Nuclear Powered Spacecraft

Brett Davidson said:
A. Apollo Telescope Mount began its development from LM hardware.
B. Obviously. As does SR-1 and Nancy Grace Roman. Your point?
C. Some work, some fail. As with everything. You need to be more specific - what exactly do these missions have to do with my claim, what do they have in common, and which claim? That is not a refutation. Please look up the meaning of the word and explain your points more clearly.
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Nope, wrong again.
a. When Skylab went to a dry workshop, all LM hardware and design was eliminated.
From "Skylab, A Chronology". "Termination of the letter contract with Grumman, since the LM would no longer be required to house the ATM".
B Wrong, SR-1 uses the complete PPE spacecraft. RST is not a frankensat. The instrument reuses hardware and not the spacecraft.
c. Most kludge missions fail or have major problems. Skylab, Psyche, Mars Observer, and the list goes on. Anytime a spacecraft repurposes hardware there have been issues. Micrometeoroid panel on Skylab, Loral SC bus commercial construction and documentation practices led to more to a year delay while the spacecraft was at the launch site and a reduction in ion thruster efficiency, Use of LEO/GEO hardware led to Mars Observer demise.
 
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Brett Davidson said:
Have a look at the transit times and allowable masses modelled for outer planet missions, such as Tianwen-4's Uranus component - launch from Earth - proposed - 2029, Uranus flyby (no stopping), 2045.
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Irrelevant since it is not braking.
Brett Davidson said:
JIMO was cancelled because of its massive cost but considering Webb's insane overruns, all of that new technology loaded into one big spacecraft would doubtless have also come in at multiples of its already unfeasibly high cost estimates. Since NASA has studied nuclear-electric crewed missions to Mars and they've apparently pulled back from nuclear-thermal as a policy (DRACO was cancelled), then SR-1 would do a good job in developing the technology. That wouldn't be nothing.
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It doesn't really reduce the time since it has to spiral out of early orbit.
 
Scott Kenny said:
I'm still waiting for someone to propose a nuclear-ramjet atmospheric probe for the outer planets.
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The problem is that planetary scientists are just hostile to any funding of engineering projects for tomorrow when they'd rather have its funds for the also-ran craft of today.

They won't admit it of course.

Scott, my guess is that--had Falcon Heavy been a MSFC build-- you could rest assured they would have wanted to raid it's budget and flown it (instead) on a D-IV on an even more leisurely path.

We have Congress and DARPA actually eager to fund nuclear propulsion--and folks who should be happy with that would rather poor-mouth it.
 
publiusr said:
The problem is that planetary scientists are just hostile to any funding of engineering projects for tomorrow when they'd rather have its funds for the also-ran craft of today.
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Unsubstantiated statement. Show your proof.
publiusr said:
Scott, my guess is that--had Falcon Heavy been a MSFC build-- you could rest assured they would have wanted to raid it's budget and flown it (instead) on a D-IV on an even more leisurely path.
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wrong guess again.
a. MSFC would have had to raid the planetary budget just like it did for shuttle propulsion and SLS.
b. Also, there would have been no need to raid any budget if a Delta IV was used
c. Regardless, still going to be a leisurely path on Falcon heavy.

publiusr said:
We have Congress and DARPA actually eager to fund nuclear propulsion--and folks who should be happy with that would rather poor-mouth it.
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DARPA pulled its funding.
 
Brett Davidson said:
You can do better than that, in terms of both content and tone.

If you did, I'd be grateful to be informed. After all, I am only speculating.
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I was a study director on the last two planetary science decadal surveys. Go read them. You'll start to understand this better.

For example, with the last one, a goal for the Uranus orbiter and probe was to make the mission as affordable as possible while maximizing the science. No need to invent new technologies, no need to load it up with anything exotic or expensive. The attitude of the community was that they want the mission to happen as soon as possible, and a big part of that is keeping the cost as low as possible and not requiring new technologies that take time to develop.

Simply put, the planetary science community doesn't want nuclear electric propulsion for their top priority mission, the Uranus orbiter and probe.

The same applies to almost everything else you wrote in that post--the planetary science community has not stated a requirement for these things. This is a technology demonstration mission, but it will demonstrate technologies that the planetary science community has not indicated they require.

Some of this technology may be useful for other applications. Nuclear fission power could be valuable for a lunar base. But this proposal is for a micro-g application, not on the lunar surface, so it is a bit of a stretch to argue that SR-1 is directly applicable to a lunar application. Similarly, the multiple helicopters on Mars won't do much science, but they could support a human landing. A key issue for technology demonstration missions is how likely is the technology to be used by the intended user? There should be a more direct requirement and path to use.
 
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People are more willing to fund space than during Bush 41's term, however.

On a side note, the Nerd Prom disaster of last night just might have some journalists rethinking their lives, with "Orange Rocket Bad/Orange Man Bad" having played out.

I can't help but wonder if space advocates, space authors, etc....kindly old, grounded...ignored...men who quietly pushed for exploration--they might give reporters a soft place to land.

The public NEEDS grandeur....and Wonder in Man is holy.
 
blackstar said:
The same applies to almost everything else you wrote in that post--the planetary science community has not stated a requirement for these things. This is a technology demonstration mission, but it will demonstrate technologies that the planetary science community has not indicated they require.
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Thanks.

Answer to Byeman also.

blackstar said:
so it is a bit of a stretch to argue that SR-1 is directly applicable to a lunar application.
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I wasn't arguing that at all. I said that it was a likely candidate for cancellation because it was outside the Artemis ecosystem. I think you may have misunderstood me.

blackstar said:
Similarly, the multiple helicopters on Mars won't do much science, but they could support a human landing. A key issue for technology demonstration missions is how likely is the technology to be used by the intended user? There should be a more direct requirement and path to use.
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Yes, that's a key question. However, Isaacman has two major issues: avoiding the humiliation and discord with international partners over cancelling Gateway outright and squeezing a major demonstrator mission out of a declining budget. It's more political than technical and the less optimal technical solution is the only politically viable one. 'Should' is not 'can.'

I wouldn't say that the Gateway propulsion module is a complete spacecraft as it was always intended to operate as part of a system. Yes, the rest of the spacecraft will have to be designed around it, leading to undesirable compromises that wouldn't have had to be made, but a flying kluge is better than a thousand unfunded PowerPoint presentations.

It doesn't really reduce the time since it has to spiral out of early orbit.

I've seen a mission plan in which a Vasimir-propelled spacecraft slowly spirals out uncrewed and is met in high orbit by an Orion-type spacecraft carrying the crew. It's long ascending spiral spends a longer time in the Van Allen belts so leaving it uncrewed for that period is a good idea. Insertion into Mars orbit is by chemical propulsion in the reference mission linked above, using Shuttle OMS engines. The result is that the spacecraft may take a long time in total to get where it's going but the crew has as little total time exposed to radiation as possible.

So it appears to me then that nuclear-electric is suitable for ferrying crews to Mars and beyond and not necessary for cargo or scientific missions?
 
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Brett Davidson said:
I wouldn't say that the Gateway propulsion module is a complete spacecraft as it was always intended to operate as part of a system.
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But it is. Is any other space tug not a complete spacecraft?
Brett Davidson said:
I've seen a mission plan in which a Vasimir-propelled spacecraft
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Vasimir is unproven and not part of the discussion.
 
Byeman said:
But it is. Is any other space tug not a complete spacecraft?
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A tug by itself is like one telephone.

Really, this is veering into pedantry.

Byeman said:
Vasimir is unproven and not part of the discussion.
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Missing the point. Vasimir is indeed unproven but my point was that a low-thrust high-ISP spacecraft spiraling out from Earth can be met in high orbit by a crewed spacecraft using high-thrust chemical propulsion. Whether it's plasma or ion driven is irrelevant.
 
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Brett Davidson said:
Yes, that's a key question. However, Isaacman has two major issues: avoiding the humiliation and discord with international partners over cancelling Gateway outright and squeezing a major demonstrator mission out of a declining budget. It's more political than technical and the less optimal technical solution is the only politically viable one. 'Should' is not 'can.'
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I think you are misunderstanding the Skyfall mission. There are two things that motivate it:

1-Isaacman believes that nuclear electric propulsion is the space propulsion system of the future and he wants to develop it.

2-JPL does not have any work, and the helicopters and reentry vehicle will give JPL a project when otherwise it is a wasteland for them.

I am really dubious of #1 (even though I am supportive of developing fission power for lunar/Mars surface use). #2 can be accomplished without NEP. And arguably there are better projects that could be used to keep JPL afloat.
 
Brett Davidson said:
A tug by itself is like one telephone.

Really, this is veering into pedantry.
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Doesn't change the fact that Franksats have a poor success rate

Brett Davidson said:
Missing the point. Vasimir is indeed unproven but my point was that a low-thrust high-ISP spacecraft spiraling out from Earth can be met in high orbit by a crewed spacecraft using high-thrust chemical propulsion. Whether it's plasma or ion driven is irrelevant.
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yes is, because ion is still too slow. Vasimir was suppose to speed things up,
 
publiusr said:
I would like to see larger probes... multiple small cameras such that the craft doesn't have to maneuver any more than it has to.
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That makes no sense. Maneuvering is not a big deal.
 
Stern was as nervous as a long tailed cat in a room full of rocking chairs around the Pluto flyby.

That probe was tiny. If you have cameras like porcupine quills, that dish stays pointed Earthwards.
 
publiusr said:
Stern was as nervous as a long tailed cat in a room full of rocking chairs around the Pluto flyby.

That probe was tiny. If you have cameras like porcupine quills, that dish stays pointed Earthwards.
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And with what mass?
A. that still doesn't work, still requires pointing. And it is waste of mass
b. The probe is not going to send any thing during the encounter anyways, so no need for the antenna pointing.
c. Voyager had a scan platform but JPL learned some lessons and everything after Galileo like Cassini and Europa Clipper had fixed optics.
 
blackstar said:
I think you are misunderstanding the Skyfall mission. There are two things that motivate it:

1-Isaacman believes that nuclear electric propulsion is the space propulsion system of the future and he wants to develop it.

2-JPL does not have any work, and the helicopters and reentry vehicle will give JPL a project when otherwise it is a wasteland for them.

I am really dubious of #1 (even though I am supportive of developing fission power for lunar/Mars surface use). #2 can be accomplished without NEP. And arguably there are better projects that could be used to keep JPL afloat.
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Oh yes, those too.
 
Byeman said:
Doesn't change the fact that Franksats have a poor success rate
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Unfunded proposals have a zero success rate.

Byeman said:
yes is, because ion is still too slow. Vasimir was suppose to speed things up,
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So maybe plasma propulsion needs more work for a longer-term and larger scale solution.

Look, SR-1 is clearly far from ideal even as a demonstrator and it certainly isn't a prototype, but major physical components actually exist and can be used. In an ideal world, a crewed Mars transport would have a clear design and development path mapped out with guaranteed funding over the full stretch. We all know how likely that is - especially under this administration.

Therefore a lot of salvage, subterfuge, and compromise is going to be necessary. SR-1 is an opportunity to test NEP systems at medium scale over interplanetary distances. Even if it fails in its stated aims, lessons will be learned (even if they're 'don't do X'). Actual data from operating hardware beats any number of studies.

During WWII, admirals Cunningham and Kuznetsov both liked to use the quote attributed to Voltaire: 'The perfect is the enemy of the good." (Cunningham phrased it as 'Better is the enemy of good enough' while Kuznetsov said it in Russian... and Voltaire said it in French). NASA isn't at war, but like the Royal and Soviet navies, it faces huge restrictions in logistics and time.
 
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Brett Davidson said:
Look, SR-1 is clearly far from ideal even as a demonstrator and it certainly isn't a prototype, but the physical components actually exist and can be used. In an ideal world, a crewed Mars transport would have a clear design and development path mapped out with guaranteed funding over the full stretch. We all know how likely that is - especially under this administration.
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So I suspect that Elon is going to set up a trust or foundation of some kind to continue funding the Mars stuff after he passes.

Yes, I know Elon wants to go to Mars personally. Heck, I am game for the trip even if I die there. (right skill sets, training, and psychological screening, but I'd need to lose a lot of weight)

Or Elon/Trump could drop a lot of his personal funds into a trust or endowment to NASA to make sure things are paid for until delivery, with or without Congressional support.
 
Is there a way to set any kind of forum alarm to alert me if and when a human astronaut mission to Mars actually happens, nuclear powered or not...
 
Scott Kenny said:
So I suspect that Elon is going to set up a trust or foundation of some kind to continue funding the Mars stuff after he passes.
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It would be nice if he did think coherently enough long enough to do that between ketamine benders. He could do a lot of good.
 
martinbayer said:
Is there a way to set any kind of forum alarm to alert me if and when a human astronaut mission to Mars actually happens, nuclear powered or not...
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In the 19th century, there was a great fear of being buried alive (and of body snatchers like Burke and Hare digging up bodies for dissection by medical students). One solution was to have a bell hung on the grave marker with a string leading to the coffin for those who might be prematurely buried to ring. Maybe there could be an inverse of this.

Sorry, I'm not mocking you - I'm in that predicament myself!
 
Byeman said:
And with what mass?
A. that still doesn't work, still requires pointing. And it is waste of mass
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LV growth is to the point you don't have to shave every little ounce. LV shrouds aren't the prisons they once were.

I can easily see each camera mounted to its own cube sat so that when a flyby is done, the main probe is like a Pez dispenser...and beams CubeSat data back.
https://hackaday.com/2026/04/28/a-guide-to-cubesat-mission-and-bus-design/
View: https://m.youtube.com/watch?v=OCyXKRYcJ0Q&pp=0gcJCd8KAYcqIYzv


You might have maybe one or two cameras left if that, since you will essentially be handing the bus over to the heliophysics guys after you pass by Planet 9, or whatever.

If you want to risk maneuvering it around past whatever your primary target is--have at it. You will be fighting the solar dynamics guys who may not even want cameras.

A good rule of thumb is "if it can't move, it can't break." Compare Cassini's dish to Galileo...Lucy to Voyager, etc. Outer planet probes will always be expensive anyway, so make the bloody things where they would survive Omaha Beach.

Propulsion
https://phys.org/news/2026-04-nasa-powerful-lithium-fed-thruster.html

For Mars
https://arxiv.org/abs/2604.18664

https://phys.org/news/2026-04-situ-power-stations-future-mars.html
https://academic.oup.com/nsr/article/13/6/nwag043/8442246
 
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Brett Davidson said:
Unfunded proposals have a zero success rate.
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Same goes for Franksats.
But a meaningless point regardless. It doesn't justify wasting money on bad concepts.
Brett Davidson said:
Look, SR-1 is clearly far from ideal even as a demonstrator and it certainly isn't a prototype, but major physical components actually exist and can be used. In an ideal world,
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Not relevant. The only component that exists is the spacecraft bus. It like saying we have the ability to navigate and steer and the rest of the vehicle (car, truck, plane, ship, etc) is not a issue but did I happen to say it is nuclear powered.

Every comsat and spacecraft manufacturer had off the shelf designs for buses. And many have active production lines for them.

And in the long run, it might be better to treat PPE as a sunk cost and go on without it.
 
Scott Kenny said:
Or Elon/Trump could drop a lot of his personal funds into a trust or endowment to NASA to make sure things are paid for until delivery, with or without Congressional support.
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Can't give money to specific government agencies. Any money received by a US government agency goes to the general Treasury fund. Before Challenger, when the Shuttle was flying commercial spacecraft and charging for the ride, the money did not go to NASA, it went to the Treasury.
 
publiusr said:
LV growth is to the point you don't have to shave every little ounce. LV shrouds aren't the prisons they once were.
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Wrong. They will always want more propellant vs more cameras. Allows for more pointing and maneuvering.
When have LV shrouds ever been "prisons"? Answer this instead of just throwing out unsubstantiated statements and then ignoring responses to them.
publiusr said:
I can easily see each camera mounted to its own cube sat so that when a flyby is done, the main probe is like a Pez dispenser...and beams CubeSat data back.
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Space designers don't see that
a. The optics are bigger than cubesats
b. Even having six cameras covering all axis is not enough. Investigators want to point directly at the objective. Plus they would interfere with other items.
c. If the probe has passed the objective, there is nothing for the "cubesats" to do,.
publiusr said:
A good rule of thumb is "if it can't move, it can't break." Compare Cassini's dish to Galileo...Lucy to Voyager, etc. Outer planet probes will always be expensive anyway, so make the bloody things where they would survive Omaha Beach.
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They already been doing that for decades and that is why optics are now fixed to the structure. Galileo was 36 years ago.
As for Lucy, can't get around deploying solar arrays.
 
Byeman said:
And in the long run, it might be better to treat PPE as a sunk cost and go on without it.
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I think they will eventually have to do that, assuming the program does not get canceled outright. The PPE was designed to do one thing and assumed that it was getting power in a specific way. The nuclear reactor was not part of that assumption. So we can imagine that once the reactor starts coming together, it will provide power in different ways, and the PPE will have to be adapted to handle that, and adapting it means changing a lot of things, which then ripple through the entire design (in other words, it's system engineering).

I'm trying to come up with an easy analogy, but it's sorta like taking an engine built for a Ford pickup truck and fitting it into a midsize Honda sedan. Because they were not designed together, they're not going to fit together easily, or at all. We've seen that kind of problem before.
 
Byeman said:
Can't give money to specific government agencies. Any money received by a US government agency goes to the general Treasury fund. Before Challenger, when the Shuttle was flying commercial spacecraft and charging for the ride, the money did not go to NASA, it went to the Treasury.
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Endowments.

The money can literally only be spent for the purpose the endowment is established for.
 
Scott Kenny said:
Endowments.

The money can literally only be spent for the purpose the endowment is established for.
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No, Eendowments are for NGOs, non profits and universities and not for government agencies. They can't use the money as I stated.
Name one endowment that goes to a government agency.
 
Byeman said:
No, Eendowments are for NGOs, non profits and universities and not for government agencies. They can't use the money as I stated.
Name one endowment that goes to a government agency.
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Who funds the research grants? Endowments.
 
Byeman said:
Same goes for Franksats.
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Er, no. Complete failures, all of them, no data generated? Every single one of them? Are you serious? Many were flawed, but not complete failures for all. Airbus' ESM for Artemis seems to have worked pretty well despite being based on the earlier ATV. So that's an obvious misrepresentation. I'd even say disingenuous.

Byeman said:
But a meaningless point regardless. It doesn't justify wasting money on bad concepts.
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Well, I've said bad is better than nothing. Whatever. So you prefer nothing, which is what happens in the real world. Whether or not it's 'justified' in your ideal world, the question in the real world is 'can it get funded?'

As I've said, SR-1 is a candidate for cancellation because it's not clearly integral to Artemis, but i's there nonetheless, there's physical hardware and there's China.

Which do you prefer?

Byeman said:
Not relevant. The only component that exists is the spacecraft bus. It like saying we have the ability to navigate and steer and the rest of the vehicle (car, truck, plane, ship, etc) is not a issue but did I happen to say it is nuclear powered.
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Well duh. The point is to find out whether a nuclear powered system can work. How to do that? Try to do it.

Byeman said:
Every comsat and spacecraft manufacturer had off the shelf designs for buses. And many have active production lines for them.
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So OTHER Frankensats? So what is your objection? In any case, let's see them then. Let's see that they're better. Let's see them funded. Let's see buses that could be used for such a mission integrated into active, funded programmes. Name one that could demonstrate the stated aim of interplanetary NEP. What is the point you're trying to make here?

Byeman said:
And in the long run, it might be better to treat PPE as a sunk cost and go on without it.
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Go on where? Do you think NASA is entitled to funding when there are no actual missions, just endless surveys and PowerPoints of perfect missions until you wait for the Fairy Godmother to bestow funds?

Actual physical hardware, costing an estimated five billion dollars or more and ready to be used, should be thrown away in preference for some hypothetical successor that is not even in a a strategic plan, let alone a preliminary study?

Have you noticed that you have an administration determined to completely wipe out planetary science? That implied sense of entitlement is just absurd, the epitome of bureaucratic decadence.

As John Maynard Keynes said, in the long run we'll all be dead. Carpe diem.

The foundation for the future is now. You really do not seem to understand that the funding environment simply does not allow ideal development pathways. There's a point where idealism becomes posturing obstruction - if it were effective, that is.
 
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My background's in architecture, academic and professional. I've schlepped through enough professional politics (in both realms), design offices, AND building sites, to see where ideals have to give way to reality - physical, political, legal, and economic, not to mention the ever-changing and irreconcilable whims of clients. 'So tired of dealing with amateurs' someone said. Really? There's more to getting things done than devising ideal solutions for reports that end up being filed and forgotten.

Once, working for a firm working on a major civic building, I came up with the 'perfect' solution for an important detail. It turned out to uneconomic, so they chose something else. Decades later that solution is still there, real and physical; it looks OK and it does its job. I got over it long ago.
 
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Brett Davidson said:
Er, no. Complete failures, all of them, no data generated? Every single one of them? Are you serious? Many were flawed, but not complete failures for all.
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Yep all.
Brett Davidson said:
Airbus' ESM for Artemis seems to have worked pretty well despite being based on the earlier ATV. So that's an obvious misrepresentation. I'd even say disingenuous.
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Wrong, now you are changing your tune. The ESMs were not leftover ATV hardware. It is not the same as new designed based on older ones, which is done all the time and does not meet the intent of a "Frankensat". There is no unique ATV hardware in it.
Brett Davidson said:
So OTHER Frankensats?
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Nope. That is not a "Frankensat". The buses are built to order with payload unique modifications and the payload is built specifically for the bus.
 
Brett Davidson said:
My background's in architecture, academic and professional. I've schlepped through enough professional politics (in both realms), design offices, AND building sites, to see where ideals have to give way to reality - physical, political, legal, and economic, not to mention the ever-changing and irreconcilable whims of clients. 'So tired of dealing with amateurs' someone said. Really? There's more to getting things done than devising ideal solutions for reports that end up being filed and forgotten.
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My background is spacecraft launch operations and 18 of the 81 were planetary missions.
 
Brett Davidson said:
Actual physical hardware, costing an estimated five billion dollars or more and ready to be used, should be thrown away in preference for some hypothetical successor that is not even in a a strategic plan, let alone a preliminary study?
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Sunk cost fallacy. It isn't "ready" to use. It just exists. Modifying is going to cost more. Cheaper to start over.
 

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