There have been full scale nuclear thermal rocket engines built and tested on the ground since the 1960s. The US had the NERVA project. The attraction is that the ISP would be up to triple the ISP of chemical rockets.
Nuclear thermal propulsion (NTP) systems work by heating up a gas, usually hydrogen or ammonia, with a nuclear fission reactor and expanding that gas through a nozzle to produce efficient thrust.
All of the radiation is contained under normal operation.
NASA and the US government is again funding nuclear thermal rockets. There have been off and on nuclear thermal rockets program since the 1960s.
In 2022, DARPA announced its goal of conducting an in-space flight demonstration of nuclear thermal propulsion in 2026. In January 2023, NASA and DARPA announced a partnership to test a nuclear thermal rocket (NTR) engine in space as part of the Demonstration Rocket for Agile Cislunar Operations (DRACO) program. The goal of the DRACO project is to demonstrate revolutionary propulsion technology. This will be a smaller rocket that will only work in space. It will not take off from the ground.
ISP is a measure of fuel efficiency. Higher ISP is good because if two rockets have the same amount of fuel, then they could have thrust for longer with more fuel efficiency. This would in general mean more speed and faster travel times. However, if the rockets are not equal in fuel then a lower fuel efficiency rocket can get to the same or higher speed.
IF SpaceX has fully reusable Starships, then they could bring up loads of methane fuel and keep it in fuel depots. They could refuel rockets. They can launch a Mars rocket with multiple tanker rockets. The tanker rockets would act as another stage. The tanks would also need to fly at the same speed. They could all use up 80% of their fuel. Four tankers could then refuel the main rocket. It could be fully refueled for a final burst of speed or to decelerate from double the normal speed.
Ten or twenty launches and refuelings could be very expensive. However, if the rockets are fully reusable then it is only the incremental cost of fuel. This could be as little as $200,000 to $2 million.
Brian Wang is a Futurist Thought Leader and a popular Science blogger with 1 million readers per month. His blog Nextbigfuture.com is ranked #1 Science News Blog. It covers many disruptive technology and trends including Space, Robotics, Artificial Intelligence, Medicine, Anti-aging Biotechnology, and Nanotechnology.
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Another .. we need money to move ahead program. More public works programs AND disinformation ….
This is what should happen :
Congress to DARPA USAF – NASA – DOD and what ever ABC out fit in the budget that can’t be said in daylight .
NO MORE MONEY for any project other than current National defense . UNTIL UNTIL you come clean show us the ” UFO ” type air craft that you have . NOT A MODEL . but the ones you fly . The thesis of the propulsion system and oh yeah … ANY history on any Aliens that helped or are housed here as advisers . We want all that too. AND IF ;you come out with the data and hold anything back . In the bill will be a mandatory death sentence for any and all in the chain of custody of that information . SO how bad to you want some money …. start singing … ?
Unfortunately, Starship and space refueling will render thermal nuclear engines impractical. 5 launches of Starship for $2 million each would be $10 million. The thermal nuclear engines would have to be cheaper. I don’t see it happening. They should focus on nuclear power units which are a requirement for outer planet exploration.
Having double the specific impulse of the most efficient hydrolox engines is a huge deal. We go crazy over a 10% increase from full flow combustion cycle engines. It would be especially huge because it can produce a ton of thrust, where nuclear electric is low thrust and very very expensive fuel. Using a nuclear thermal tug between planets that stays in orbit could allow for 45 day travel times, much much higher playload to low mars orbit, or even Titan and it would require much less fuel manufacturing before returning home
They want the nuclear for speeding the Hochman transfer because humans don’t behave nicely in 8 months journeys. I believe Musk is counting on making the journey more pleasant. He has a point because speeding the spacecraft will force losing twice. Acceleration needs decceleration, too.
See more about project ROVER and Dr Raemer Schreiber’s contributions. The atomic age documentary. The Half Life of Genius. On Amazon prime and elsewhere. Never seen photos and content about the nuclear rocket engine development in the 50s and 60s.
It doesn’t have to be one or the other. Use a Falcon Heavy or Starship to bring the nuclear test bed to orbit then test out the prototype rocket. I know, that would require someone other than Elon to test iterately. Heaven forefend government contractors do this.
The best system would be a shuttle to a LEO or higher orbit, space station, then transfer to a nuclear spaceship for journeys to the Moon or Mars. Yes, chemical rockets can get to the Moon, and have, but can they do it with very large payloads and little or no refueling?
The Rube Goldberg chemical rocket to Mars and beyond scenario is just begging for trouble and failure. I’m not even convinced it could work, given that the boosters themselves need refueling, and those boosters need refueling…over and over and over…
Also, multi-week, multi-month trips require more of everything unless passengers are put into low energy hibernation, which we don’t know how to do safely yet. Then human fuel becomes like rocket fuel, in terms of volume-to-payload ratios, with diminishing returns for every extra day needed for a long journey when astronauts are basically useless until they arrive.
If this had been attempted in the ’70s or ’80s, the “nukes are the devil” crowd would have gone berserk. But I think the entire anti-nuclear movement has aged out of the population.
Yep, the world still marches forward one funeral at a time.
Nuclear thermal with solid core is not revolutionary, it was ready to fly but abandoned. USSR was slightly ahead: the RD-0410 nuclear motor was tested in non-nuclear setup and in nuclear setup. NERVA program was abandoned before producing an engine. Both would produce a flying engine, given a chance. The real revolution in nuclear propulsion was supposed to be gas core reactors, and it was in active development in USSR as of 1972. All nuclear propulsion work in USSR was stopped in 1988, likely a part of a global emotional reaction to kill all nuclear projects after Chernobyl (1986). To give the idea what revolution means, gas core propulsion is “to Jupiter and back at high thrust” kind of rocket. Testing it is only workable in space, for obvious reason: unlike solid core with hydrogen reaction mass, gas core (at five-digit Celsius temperature) slowly leaks into reaction mass. Under current conditions, the only “acceptable” nuclear rocket option would be solid core nuclear rocket, with great many constraints imposed on it – so many, that testing is more feasible on Luna. The easiest nuclear option is a nuclear-electric tug (reactor-generator plus proven plasma motors as used in satellites), but it is limited to about 1MW, compared to the 1972 project at 3.3GW, hence only for cargo due to long, long, long transit time. People go bad in so many ways during long transit time in space.
Yes, a fluid-cycle, nuclear-electric, ionic propulsion with megawatt-order power rating and low conversion efficiency (radiative heat transfer limitations) is way more reasonable than the previously abandoned NERVA rocket crap. Not to say NTP can’t be implemented a la 9M730 Burevestnik, but should the frontier of space actually open up beyond earth orbit, it isn’t going to use unserviceable, white-hot, eroding, solid fueled designs a la BWXT with cryogenic moderator/propellent. I love what the NTP fanbase calls success: “we never blew up a NERVA inverted on the stand in the desert, and ONLY lost several percent of the fuel mass to erosion during the tests at useful power density”. Any exposed oxide in the solid fuel will are destructively reduced by flow accelerated corrosion by the propellent. I guess that is fine if it will only fire for an hour over its lifespan. Often futurists fall into some unidentified logical fallacy where something is possible (NTP), so it shall be, eventually, given enough port to BWXT, NASA and enough favorable blog posts/comments.
Now, if you want to capture a kilometer-scale asteroid made of ice and put the water through a NTP rocket and nozzle, then that is slightly less realistic than space yahoos buck-Rodgersing around like Slim Pickens.
At the current point of space propulsion development curve (didn’t change much since Sputnik), every time a revolution happens, its only purpose is to make one step forward, not to become a final solution for the problem. Chemical rocket reached all Terran orbits, with a few shots further out, but even Luna is at the edge of feasibility for tonnage transfers. With a lot of brute force solutions, and even more help from electronics, BFR can do Mars, but that is pushing chemical rockets to absolute extreme in feasibility. Solid core NTP makes Mars easy, on condition that it never goes to or from Terra. It can be a first true spaceship that stays in space (orbits a destination point), it most likely can land on and lift from Luna. Paired with BFR shuttles for Terran lift, it can provide large-scale cargo transfers to Luna and Mars. That is what Musk needs for his Mars enterprise. That is all NTP has to achieve to be a feasible solution for the current space use case. Radiation is non-issue for such a use case, including core leak into exhaust plume. And I remind that it is not future tech, but an achievement from 50 years back. By the time the next step forward becomes known (inner or outer planets, high-inclination asteroids or whatever), NTP may be obsolete. High-thrust gas core at 50KK is a notion that easilytransforms into 100MK plasma fusion core – different reaction, different confinement, much better impulse, and potentially high thrust too, but still essentially a gas core. Which brings us to the last and most important point: time. Gas core, fusion core – all that will not happen in our lifetime, hence no reason to care for it. NTP can be done and be useful in our lifetime, and there is nothing else like it with high impulse and high thrust, hence there is every reason to do it at the first opportunity. Future is futurist’s domain, tech is what can be done today based on what was done yesterday.
The fuel price and extremely low thrust is an issue with nuclear electric. But with the use of argon and very large ion thrusters and acceleration over a week plus it could give 10x the ISP and the whole solar system would open up to human exploration. It’s frustrating the anti nuclear movement halted so much progress in space and in fighting climate change. I can feel change coming tho 🙂
BWXT is expected to fly what is functionally a NERVA derivative engine. DRACO is solely to bring a NERVA type engine to orbit and demonstrate it actually works there, so not that revolutionary.
Also the radioactivity isn’t contained, just sufficiently shielded to protect the payload only. Anything not covered by the shadow shield is going to have a bad day.
I’m sure he means that the exhaust doesn’t contain radioisotopes, not that the engine isn’t radiating like crazy while in operation.
You’ve got the chemical rockets, that have high thrust to weight ratios, and are good up to 380 for methane, 450 for H2.
Nerva had a specific impulse of about 850, the nuclear lightbulb was expected to have a specific impulse of 1800 or so, that’s probably as high as you’d get without nuclear fuel leakage.
A nuclear powered ion rocket could have an arbitrarily high ISP, but practically, the thrust drops off as the ISP rises, and if you can’t use all your fuel before the trip is done, what was the point of bringing it? So, say 10,000.
If leakage is acceptable the nuclear salt water rocket might reach 6-7000 seconds, and a thrust to weight ratio comparable to chemical rockets. That would actually beat the ion rocket, because you’d spend the whole trip at high speed, instead of half accelerating, and half slowing down. But you couldn’t use it to land or take off from anywhere you intended people to be.
I think the ion rocket generally beats nuclear thermal, but with nuclear thermal you can land on Mars without a second propulsion system. OTOH, since you’re already using chemical rockets to get to orbit?
Go with Starship, and a nuclear ion tug, so it arrives at Mars fully fueled. That’s what I’d do.
Not a Rockett engineer, but a ME. This seems to have merit. Much to weigh+/-, do this systematically.
Solar-Battery operated high thrust (ion) propulsion could become a thing.
CATL is at 0.5KWh/kg for commercial off the shelf at 4C discharge. A one MWh pack weighing two tons (+weight of housing) gives you 4MWh for 10 minutes. This would enable repeated medium to high thrust phases using dense storable non-cryogenic (metallic) fuels. Solar panels can recharge batteries for another round of high thrust.
There is a broad variety of acceleration mechanisms (heated/electric) that could convert this in ideal high-thrust-high-ISP. (Say ISP 2500-4000 +).
Concerning nuclear propulsion, there is a Niac grant for a bimodal high thrust nuclear space engine, using a wave rotor design. They get from 900 to 4000 ISP. Google title “New Class of Bimodal NTP/NEP with a Wave Rotor Topping Cycle Enabling Fast Transit to Mars”
“promises to deliver similar thrust as NERVA class NTP propulsion, but with Isp in the 1400-2000 second range. Coupled with an NEP cycle, the duty cycle Isp can further be increased (1800-4000 seconds) with minimal addition of dry mass. This bimodal design enables the fast transit for manned missions (45 days to Mars) and revolutionizes the deep space exploration of our solar system.”
Correction: 4MW or 6MW power and the C value is off. In media I find 4C with charging time of 10 minutes. But it should either be 6C and 10 minutes or 4C and 15minutes. Not enough information, not even on CATL website, Amperage not found.
In either case, it is good.