Any new development on Nuclear Thermal Rocket or Orion Project?

[m4rt14n]

Is there any new development on the NTR or Nuclear Propulsion rocket engines? It seems sad that the majority of the work in the 1950s and 1960s has stalled. Even though ground tests (for NTR at least) shows a lot of potential for humankind to reach for the stars. Basically the past 40 years or so has been wasted on sub par chemical rockets that goes nowhere near the "Space Dream" that were once seems so possible.

[magnemoe]

Has been some studies on NTR however only paper projects.

Main issue with an NTR is that like in KSP you need an decent sized payload for it to make sense, that is manned missions or at least sample return.

If you only do small probes you don't need it.

Orion is much of the same story but mission size will have to be 10-100 times larger for it to make sense.

In short, 50.000 ships, warships or asteroid tugs.

However it has been some work on pulsed fusion engines who looks pretty nice, not orion class TWR more like NTR but very good isp.

[sgt_flyer]

Regarding nuclear based rockets, there 's the nuclear salt water rocket engine

http://en.m.wikipedia.org/wiki/Nuclear_salt-water_rocket (which would not require to absorb the strength of the blast like orion would)

There's also the fission fragment rocket concept

http://en.m.wikipedia.org/wiki/Fission-fragment_rocket

More specifically regarding NTRs, you have the gas core reactor rocket

http://en.m.wikipedia.org/wiki/Gas_core_reactor_rocket

Those are all concepts, but the theorics behind them would give either smoother / more efficient operations than orion or NTRs. (Besides, orion never left the drawing board too anyway )

[m4rt14n]

Payload size is largely irrelevant in comparison to goals and objectives.

Considering the farthest man made object, the Voyager I hasn't even reached the Oort Cloud yet, let alone another star system, it is clear that we as of today lack a clear objective for the space program. As in KSP, the same principle holds, stick a humongous rocket in front of a small probe and you'll get there faster.

[Nibb31]

Payload size is largely irrelevant in comparison to goals and objectives.

Considering the farthest man made object, the Voyager I hasn't even reached the Oort Cloud yet, let alone another star system, it is clear that we as of today lack a clear objective for the space program.

I don't see what Voyager has to do with our current goals and objectives. Goals have to be technologically within reach, otherwise they are meaningless. Venturing anywhere beyond our solar system is a pipe dream with any foreseeable technology, including NTRs and Orion.

As in KSP, the same principle holds, stick a humongous rocket in front of a small probe and you'll get there faster.

As a KSP player, you should know that that's not true. Getting there faster is more about timing and trajectory than about thrust.

[Red Iron Crown]

Sadly, public support in the West for anything nuclear is very soft, even if it makes a ton of sense as NTRs do.

The Russians are developing a nuclear fission reactor for spacecraft use, there is some hope for nuclear propulsion from there.

[Streetwind]

I'm pretty sure the magneto-inertial fusion rocket won't face any sort of the backlash that NTRs or nuclear-electric propulsion would face... it runs on benign fuel, performs aneutronic fusion and is run by solar panels. It's a shame that even if the project keeps running according to plan (and we know that they never do), there won't be flight hardware before 2019-2020, but it's probably one of the most realistic chances for near-term high efficiency space propulsion that has more than a featherweight for thrust. Fixed Isp of around 3000, thrust scales linearly with solar power availability. It'll probably have enough thrust to make the six-month free return ejection towards Mars, which electric engines can't do due to taking too long to accelerate and decelerate. And in contrast to chemical engines, it won't need to be refueled in-situ once there. So it could be the ideal engine for regular human travel back and forth between the two planets once the tech really gets traction.

...except, well, for the fact that it wants Helium-3 as fuel. So, uh. How's that cost effective moon mining program coming along? <__<

[Nibb31]

The trade studies for a Saturn-N planned a NERVA-derived upper stage (S-N) that would replace the S-IVB in a Saturn V stack. Although it had a significant increase in performance over the S-IVB, it wasn't a magical game changer and it had many drawbacks.

S-IVB:

Mass empty: 119,900 kg

Mass full: 223,900 kg

Propellant: LOX/LH2

Thrust (vacuum): 1,001 kN

Isp: 421 s

Burn time: 475 seconds

S-N:

Mass empty: 34000 kg

Mass full: 178000 kg

Propellants: LH2

Thrust (vacuum): 333.6 kN

Isp: 850 s

Burn Time: 1,200 seconds

As you can see, it could burn for 3 times longer, but with 1 third of the thrust, meaning that the actual increase in dV was marginal.

Edited December 1, 2014 by Nibb31

[Red Iron Crown]

As you can see, it could burn for 3 times longer, but with 1 third of the thrust, meaning that the actual increase in dV was marginal.

Does not compute. It has twice the Isp of the chemical, it should have twice the burn time with the same thrust, or six times the burn time with 1/3 the thrust if the propellant mass were the same. Something is not apples to apples with the compared specifications.

[Kryten]

The trade studies for a Saturn-N planned a NERVA-derived upper stage (S-N) that would replace the S-IVB in a Saturn V stack. Although it had a significant increase in performance over the S-IVB, it wasn't a magical game changer and it had many drawbacks.

S-IVB:

Mass empty: 119,900 kg

Mass full: 223,900 kg

Propellant: LOX/LH2

Thrust (vacuum): 1,001 kN

Isp: 421 s

Burn time: 475 seconds

S-N:

Mass empty: 34000 kg

Mass full: 178000 kg

Propellants: LH2

Thrust (vacuum): 333.6 kN

Isp: 850 s

Burn Time: 1,200 seconds

As you can see, it could burn for 3 times longer, but with 1 third of the thrust, meaning that the actual increase in dV was marginal.

Assuming payload weight of 44 tons (weight of Apollo CSM+LM stack), the delta-v from both of those is;

For S-IVB;

(ln[268,000/164,000])*(421*9.81)=2,028

2,028m/s

For S-N;

(ln[222,000/78,000])*(1,200 850*9.81)=12,313 8,646

8,646m/s.

A factor of six four seems a bit more than marginal to me.

EDIT: misread one of the burn times as I_sp; makes no major difference.

Does not compute. It has twice the Isp of the chemical, it should have twice the burn time with the same thrust, or six times the burn time with 1/3 the thrust if the propellant mass were the same. Something is not apples to apples with the compared specifications.

S-IVB has higher propellant load.

Edited December 1, 2014 by Kryten

[Nibb31]

Yeah, I pulled those figures off of Wikipedia, and looking at them now, the thrust/Isp/burn times don't make much sense.

[Red Iron Crown]

S-IVB has higher propellant load.

Something is way wrong with the Wiki specs then, the S-N has a bigger difference between empty/full masses than the S-IVB, implying the S-N has more propellant. (I would expect the S-N to have less, the NTR is likely heavier than the chemical engine.)

[m4rt14n]

Hopefully China would try on to build NTR for a manned mission to Mars.

Now if that would not move the West, I dunno what else would. Solar cells in a Nuclear engine seems a bit unnecessary...

[Streetwind]

Those are the NERVA-II rocket stage specifications. I can't find any source that confirms that this is in any way related to the Saturn C-5N concept. In fact, the stats themselves are presented on Wikipedia without any cited source, meaning there's no guarantee they're not completely made up. And well, considering the NERVA-II never left the paper concept stage, even if the original "we could probably do something similar to this" wishlist stats the scientists came up with at the time in order to try selling their project to congress were exactly like this, it doesn't mean they would have survived building an actual engine, much less an entire stage.

It might have performed worse, it might have performed better. But I'm pretty sure that whatever the performance would have turned out to be, it would have been different to what's on the wiki today. Likely significantly different.

It doesn't help that every other site you can look up info on NTRs on simply copypastes the same statblock. This might be a case of circular sourcing, where no actual original exists but enough secondary sources all cite each other to such an extent that you can't tell the difference.

Of course, if someone can dig up a reliable source on the NERVA-II (or really anything at all on that project, try finding stats for the NERVA-XE for example), then I totally want to read everything about it!

[Bill Phil]

Guys, just look at the STS NASA Proposal from 1969...

it had a good use for it

[kzauner]

Sadly, public support in the West for anything nuclear is very soft, even if it makes a ton of sense as NTRs do.

Well, this is stated frequently - and is partly true (regarding the 'soft' support). But don't forget there is currently no use-case for nuclear propulsion systems. Things may shift, if humanity needs to push 100t's interplanetary. And here I see a general problem with funding of such a mission in respect to public support. Even if I ignore the propulsion-system. In respect to the later we will probably see a VASIMR or ION-Thingy, powered by a small reactor. If you run the numbers you will see that it's not unlikely you get a better ISp out of such a construction.

[shynung]

Well, this is stated frequently - and is partly true (regarding the 'soft' support). But don't forget there is currently no use-case for nuclear propulsion systems. Things may shift, if humanity needs to push 100t's interplanetary. And here I see a general problem with funding of such a mission in respect to public support. Even if I ignore the propulsion-system. In respect to the later we will probably see a VASIMR or ION-Thingy, powered by a small reactor. If you run the numbers you will see that it's not unlikely you get a better ISp out of such a construction.

The only viable use-case for NTR in the near future is a manned Mars mission. That isn't currently popular with the public at large, which is why we're not seeing the hardware being developed.

[magnemoe]

Well, this is stated frequently - and is partly true (regarding the 'soft' support). But don't forget there is currently no use-case for nuclear propulsion systems. Things may shift, if humanity needs to push 100t's interplanetary. And here I see a general problem with funding of such a mission in respect to public support. Even if I ignore the propulsion-system. In respect to the later we will probably see a VASIMR or ION-Thingy, powered by a small reactor. If you run the numbers you will see that it's not unlikely you get a better ISp out of such a construction.

Yes, the vasmir+ reactor also has the benefit of being far easier to test. Testing an nerva so its good enough for manned flight will be an problem.

[shynung]

Yes, the vasmir+ reactor also has the benefit of being far easier to test. Testing an nerva so its good enough for manned flight will be an problem.

Why would it be a problem? Unless the reactor's propellant passages have leaks in it, nothing radioactive should come out of the exhaust; just pure hot hydrogen in gaseous form. There'd be a big flame in atmospheric conditions, but people would expect that in rocket engine tests anyway.

[Red Iron Crown]

Why would it be a problem? Unless the reactor's propellant passages have leaks in it, nothing radioactive should come out of the exhaust; just pure hot hydrogen in gaseous form. There'd be a big flame in atmospheric conditions, but people would expect that in rocket engine tests anyway.

Doesn't matter. People protest launching RTGs, all they'll hear is "nuclear rocket test" and the pitchforks will come out.

[shynung]

Ah, I see. I thought we were talking about technical problems.

^{The secret is to not let the public know either the engine tests or facts about the engine itself, the latter with more priority. How to do that, I'll leave it as an open question.}

[Kryten]

Doesn't matter. People protest launching RTGs, all they'll hear is "nuclear rocket test" and the pitchforks will come out.

People protest RTG launches, RTGs get launched. I don't see why this would be any different.

[Red Iron Crown]

People protest RTG launches, RTGs get launched. I don't see why this would be any different.

Because "nuclear rocket exhausting in delicate desert ecosystem" is going to grab more media attention than "radioactive material launched into space".

[Kryten]

Which is likely not much. We had 'dangerously radioactive material predicted to survive re-entry intact dumped over inhabited areas' as recently as '96, and there was barely a squeak from anybody.

[shynung]

Because "nuclear rocket exhausting in delicate desert ecosystem" is going to grab more media attention than "radioactive material launched into space".

They won't be able to say that if the rocket exhaust goes into a flame hood of some sort. This was used when fluorine rockets were a thing back in the 70s. NTRs are rather benign compared to these beasts.