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The real lunacy is using chemical rockets instead of nuclear thermal once the ship is in orbit. That could reduce the fuel requirements for an Earth - Moon tra

The real lunacy is using chemical rockets instead of nuclear thermal once the ship is in orbit. That could reduce the fuel requirements for an Earth - Moon transfer by 4x. And this isn't some sci-fi tech. NASA built a working engine in the 70s.

buildbot 2y ago
No idea if they did or not, but one immediate issue is that if anything does go wrong, now you have a nuclear incident as well as a tragedy.
- adamomada 2y ago
  I still remember the fears of Cassini. What a different world it would be if that Earth fly-by* fucked up * edit I knew I got it wrong the first time, it’s not a transfer
  - anonymousiam 2y ago
    Lots of missions have flown RTGs, and there's always a group of protesters present every time one is launched.
jvanderbot 2y ago
International treaties and environmental protests make that infeasible.
nine_k 2y ago
But it would constitute nukes in space in a breach of international treaties! Certainly a NERVA-style rocket engine is not a nuclear bomb, and a few nuclear reactors with known and tightly watched positions won't constitute a threat of a sudden nuclear strike. But the treaties were made at times when the principal parties, the West and the Soviet bloc, did not trust each other one bit, and rightfully expected sabotage at any smallest loophole. So the treaties are overly tight. Today's world is about as bad, with a hot war in Europe, and a lot of tensions around Taiwan. No chance that the treaties would be relaxed for mutual good, due to the increased mutual trust. Breaking a treaty unilaterally just because it's inconvenient is also not great, and would untie the other sides' hands. That's why we can't have nice things. /* If you haven't yet, I recommend to read the novel Fiasco by Stanislaw Lem. It describes a civilization where all trust and cooperation are gone, and the planet is in the state of constant creeping war of sabotage. What Earthlings do there is another thing worth reading about. */
- andbberger 2y ago
  the treaty prohibits weapons, not reactors...
  - nine_k 2y ago
    Also "contamination". Despite that, NERVA has been proposed for a number of missions, mostly deeper space.
- krisoft 2y ago
  You are asserting that nuclear reactors are banned from space. Which treaty do you think does that?
marcinzm 2y ago
I would say using an engine around Earth that emits radioactive exhaust that travels at less than Earth escape velocity is the real lunacy.
qayxc 2y ago
> NASA built a working engine in the 70s. Kind of. No NTR has ever been flown and tested in space. The program achieved many milestones and got pretty far into development, but was cancelled 50 years ago due to budget constraints. It's always the last 10% that are the hardest in engineering and while NASA (as well as the Soviet Union) got 90% there, it would still have taken a few years (maybe just two) of further development. The real lunacy is simply not being mission-driven. A true mission driven design would have used a simple, reliable option using proven and existing technology. Like non-cryogenic fuel for example. Hydrazin might be highly toxic, but its beneficial chemical properties make it a much better choice for moon missions. Long term storage wouldn't be a problem and reliable proven engines already exist, too. In space (LEO and beyond), the toxicity doesn't matter while its use as a monopropellant makes it ideal for the ascend stage of a lunar lander due to reliability and simplicity. Proven technology that existed for many decades - no new engines required, no complex refuelling in orbit (just send filled tanks into LEO and keep them there for later docking), cheaper, less risk, safer...
- XorNot 2y ago
  > The real lunacy is simply not being mission-driven. Okay but why does the mission exist? People keep going "the mission is go to to the moon". Is it? Why are we doing that? How much do the "proven technologies" cost? Are they reusable? The answer of course, is that the mission is not "go to the moon". It's "go to the moon and establish permanent, long term scientific research operations with a view to using that experience to send crewed missions to Mars and other deep-space destinations". And in that box then, one might look at how the long term storage and handling of hydrazine has worked out in enclosed environments on Earth - like submarines as torpedo propellant - and concluded that the longer and more frequently you use it, the more likely you get to a vehicle loss due to the intrinsic hazards.
  - qayxc 2y ago
    > Okay but why does the mission exist? Politics. > People keep going "the mission is go to to the moon". Is it? Why are we doing that? Again, politics. The US has to assert dominance in space and cannot allow parties like China to one-up them. It's also a great way for political leadership to score points with the public. A more rational approach for establishing a permanent human presence on the moon would have included a thorough requirement analysis like Apollo did. Just FYI, SpaceX to this day (i.e. less than 12 months before the initially planned first landing!) don't even known how many tanker launches are required... > How much do the "proven technologies" cost? Less than developing a set of radically new systems from scratch - if done correctly (i.e. no cost-plus contracts). Some ideas, just for pondering: * Falcon 9 is a reliable, proven, and partly reusable system. Its capabilities are sufficient to put crew and cargo into LEO * FH is a proven and partly reusable system. Its capabilities are sufficient even for Lunar missions. * Designing a mission around these existing capabilities would eliminate the risk of developing two completely new rockets (SLS and Super Heavy/"Starship") while allowing for testing vital equipment basically from day one (i.e. autonomous docking with fuel tanks, long term fuel storage in orbit, etc.) > Are they reusable? There's no reason why a moon lander and transfer vehicles shouldn't be reusable. This is not a question of the engines or fuel used. Just a side note: the "Lunar Starship" isn't going to be reused either on its first missions. This is a medium to long term goal that hinges on quite a few factors (like the feasibility of long-term cryogenic storage in space). > one might look at how the long term storage and handling of hydrazine has worked out in enclosed environments on Earth First of all, the environments are not the same - i.e. no unprotected humans will ever be around the fuel tanks or perform hazardous activities like smoking near them or operate valves. Secondly, in stark contrast to cryogenic fuels, we actually do have plenty of data points for long term use and storage of non-cryogenic fuels in space. Most satellites used hydrazine or its derivatives for station keeping and manoeuvring in deep space missions for decades. This is nothing new whatsoever. On the other hand no one has ever successfully performed a vehicle to vehicle fuel transfer in space, let alone cryogenic fuel or long term storage of said fuels in space. This is new territory that doesn't even have all of its physics fully understood.

buildbot 2y ago

No idea if they did or not, but one immediate issue is that if anything does go wrong, now you have a nuclear incident as well as a tragedy.

adamomada 2y ago
I still remember the fears of Cassini. What a different world it would be if that Earth fly-by* fucked up * edit I knew I got it wrong the first time, it’s not a transfer
- anonymousiam 2y ago
  Lots of missions have flown RTGs, and there's always a group of protesters present every time one is launched.

jvanderbot 2y ago

International treaties and environmental protests make that infeasible.

nine_k 2y ago

But it would constitute nukes in space in a breach of international treaties! Certainly a NERVA-style rocket engine is not a nuclear bomb, and a few nuclear reactors with known and tightly watched positions won't constitute a threat of a sudden nuclear strike. But the treaties were made at times when the principal parties, the West and the Soviet bloc, did not trust each other one bit, and rightfully expected sabotage at any smallest loophole. So the treaties are overly tight. Today's world is about as bad, with a hot war in Europe, and a lot of tensions around Taiwan. No chance that the treaties would be relaxed for mutual good, due to the increased mutual trust. Breaking a treaty unilaterally just because it's inconvenient is also not great, and would untie the other sides' hands. That's why we can't have nice things. /* If you haven't yet, I recommend to read the novel Fiasco by Stanislaw Lem. It describes a civilization where all trust and cooperation are gone, and the planet is in the state of constant creeping war of sabotage. What Earthlings do there is another thing worth reading about. */

andbberger 2y ago
the treaty prohibits weapons, not reactors...
- nine_k 2y ago
  Also "contamination". Despite that, NERVA has been proposed for a number of missions, mostly deeper space.
krisoft 2y ago
You are asserting that nuclear reactors are banned from space. Which treaty do you think does that?

marcinzm 2y ago

I would say using an engine around Earth that emits radioactive exhaust that travels at less than Earth escape velocity is the real lunacy.

qayxc 2y ago

> NASA built a working engine in the 70s. Kind of. No NTR has ever been flown and tested in space. The program achieved many milestones and got pretty far into development, but was cancelled 50 years ago due to budget constraints. It's always the last 10% that are the hardest in engineering and while NASA (as well as the Soviet Union) got 90% there, it would still have taken a few years (maybe just two) of further development. The real lunacy is simply not being mission-driven. A true mission driven design would have used a simple, reliable option using proven and existing technology. Like non-cryogenic fuel for example. Hydrazin might be highly toxic, but its beneficial chemical properties make it a much better choice for moon missions. Long term storage wouldn't be a problem and reliable proven engines already exist, too. In space (LEO and beyond), the toxicity doesn't matter while its use as a monopropellant makes it ideal for the ascend stage of a lunar lander due to reliability and simplicity. Proven technology that existed for many decades - no new engines required, no complex refuelling in orbit (just send filled tanks into LEO and keep them there for later docking), cheaper, less risk, safer...

XorNot 2y ago
> The real lunacy is simply not being mission-driven. Okay but why does the mission exist? People keep going "the mission is go to to the moon". Is it? Why are we doing that? How much do the "proven technologies" cost? Are they reusable? The answer of course, is that the mission is not "go to the moon". It's "go to the moon and establish permanent, long term scientific research operations with a view to using that experience to send crewed missions to Mars and other deep-space destinations". And in that box then, one might look at how the long term storage and handling of hydrazine has worked out in enclosed environments on Earth - like submarines as torpedo propellant - and concluded that the longer and more frequently you use it, the more likely you get to a vehicle loss due to the intrinsic hazards.
- qayxc 2y ago
  > Okay but why does the mission exist? Politics. > People keep going "the mission is go to to the moon". Is it? Why are we doing that? Again, politics. The US has to assert dominance in space and cannot allow parties like China to one-up them. It's also a great way for political leadership to score points with the public. A more rational approach for establishing a permanent human presence on the moon would have included a thorough requirement analysis like Apollo did. Just FYI, SpaceX to this day (i.e. less than 12 months before the initially planned first landing!) don't even known how many tanker launches are required... > How much do the "proven technologies" cost? Less than developing a set of radically new systems from scratch - if done correctly (i.e. no cost-plus contracts). Some ideas, just for pondering: * Falcon 9 is a reliable, proven, and partly reusable system. Its capabilities are sufficient to put crew and cargo into LEO * FH is a proven and partly reusable system. Its capabilities are sufficient even for Lunar missions. * Designing a mission around these existing capabilities would eliminate the risk of developing two completely new rockets (SLS and Super Heavy/"Starship") while allowing for testing vital equipment basically from day one (i.e. autonomous docking with fuel tanks, long term fuel storage in orbit, etc.) > Are they reusable? There's no reason why a moon lander and transfer vehicles shouldn't be reusable. This is not a question of the engines or fuel used. Just a side note: the "Lunar Starship" isn't going to be reused either on its first missions. This is a medium to long term goal that hinges on quite a few factors (like the feasibility of long-term cryogenic storage in space). > one might look at how the long term storage and handling of hydrazine has worked out in enclosed environments on Earth First of all, the environments are not the same - i.e. no unprotected humans will ever be around the fuel tanks or perform hazardous activities like smoking near them or operate valves. Secondly, in stark contrast to cryogenic fuels, we actually do have plenty of data points for long term use and storage of non-cryogenic fuels in space. Most satellites used hydrazine or its derivatives for station keeping and manoeuvring in deep space missions for decades. This is nothing new whatsoever. On the other hand no one has ever successfully performed a vehicle to vehicle fuel transfer in space, let alone cryogenic fuel or long term storage of said fuels in space. This is new territory that doesn't even have all of its physics fully understood.