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NASA Looks At Reviving Atomic Rocket Program (newatlas.com)
Big Hairy Ian shares a report from New Atlas: When the first manned mission to Mars sets out, it may be on the tail of an atomic rocket engine. The Space Race vintage technology could have a renaissance at NASA after the space agency's Marshall Space Flight Center in Huntsville, Alabama signed a contract with BWXT Nuclear Energy to develop updated Nuclear Thermal Propulsion (NTP) concepts and new fuel elements to power them.
Today, with NASA once again considering the challenges of sending astronauts to Mars, the nuclear option is back on the table as part of the agency's Game Changing Development program. Under this, NASA has awarded BMXT, which supplies nuclear fuel to the U.S. Navy, a $18.8-million contract running through September 30, 2019 to look into the possibility of developing a new engine using a new type of fuel. Unlike previous designs using highly enriched uranium, BMXT will study the use of Low-Enriched Uranium (LEU), which has less than 20 percent of fissile uranium 235. This will provide a number of advantages. Not only is it safer than the highly enriched fuel, but the security arrangements are less burdensome, and the handling regulations are the same as those of a university research reactor. If NASA determines next month that the LEU engine is feasible, the project will conduct testing and refine the manufacturing process of the Cermet fuel elements over the course of a year, with testing of the full-length Cermet fuel rods to be conducted at Marshall.
Slashdot reader Big Hairy Ian adds: "At the very least it looks much more feasible than Project Orion."
Today, with NASA once again considering the challenges of sending astronauts to Mars, the nuclear option is back on the table as part of the agency's Game Changing Development program. Under this, NASA has awarded BMXT, which supplies nuclear fuel to the U.S. Navy, a $18.8-million contract running through September 30, 2019 to look into the possibility of developing a new engine using a new type of fuel. Unlike previous designs using highly enriched uranium, BMXT will study the use of Low-Enriched Uranium (LEU), which has less than 20 percent of fissile uranium 235. This will provide a number of advantages. Not only is it safer than the highly enriched fuel, but the security arrangements are less burdensome, and the handling regulations are the same as those of a university research reactor. If NASA determines next month that the LEU engine is feasible, the project will conduct testing and refine the manufacturing process of the Cermet fuel elements over the course of a year, with testing of the full-length Cermet fuel rods to be conducted at Marshall.
Slashdot reader Big Hairy Ian adds: "At the very least it looks much more feasible than Project Orion."
Nothing much. Until reactor is started for the first time, it doesn't contain anything that is not found in nature. It's basically more concentrated uranium, so it can be safely disposed of by letting it crash into the sea. And presumably, the reactor is designed in such a way that it won't become critical after immersion into seawater.
There are interesting developments in this area. For example, Kilopower ( https://en.wikipedia.org/wiki/... ) is aimed to replace RTGs since Pu-238 is becoming too scarce. It will produce about 4kW of thermal energy and will be completely passively regulated by natural thermal expansion of components - no moving parts required whatsoever.
Look at what a horrific disaster all those exploding reactors have been on navy ships and submarines!
When will people realize the horror of nuclear reactors! Radiation! Radiation!
Not to mention the ecological disaster that there would be if evil radiation were to leak in space!
Do people not realize it is the one truly pristine environment left?
Every single ONE of the radioactive RTGs that we have sent up on rockets has caused untold deaths! The chemical rockets on the other hand make rainbows brighter and butterflies more colourful!
The horror..
Come on. You can die even if you strap yourself behind a horse. You remind me of people who said (about 2 centuries ago) that going over 40 km/hours kills a human.
Speed doesn't kill
Acceleration may kill (solution, don't accelerate beyond harmful limits).
Radiation may kill (shield yourself).
Patents Drive Free Software as Hurricanes Drive Construction Industry
I'm replying as AC because I modded-up this and I think questions like this should be answered from time to time, even though I disagree with the apparent sentiments.
Firstly, "paying down the national debt" isn't necessarily as useful as one might think. Certainly, avoiding indebtedness to foreign powers may be of strategic importance, and rapid expansion of national debt for big spending programs might stoke high inflation that drives economic instability. However, most of the national debt (along with most money in the economy) is funded with money that has been created from thin-air by private-sector banks, and perhaps laundered through the economy to look more real than it is. Paying-off the original debts that created the money causes it to disappear with the debt but it provides profit in the form of interest for the banks that created the money in the first place. Very little actually goes to cover capital and interest for the deposits of any real investors, and even those originated mostly in debt to generate new assets that have been laundered and liquidated into cash for deposit. This is the world of fractional reserve banking, where almost all money in the system is born out of debt and inflation.
Now to the main point about why do this instead of "more worthwhile things we could be doing, such as curing cancer, solving world hunger, or reducing our impacts on climate change". Of course those are important and, quite rightly a good deal more money –many billions of dollars– already goes into those things than the 19 million dollars going into this project.
But blue-sky technology and pure science reap huge benefits in the long term and that simply can't be foreseen. Copernicus, Galileo, Tycho Brahe, Kepler and Newton were concerned with the motions of planetary bodies and the moon. They paved the way for the foundations of the science of mechanics which is one of the pillars of all of modern engineering and science. Franklin, Faraday and many others tinkered with electricity and magnetism, and Maxwell synthesised a theory from their experiments which gave another of pillar foundations of everything we have now. Even the highly abstract theories of Quantum Mechanics and General Relativity, formulated a century ago, now have a big impact on our everyday lives.
Everything I've described (albeit in a very brief and shallow manner) is the basis for things like MRI, CT and PET scanners, computational drug discovery, understanding climate change, GNSS/GPS and countless other technologies that have the power to benefit everyone. There are bigger political decisions to be made that will have more impact than anything gained by switching funding from atomic rockets to feeding the starving. Consider the cost of building a 2000-mile wall. And if you want another perspective, consider that, in the US alone, about $200 billion is spent each year on advertising.
Personally I have no desire to move to Mars; it's way more hostile than America would have been for early settlers, but that doesn't mean we shouldn't invest a relatively small amount. One can't imagine the long-term benefits that humanity might eventually reap from the effort.
I haven't bothered with references but if you're curious and if you really care you can easily find plenty to read about any of this.
Even SpaceX admits that for more distant missions (far outer planet destinations, oort cloud, etc), scaling chemical rockets is not sufficient. Nuclear rockets are also interesting for Venus, delivering crew and payload between the habitable layer (~54km) where breathable air is a lifting gas that can loft a colony, and orbit. Some of Venus's great advantages, like having nearly Earthlike gravity and thus no concerns about wasting like exist for the moon and (to a lesser extent) Mars, are also disadvantages, in that it's also nearly Earthlike difficulty to get to orbit. Furthermore, unlike Mars where your rocket rests on the ground, with Venus you have to support its fully fueled mass. While it's possible to get out with two-stage chemical rockets and re-dock the returning stages, you get much better mass fractions with nuclear. Even though nuclear pretty much only works with hydrogen propellant (the ISP drops in linear proportion to the atomic mass of the propellant), and hydrogen is not particularly common on Venus, the low propellant requirements mean that a nuclear rocket can use less hydrogen than most low-hydrogen rocket propellants that could be used were the ascent vehicle a two-stage chemical rocket.
I'm sure lots of people are going to be discussing NERVA in this comments section. It's important to realize that NERVA is obsolete technology, and there are much better designs available at present. NERVA's biggest problem was its awful thrust to weight ratio. One of the first realizations since then was that you can make a nuclear rocket with a LOX "afterburner"; at liftoff, you use LOX to vastly augment the thrust (the resulting ISP, while nothing like pure hydrogen nuclear-thermal, is still well above that of normal hydrolox). Once the high liftoff thrust requirements are no longer needed, the rocket transitions to pure hydrogen thrust for much higher specific impulse.
A variety of airbreathing modes have also been investigated which can strongly increase thrust and/or specific impulse further - thrust augmentation, nuclear scramjets, nuclear-driven turbojets, etc. Also, there have been general improvements in nuclear technology to allow for transferring higher energies to the hydrogen steam since then, as well as a number of yet-to-be-proven concepts. For example a fission fragment reactor can theoretically get the hydrogen much hotter than the reactor itself; in such a system, the goal is to (as much as possible) capture only neutrons in the fuel and only thermalize fission fragments (which carry most of the energy) in the hydrogen. But you definitely wouldn't pursue a fission fragment reactor with LEU....
He's really very... gentle... and fuzzy. We're becoming fast friends.
No. This sounds like a solid core nuclear rocket. Like NERVA or Dumbo. It's not that different from a plain old nuclear reactor. There's a core with the uranium rods in the middle inside an enclosed metal shell which heats the liquid hydrogen or liquid ammonia reaction mass outside that then gets ejected outwards. The only way it would leak radiation is if the metal containment failed and even then it would be a much lower level of radiation than a nuclear explosion. It would be more akin to a nuclear power plant venting over like what happened in Chernobyl.
I've heard of no plans to use these in the atmosphere. From the sounds of it they're basically planning to make a nuclear engine similar to Dumbo so that has too low a thrust-to-weight ratio to even consider using as a first stage and would only be used in upper stage application (i.e. only fired in space) to propel probes or spacecraft to far away planets.
For high-mass, Hohmann-transfer spacecrafts bound to Mars, nuclear really isn't the best propulsion option even in the long run. It's basic physics. At the low delta-Vs required for the flight, the mass ratios and volumes required are disadvantageous for nuclear, as is mined mass usage from all hydrogen sources with the exception of perhaps mining hydrogen directly from Saturn or one of the other smaller gas giants.
Ezekiel 23:20
- Tungsten Cermet Reactors presentation.
- Dumbo: A pachydermal rocket motor paper.
Fission designs have the advantage that a crew could be 'shaded' from solar flares by the heavy-isoptope fuel load. The ship's safe room would be positioned to exploit this effect.
Even SpaceX admits that for more distant missions (far outer planet destinations, oort cloud, etc), scaling chemical rockets is not sufficient.
Well, on the Falcon Heavy page they list payload to Pluto and escape velocity is only 0.39 km/s (0.03+0.02+0.11+0.20+0.03) more delta-v than that so anything inside the Sun's gravity well like the far outer planets is quite reachable by chemical. If you do ITS-style fueling in orbit or slingshot around Jupiter probably with a decent size payload too. The Oort cloud is a lot further out though, Voyager is at 139 AU and the lowest estimate for where it might begin is 2000 AU so like 500+ years even with all the gravity slingshots Voyager got. Since you won't get the same slingshot again until 2151 and the chemical propulsion is only a small part of Voyager's total speed I think you're looking at centuries even with a massive efficiency boost through fission.
Live today, because you never know what tomorrow brings
True, but even slight increases (1-2 km/s in case of Mars) cut off most of the time; afterwards, there's only diminishing returns. And we can do extra 1-2 km/s chemically just fine. Not to mention that arrival speed increases much more sharply than departure speed (and you don't want to crash into Mars at 20 km/s). However, in case of nuclear thermal propulsion, the use of asteroid-mined propellant only breaks against chemical propulsion after reaching like 10-12 km/s (that's from LEO, so about 18-20 km/s of Earth departure speed, about 47-49 km/s of heliocentric speed after leaving Earth's sphere of influence, and about 35-37 km/s in infinity). So unless you're going for the Oort cloud, it doesn't seem worth it. It's marginally better if you're lifting pure hydrogen from Earth's gravity well, but that's as unsustainable as lifting any bulk material from Earth, and the payload volume issues are still there (remember, it's only 70 kg per cubic meter for liquid hydrogen).
Ezekiel 23:20
If Humans were logical creatures we'd stop funding all military, form a planetary government, and stop all talk of Martian colonization since that's not required and diverts resources from social programs and science.
That makes sense if you look no farther than your navel, and plan for no later than next week. But on a long enough time scale, a rock is going to come along and wipe out our species, and we also develop ancillary technologies while figuring out how to explore space which pay dividends right here on Earth. Unfortunately, much of our leadership is just as short-sighted as you are.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
There are existing reactors in the hundred-kilowatt range and potential for development of megawatt range reactors, which are feasible for space - spent about 3 hours today just reading up on VASIMR and MPD engines, which - when combined with modern designs for nuclear reactors - will open up speedy access to the entire solar system, and far beyond. Check this list of reactors - old, new and potential - and the energy outputs we've already achieved: http://www.world-nuclear.org/i... The future of space exploration, is through nuclear reactors and advanced ion engines. This could have been done decades ago - the technology is more than ripe enough, to actually go ahead and do this - now.
I couldn't find any totals broken down by type of test, and I don't really want to add them all up, but about 20% of US shots were atmospheric, and it looks like most of the multi-megaton bombs were atmospheric. Quite a bit more than your 10%.
"Badly contaminated" seems similarly hyperbolic. The tests were detectable, and you didn't want to be downwind of them for sure, but except in those limited areas they don't seem to have been too catastrophic. I'm not sure why you'd say a rocket disintegrating would be worse. The most likely scenario would have a completely or mostly intact reactor falling into the ocean. The container would eventually corrode, but unenriched uranium isn't anywhere near as dangerous as the products from a working reactor or fallout from a bomb. The US military likes to shoot orders of magnitude more depleted uranium around battlefields. Also, the US SAC used to have a policy of keeping many times more weapons grade uranium and plutonium continuously airborne.
It's probably not a good idea to build a large industry that involves launching tens of thousands of reactors, but a limited number with appropriate controls wouldn't be catastrophic, particularly dangerous or even unprecedented.
Those political donations from BWX really paid off!
At first, I kinda thought you were trolling, but then there's this:
https://www.opensecrets.org/pa...
Just another day in Paradise
Airbreathing does not in any way, shape or form imply an oxygen-rich atmosphere. The most important aspect of air to a nuclear rocket is not oxygen, it's simply reaction mass.
He's really very... gentle... and fuzzy. We're becoming fast friends.