QuoteThis study takes a deep dive into the geopolitical competition for space nuclear systems for both national security and exploration, and recommends three options for in-space demonstrations before the end of the decade.Publication Linkhttps://twitter.com/LMSpace/status/1945926512777244687
This study takes a deep dive into the geopolitical competition for space nuclear systems for both national security and exploration, and recommends three options for in-space demonstrations before the end of the decade.
the insane amount of dead dry mass in that pictorial presentation
Jul 20, 2025In Nuclear Electric Propulsion, electricity is generated using a nuclear reactor and used power ion or other types of electric thrusters. Is it a practical idea, or is it another crazy nuclear rocket engine idea?Thermal Management in Space – Abraham Hertzberghttps://www.nss.org/settlement/nasa/spaceresvol2/thermalmanagement.htmlDefense systems information analysis centerhttps://dsiac.dtic.mil/articles/space-travel-aided-by-plasma-thrusters-past-present-and-future/Electric propulsion needs by OHBhttps://www.researchgate.net/publication/330082426_OHB-System's_View_on_Electric_Propulsion_NeedsVISIMR VX-200 Performance and new-term SEP capability for unmanned mars flighthttps://web.archive.org/web/20110311141639/http://spirit.as.utexas.edu/%7Efiso/telecon/Glover_1-19-11/Glover_1-19-11.pdfMegawatt class nuclear space power systems, multiple volumes:https://ntrs.nasa.gov/search?q=megawa...NASA Nuclear electric propulsion for 2033 mars roundtriphttps://www.researchgate.net/publication/237827299_Use_of_High-Power_Brayton_Nuclear_Electric_Propulsion_NEP_for_a_2033_Mars_Round-Trip_MissionNASA Compass NEP – Chemical Hybridhttps://ntrs.nasa.gov/api/citations/20210017131/downloads/TM-20210017131_errata.pdf
The use of nuclear power in space has been mixed. Many long-term spacecraft, such as the Mars rovers Curiosity and Perseverance, use radioisotope thermoelectric generators (RTGs) to provide power. Recently NASA has spoken, controversially, about placing a nuclear reactor on the moon. With regards to rockets, scientists in the 1950s explored a much more explosive possibility: driving a spacecraft forward by detonating a sequence of nuclear explosions behind it and riding the propulsive blast waves. Most notable was Project Orion, which was a concept study led by physicists Freeman Dyson and Ted Taylor and funded by the U.S. Air Force, DARPA and NASA. Then, in the 1970s, researchers associated with the British Interplanetary Society produced a comprehensive design study called Project Daedalus, which envisioned a nuclear fusion-powered engine that could reach 12% of the speed of light and reach the nearest stars in half a century.Evidently, as we're still mostly stuck on Earth, nothing ever came from these nuclear-powered design studies. Although it's not on the same scale as those overly ambitious projects, hopefully CNTR could be the breakthrough that spaceflight needs to become more routine and to reach new frontiers.A paper describing CNTR was published in the September 2025 edition of the journal Acta Astronautica.
the insane amount of dead dry mass in that pictorial presentation means someone doesn't understand the nuances of the rocket equation very well.
Space nuclear reactors have terrible power to weight, solar electric is way better until you get to the outer solar system. Nuclear electric is beyond the budget of science missions and we're nowhere close to sending humans to the outer solar system.IMO the argument for NASA doing nuclear propulsion is largely that there needs to be an use found for hardware-focused NASA centers/workforce. Which is a very real political issue, but shouldn't be confused with genuine technical benefits.
Probably not. Isaacman wants nuclear electric propulsion. DRACO was nuke thermal.An expert report by the National Research Council a few years ago argued that NASA needs to pursue both for a while and make a downselect later on based on a common set of metrics. That would be the smart thing to do.The other smart thing to do would be to set a formal ramp to get off Orion/SLS as soon as possible.
Quote from: VSECOTSPE on 11/05/2025 03:39 pmProbably not. Isaacman wants nuclear electric propulsion. DRACO was nuke thermal.An expert report by the National Research Council a few years ago argued that NASA needs to pursue both for a while and make a downselect later on based on a common set of metrics. That would be the smart thing to do.The other smart thing to do would be to set a formal ramp to get off Orion/SLS as soon as possible. Completely agree. But why choose between the 2? I've always felt that a hybrid system would serve the effort pretty well. A standard engine that could be used to power many different spacecraft; NTP for maneuvering and breaking into and out of orbit, then switch to NEP for cruise mode. Nuclear would provide electrical power constantly. I have no specific data to support this, it's simply a gut belief I harbor.
Interplanetary missions of any size require too much propellant mass, CONSTANTLY being replenished, to use chemical propulsion exclusively.
Completely agree. But why choose between the 2? I've always felt that a hybrid system would serve the effort pretty well. A standard engine that could be used to power many different spacecraft; NTP for maneuvering and breaking into and out of orbit, then switch to NEP for cruise mode. Nuclear would provide electrical power constantly. I have no specific data to support this, it's simply a gut belief I harbor. Until such time as we can safely build and operate the nuclear lightbulb, we will likely be confined to chemical propulsion to get into LEO, and that's ok. But for in-space transportation, nuclear, of some flavor, is the future, not chemical. Without it we won't be doing anything really major for a very long time. Interplanetary missions of any size require too much propellant mass, CONSTANTLY being replenished, to use chemical propulsion exclusively. Nuclear is the only efficient off-ramp from chemical. And it will take a long time of continual development to get to operational status, so the sooner we begin the effort, the better off we will be.
Until such time as we can safely build and operate the nuclear lightbulb, we will likely be confined to chemical propulsion to get into LEO, and that's ok. But for in-space transportation, nuclear, of some flavor, is the future, not chemical. Without it we won't be doing anything really major for a very long time. Interplanetary missions of any size require too much propellant mass, CONSTANTLY being replenished, to use chemical propulsion exclusively. Nuclear is the only efficient off-ramp from chemical. And it will take a long time of continual development to get to operational status, so the sooner we begin the effort, the better off we will be.
Quote from: clongton on 12/14/2025 12:54 pmCompletely agree. But why choose between the 2? I've always felt that a hybrid system would serve the effort pretty well. A standard engine that could be used to power many different spacecraft; NTP for maneuvering and breaking into and out of orbit, then switch to NEP for cruise mode. Nuclear would provide electrical power constantly. I have no specific data to support this, it's simply a gut belief I harbor. Until such time as we can safely build and operate the nuclear lightbulb, we will likely be confined to chemical propulsion to get into LEO, and that's ok. But for in-space transportation, nuclear, of some flavor, is the future, not chemical. Without it we won't be doing anything really major for a very long time. Interplanetary missions of any size require too much propellant mass, CONSTANTLY being replenished, to use chemical propulsion exclusively. Nuclear is the only efficient off-ramp from chemical. And it will take a long time of continual development to get to operational status, so the sooner we begin the effort, the better off we will be.Show me the designs for a combined NTP/NEP system, I've not seem them yet. The combined weight for separate would be hideousQuoteUntil such time as we can safely build and operate the nuclear lightbulb, we will likely be confined to chemical propulsion to get into LEO, and that's ok. But for in-space transportation, nuclear, of some flavor, is the future, not chemical. Without it we won't be doing anything really major for a very long time. Interplanetary missions of any size require too much propellant mass, CONSTANTLY being replenished, to use chemical propulsion exclusively. Nuclear is the only efficient off-ramp from chemical. And it will take a long time of continual development to get to operational status, so the sooner we begin the effort, the better off we will be.Until we have a nuclear lightbulb, chemical wins, every time. The complaint about interplanetary missions with too much propellant is simply not true, especially when you consider aerobraking giving you a free 5-10km/sec deltaV with about 15t of static mass to do so. That's less than the mass of a nuclear engine *alone*, not including it's very heavy LH2 tanks and the LH2 itself.Also consider that chemical fuel at EM-L1 point gives you enough deltaV on a standard starship to escape the solar system, it's simply not true that chemical is "too much mass" or "we won't be doing anything major".Replenishment is a well solved problem - the coal stations solved it for the British Empire in the 19th century, and the US Airforce and Navy solved it for jetA, bunker fuel, etc in the 20th century. I include both remote statiions and under-way replenishment in this. An extremely well known problem, just adapted to space travel.For Old Space, chemical is "too much mass". For new space, where we stop throwing hardware away, it's not too much mass. It's so cheap that mining fuel on remote stations like the Moon is a minor optimization.Now a lightbulb with an Isp of 2500 or more, that is probably better than chemical for all interplanetary scenarios. Good luck with that, it's a temperature of about 24,000K. for NTP (temperature is the square of the exhaust velocity).And as far as NEP, you won't get enough thrust to cut mission times at all, and you also throw away Oberth and aerobraking. It might make sense for far outer planet missions simply because the electric power will be needed beyond Jupiter for everything.
NASA Fires Up Nuclear Future for Deep Space Travelhttps://www.universetoday.com/articles/nasa-fires-up-nuclear-future-for-deep-space-travel
oh good grief, we don't need nuclear anything to go to Mars. Chemical rockets with low cost to LEO completely fill that niche, it's no contest.We need nuclear something to get to beyond the the asteroid belt. That'd be a nuclear reactor with electric propulsion most likely. I've tried my best to figure out another way, but there is no other way to travel to beyond the asteroid belt save with nuclear electric Solar is 10-20x the mass. Other tricks like electrodynamic tethers the same.
We need nuclear something to get to beyond the the asteroid belt. That'd be a nuclear reactor with electric propulsion most likely. I've tried my best to figure out another way, but there is no other way to travel to beyond the asteroid belt save with nuclear electric Solar is 10-20x the mass. Other tricks like electrodynamic tethers the same.
