfer orbit, which is the most efficient way to get between planets, but far from the fastest since you're reaching your destination roughly half a year after you left. You can go faster so long as you plan on slowing down at the far end instead of speeding up. It's a lot less efficient, so you wouldn't ship radiation-resistant supplies that way, but for people the difference between 8 months and 8 weeks is immense.
>This is a trip to the moon and mars, with some people on the ship
That's the plan for *this* mission - bu the government very rarely develops cutting edge technologies just for the immediate gai. In fact very often the initial mition is just an excuse to put first-generation hardware through its paces in preparation for more practical uses.
>re: 3) ... in the future we will have space wars
War is a constant ongoing state of affairs on Earth, you really think that's going to magically go away in space? Anyone who can sit in orbit and throw big rocks at the Earth is virtually guaranteed a cheap and easy victory in any conflict against an Earth-bound military. Do you really think for one minute that any space-capable government in the world is going to sit by and do nothing while a rival establishes that capability?
(Score: 2) by driverless on Sunday October 04 2020, @06:25AM
More like "why the hell don't they just dust off the more than half-century-old Project Rover [airforcemag.com]"? They've already got this done, they just never got around to using it.
(Score: 2) by Runaway1956 on Friday October 02 2020, @06:41PM (1 child)
Expect the usual suspects to line up protesting the potential contamination of virgin space. And, in the adjacent line, those protesting the weaponization of innocent space.
Hail to the Nibbler in Chief.
(Score: 2) by takyon on Friday October 02 2020, @07:38PM
$14 million? This is going to take a while.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: -1, Flamebait) by Anonymous Coward on Friday October 02 2020, @10:25PM
But it's really for Mecca. Final solution for jihadi problem
(Score: 2) by legont on Saturday October 03 2020, @01:00AM (2 children)
What does it mean, exactly? Especially in nuke terms.
"Wealth is the relentless enemy of understanding" - John Kenneth Galbraith.
(Score: 1, Informative) by Anonymous Coward on Saturday October 03 2020, @01:54PM (1 child)
This is "defense"-speak.
Replace "domain" with "battlefield".
Replace "awareness" with "threat and countermeasure preparedness".
==> Maintaining space battlefield threat and countermeasure preparedness.
It's the game we pay them to play. If ET or the Ruskies are somewhere between the earth and the moon, preparing to mount an attack, what countermeasures do we have in place to defend against it? Nuclear propulsion, once perfected, could propel countermeasures toward such a target with greater speed. In battle, speed often results in victory. Very simple, really.
(Score: 1, Insightful) by Anonymous Coward on Saturday October 03 2020, @02:24PM
It's depressing that we care more about fighting each other, rather than the common enemy of all life - entropy.
(Score: 0) by Anonymous Coward on Saturday October 03 2020, @03:49PM
uhmmm isn't there a newton law that says something like "action equals reaction"?
if "yes" then thrust gas is inert until imbuded with something, maybe with heat from unstable decaying phantom ghost matter.
once energized so, there's no prefered direction for this expanding gas.
so if you want to direct it you gotta hold one end shut.
now since decaying ghost matter is pretty energetic the "holding close one end" mechanism is gonna be pretty massive and heavy ... is it worth it?
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