26
votes
Accepted
Is 2001: A Space Odyssey's Discovery One still a plausible design for interplanetary travel?
Considering that the film was made before humankind first set foot on the Moon it is a fictional technological triumph and if you create something like that it should age well. And it has aged far ...
- 10.4k
17
votes
What's the typical temperature of a reactor core in a nuclear thermal rocket?
In general, the temperature is as high as they can get away with without melting, eroding, or weakening the reactor core -- this is also the motivator for unusual reactor core styles such as particle ...
- 9,517
14
votes
Accepted
Is the propulsion for the Scorpion nuclear-thermal-electric ship concept viable and credible?
As with any hypothetical design, one is limited to consider if it's making some "unreasonable" assumptions.
First, one may compare the claimed performance to existing technology. Nuclear ...
11
votes
Accepted
Are nuclear thermal engine designs limited to about twice the Isp of existing chemical rocket engines? If so, why; what's the limiting factor?
For solid core engines, yes, that's their limit.
If so, what is the limiting factor?
The exhaust velocity (and hence specific impulse) is linked to the heat of the propellant. The propellant can't ...
- 8,188
11
votes
Is 2001: A Space Odyssey's Discovery One still a plausible design for interplanetary travel?
Possibly the least plausible part of the design today is the suspended animation. While some progress has been made, long-term suspended animation of humans is still strictly science fiction.
- 189k
10
votes
Is 2001: A Space Odyssey's Discovery One still a plausible design for interplanetary travel?
Some skepticism about HAL9000 has been brought up by comments and other answers, but I think that creating a system like HAL9000 would be possible today (although it would look very different on a ...
- 21.7k
9
votes
I've heard that nuclear thermal propulsion will get 800-900 ISP. Is this the same as it got on ground tests or is it a prediction of vacuum isp?
The NERVA NRX A6 engine developed by NASA and the AEC had a specific impulse of 869sec https://en.wikipedia.org/wiki/NERVA at Jackass Flats altitude 2800ft.
Vacuum ISP can be 5%-10% higher than sea ...
- 28k
8
votes
Is it possible for Thin Film Isotope Nuclear Rockets to have an Isp over a million seconds?
I haven't been able to find anything further from this PI (James Bickford/Draper) or TFINER specifically, but broadening my search a bit to "thrust from nuclear decay" got me to A Nuclear ...
- 15.4k
7
votes
TWR of near-term NTR engines
Old, but there's an unclassifed Aerojet report RN-A-0010 for calendar year 1967 on the Space Nuclear Power 1 contract that shows these numbers
which yields thrust-to-weight around 7 with Isp's in the ...
- 189k
6
votes
Could a thermal nuclear propulsion double as a nuclear reactor?
Yes, it can.
There's also a proposed hybrid nuclear-electric system, described here, where hydrogen is run through the reactor and heated to drive a turbine to produce electricity, then run through a ...
- 172k
6
votes
Could a nuclear thermal rocket take off from the surface of the Moon?
I originally voted to close the question as I thought it was a bit broad (Can we build an NTR that can lift off from the Moon? Sure!), and because of the response to Organic Marble's and JCRM's ...
- 2,350
6
votes
Is 2001: A Space Odyssey's Discovery One still a plausible design for interplanetary travel?
A sphere is entirely the wrong shape for centrifugal gravity. In order to maximize the usable floor space, you want to have a cylindrical shape running in the same direction as the axis of rotation.
...
- 1,694
5
votes
Accepted
Alternative propellants in nuclear thermal rockets
Zinc has too high molar mass to find any practical application in Nuclear Thermal Rockets (NTR) as propellant fluid. An additional limitation in solid core NTR is the difficulty of achieving ...
- 2,341
5
votes
What is the limit on ISP for cooled physical nozzles -- and how hard is it?
The point is fairly distinct, as improved materials and designs only yield diminishing returns with respect to temperature. It's a square law, with Isp being proportional to the square root of ...
5
votes
Could a thermal nuclear propulsion double as a nuclear reactor?
To generate power from a turbine, you need a temperature gradient. Using a nuclear reactor as a heat source is straightforward enough, but you would then need to reject that heat after it has passed ...
- 2,325
4
votes
Accepted
Is "nuclear electrothermal" a recognized term for a specific technology?
Nuclear thermal propulsion and nuclear electric propulsion are distinct concepts. In nuclear thermal propulsion, a nuclear reactor is used to directly heat the propellant. The heated propellant exits ...
- 77.4k
4
votes
Are power nuclear reactors (including advanced designs) really vastly less "aggressive" in design than NTR cores?
I will argue that these reactor types are not directly comparable.
While a high "alpha" (power/mass) is desirable for both NTRs and reactors for electric power, the limiting factor that ...
4
votes
Accepted
Ultra Safe Nuclear Technologies (USNC-Tech) has delivered a design concept to NASA, but what does NASA consider a "design concept" to be?
"Design concept" sounds like it's Technology Readiness Level 2: "technology concept and/or application formulated". In short, what UNSC-Tech has delivered is a paper design for a ...
- 15.9k
3
votes
Selecting an optimal Isp / what makes an Isp too high (mostly for high Isp)
The tradeoff with specific impulse is energy: the higher the exhaust velocity (or, equivalently, the specific impulse), the more energy it requires. This is a direct consequence of the formula for ...
- 15.9k
3
votes
Selecting an optimal Isp / what makes an Isp too high (mostly for high Isp)
The concept of "optimization" typically means "given the constraints". This question isn't really answerable definitively, but the general idea to your answer would be: "The ...
- 6,300
2
votes
What are the challenges with building nuclear salt-water rockets?
Well with the design proposed by Robert Zubrin, the man to first propose this theoretical type of rocket, it is not certain that fission within current proposed nuclear saltwater rockets could easily ...
- 121
2
votes
Alternative propellants in nuclear thermal rockets
Apart from such issues, would such a propellant offer any benefits such as a high ISP, for example?
There's one and only one property that makes zinc to occasionally show up in NTR contexts.
Density
...
2
votes
With Ultra Safe Nuclear engines and hydrogen propellant, how far to Mars could you get and still be able to return to Earth in an emergency?
All the way?
This isn't really a meaningful question. If you've got sufficient delta-V to get to Mars and back, you've got sufficient delta-V to get to Mars and back. Unless you're on a continuous-...
- 15.9k
2
votes
Details about Rolls-Royce / UK Space Agency's nuclear propulsion?
The goals of the program seem to correspond to the capabilities of nuclear thermal rockets, which use nuclear fission instead of chemical energies to heat and pressurize gas that is expelled from the ...
- 1,273
2
votes
Accepted
What is the basis of the new Russian nuclear rocket propulsion?
The missile in question is a cruise missile. That means this is probably not a rocket, but a jet engine driven by a nuclear reactor. If there's any sanity left in Russia, it'll be a closed-cycle ...
- 131k
1
vote
Prior to putting spacecraft on a trajectory going a significant fraction of the speed of light, would some things need to be tested on Earth?
No.
Speed
I don't think there is anything about the speed that would need to be tested. Every time we experimentally test special or general relativity theory we get results that perfectly match. As a ...
- 151k
1
vote
Is there any way to get better performance from an NTR with non-H2 propellant?
To copy the key part of this answer (and this related earlier answer)... an important figure of merit in a rocket engine is the "characteristic velocity":
$$c_* \propto \sqrt{\frac{T_t}{M_w}}...
- 8,188
Only top scored, non community-wiki answers of a minimum length are eligible