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Thread: Why do we not build nuclear powered space ships?

  1. #1 Why do we not build nuclear powered space ships? 
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    Not sure if this is the right sub-forum for this question, but I'm curious to know. Is it just paranoia that prevents the use of nuclear powered rockets for space travel?


    I'm not thinking like a rocket that uses small nuclear explosions to propel itself. That has some clear problems.

    I'm thinking more along the lines of a rocket that uses a very hot fuel rod to heat propellant as it is leaving the nozzle. The energy-compactness would seem to make to increase the mass-thrust ratio enough to make travel into outer space a lot easier.

    It might even be possible to use an air-breathing method to get into the upper atmosphere, and then use an on-board propellant to go the rest of the way.

    So I'm curious why this option is not being entertained? NASA rocket designers have to be aware of the possibility. Considerable research was put into creating nuclear powered aircraft in the late 1950's, and the essentials of that design would transfer with very little difficulty to a rocket design - or so I would think?


    Nuclear-powered aircraft - Wikipedia, the free encyclopedia


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    Nuclear powered aircraft can get away with "blowing" relatively large amounts of air relatively slowly.
    A rocket requires a high-speed exhaust.
    So far the only way found to do that with nuclear is to have an open-cycle system - what is heated and expelled (air or other reaction mass - caesium is one favourite IIRC) ends up irradiated.
    For some reason there's going to be a backlash of opinion about rockets spewing radioactive materials (air or not) into the atmosphere.
    Back in the 50s/ 60s there was a "cruise missile" planned.
    One aspect of it was that the exhaust trail for the entire length of its flight was about as radioactive as the explosion from its warhead.
    This didn't strike most people as a good thing in general.


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    Yes, Project Bifrost is an example of ongoing research.
    Project Bifrost - Nuclear Space Technologies | Icarus Interstellar

    Nuclear powered rockets were explored and have not been used yet, your Wikipedia page has a link included in it to a page on nuclear rocketry.
    Nuclear thermal rocket - Wikipedia, the free encyclopedia

    I don't really know why they never were accepted.
    I think it was concerns about having radioactive material falling back to earth that prevented nuclear rocket from being used for launching spacecraft but it might have been a cost issue instead.
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    nuclear powered rocket is only slightly better then chemical powered rocket in therms of fuel density. Also with nuclear technology there are risk envolved and rocket are not that safe and can explode.
    Using nuclear reactor you only produce heat and temperatures are limited to few hundred of degress C so not enough to produce plasma. You have to convert that heat into electricity using steam turbine (wery heavy machine) and then using electricity and electro magnets to produce stream of fast particles.

    Maybe you can read on Wikipedia about plasma propulsion and ion thrusters.
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    Quote Originally Posted by dan hunter View Post
    Yes, Project Bifrost is an example of ongoing research.
    Project Bifrost - Nuclear Space Technologies | Icarus Interstellar

    Nuclear powered rockets were explored and have not been used yet, your Wikipedia page has a link included in it to a page on nuclear rocketry.
    Nuclear thermal rocket - Wikipedia, the free encyclopedia

    I don't really know why they never were accepted.
    I think it was concerns about having radioactive material falling back to earth that prevented nuclear rocket from being used for launching spacecraft but it might have been a cost issue instead.
    They were working on a nuclear rocket called "NERVA" back in the late sixties, which was meant to be used for future Mars missions. However, flagging public interest in the Moon landing missions prompted congress to cut funds to NASA( at the very least, it bolstered those opponents to the program and gave them more sway), which cut the planned number of missions short and stopped production on the Saturn boosters. This left NERVA without the heavy-lifting launch platform it needed to get it into orbit. NASA ended up shifting its resources to unmanned probes and the shuttle program and the NERVA project was cancelled. things might have been different if Johnson had served another term as president. He was a huge advocate for the space program and his influence could have possibly tipped the scales the other way in congress.
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    Quote Originally Posted by svizoman View Post
    nuclear powered rocket is only slightly better then chemical powered rocket in therms of fuel density.
    Best specific impulse from chemical rockets is about 450 seconds; nuclear rockets have demonstrated specific impulses of 825 seconds.
    Also with nuclear technology there are risk envolved and rocket are not that safe and can explode.
    True - but so can chemical rockets.
    Using nuclear reactor you only produce heat and temperatures are limited to few hundred of degress C so not enough to produce plasma.
    The NERVA rockets operated at about 2000K (1700C.)
    You have to convert that heat into electricity using steam turbine (wery heavy machine) and then using electricity and electro magnets to produce stream of fast particles.
    That's something very different - a nuclear reactor powering an ion thruster. NERVA used nuclear energy directly to heat propellant. (BTW ion engines have specific impulses of up to 19,000 seconds.)
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    specific impulse is something to be bothered in solid fuel rocket. Liquid fuel rocket can operate till the fuel is gone if the nozzle cooling is sufficient. However due to staging principle if will be unwise to drag all that dead weight if you can dump it and ignite second stage.

    If chemical rocket explode you get huge fireball, on the other hand if the nuclear will explode you' will contaminate area with nuclear radiation.

    1700C is not near hot enough to produce adeqate thrust. You can produce thrust but that is only slightly better that with chemical rocket.

    You want particles being ejected at the back to travel as fast as they can (up to C). Since F=m*a you can calculate why 1700C would not produce enough pressure and thus speed. Ion particles flys up to 1/10 of C
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    Quote Originally Posted by svizoman View Post
    specific impulse is something to be bothered in solid fuel rocket.
    Specific impulse is important in ALL rockets. And I don't see where "solid fuel rocket" comes into it.

    Liquid fuel rocket can operate till the fuel is gone if the nozzle cooling is sufficient.
    And solid fuel rockets can't?

    1700C is not near hot enough to produce adeqate thrust.
    Link please.

    You can produce thrust but that is only slightly better that with chemical rocket.
    You want particles being ejected at the back to travel as fast as they can (up to C). Since F=m*a you can calculate why 1700C would not produce enough pressure and thus speed. Ion particles flys up to 1/10 of C
    Wrong. Check the Wiki page on specific impulse to learn what it means.
    Last edited by Dywyddyr; August 8th, 2017 at 09:56 AM.
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    Quote Originally Posted by svizoman View Post
    specific impulse is something to be bothered in solid fuel rocket.
    Right. Specific impulse is important to all rockets.
    Liquid fuel rocket can operate till the fuel is gone if the nozzle cooling is sufficient.
    So can solid fuel rockets.
    However due to staging principle if will be unwise to drag all that dead weight if you can dump it and ignite second stage.
    Depends on a great many things. For example, a high enough specific impulse and you don't need a second stage. The Atlas LV-3B used a single stage to get to orbit. although it dropped its outer two engines along the way.
    If chemical rocket explode you get huge fireball, on the other hand if the nuclear will explode you' will contaminate area with nuclear radiation.
    Agreed. Which is why missions that use nuclear rockets typically don't even start operation until they are close to (or in) orbit.
    1700C is not near hot enough to produce adeqate thrust. You can produce thrust but that is only slightly better that with chemical rocket.
    NERVA derivatives have specific impulses of over 900 seconds. The most efficient chemical engine out there (SSME's) are around 450 seconds. So nuclear thermal engines are more than twice as efficient as the most efficient chemical engines.
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    Quote Originally Posted by Dywyddyr View Post
    Quote Originally Posted by svizoman View Post
    specific impulse is something to be bothered in solid fuel rocket.
    Specific impulse is important in ALL rockets. And I don't see where "solid fuel rocket" comes into it.
    you are right, my bad. I thought this is actualy total impulse (force*time). Yeas you are correct specific impulse is WERY important factor.
    What I wanted to say about solid fuel rocket is that the time they burn is mostly determined by the diameter of the engine, of course there are other parameters like what king of fuel is used, etc. Solid fuel rockets have internal gutter and once ignited fuel starts to burn along the whole length of the motor. Time of burn is dependant mostly of diameter or thickness of fuel. Also this type or rocket deliver uncontroled and a bit uneven thrust so they are mostly used as a booster. Liquid fuel rockets either with turbine pumps or compressed nitrogen pumps deliver controled and smooth ride.


    Liquid fuel rocket can operate till the fuel is gone if the nozzle cooling is sufficient.
    And solid fuel rockets can't?
    They can, you are correct. Again I wanted to point out that with solid fuel rockets you don't realy have control over thrust.

    1700C is not near hot enough to produce adeqate thrust.
    Link please.

    Do not have it. Again I believe you need way higher temperatures in order to gain efficiency to a point you can say this is better that chemical rocket engine.


    You can produce thrust but that is only slightly better that with chemical rocket.
    You want particles being ejected at the back to travel as fast as they can (up to C). Since F=m*a you can calculate why 1700C would not produce enough pressure and thus speed. Ion particles flys up to 1/10 of C[/QUOTE]
    Wrong. Check the Wiki page on specific impulse to learn what it means.[/QUOTE]

    I did read on wiki, thanks for that.

    But again Newton's law still exsist and if you want to boost efficiency you need to propel matter with as much velocity as possible. In chemical rocket you both use fuel and oxidiset to give you heat and pressure and to give you mass you can accelerate thus producing thrust.

    But if we want useful engines for let's say Mars mission, we need better economy. Nuclear and chemical here is a no go.
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    Quote Originally Posted by svizoman View Post

    But if we want useful engines for let's say Mars mission, we need better economy. Nuclear and chemical here is a no go.
    The ISP of 825 sec projected for the NERVA engine was considered quite up to the needs for a Mars mission during its development. In terms of efficiency, it far out performed chemical rockets. With chemical rockets of the time a trip from LEO to Mars orbit and back to LEO would have required a fuel to payload ratio of ~36. NERVA would have reduced that ratio to ~6.4
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    Quote Originally Posted by svizoman View Post
    Also this type or rocket deliver uncontroled and a bit uneven thrust so they are mostly used as a booster. Liquid fuel rockets either with turbine pumps or compressed nitrogen pumps deliver controled and smooth ride.
    Right. But in many cases you don't care about a "smooth ride" - you care about getting to orbit. For example, the (now-cancelled) Ares I was to be a man-rated launcher; the first stage was a single solid rocket booster.
    They can, you are correct. Again I wanted to point out that with solid fuel rockets you don't realy have control over thrust.
    In cases of launchers that doesn't matter too much. As long as the final stage is throttleable, you take all the thrust you can get during liftoff.

    But if we want useful engines for let's say Mars mission, we need better economy. Nuclear and chemical here is a no go.
    Well, given that we could do a Mars mission with chemical rockets, I don't think that's true. It would definitely be easier with high thrust, high specific impulse rockets, but even regular old H2/O2 rockets will get you there (and CH4/O2 rockets will get you back.)
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    we don't have the tech yet.
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    Quote Originally Posted by 1885 View Post
    we don't have the tech yet.
    We've had the tech since the 1960's. Two NERVA engines were built and fired during that time.
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    Video inside the reactor showed the fuel elements were unstable under the vibration of the rocket. The pile shook apart. It's putting a reactor in the combustion chamber of a rocket. Any structural material to hold the fuel together interferes with the reactor by absorbing neutrons. You have to include the mass of the reactor and the propellant to compare specific impulse. That's a variable as the ratio of reactor mass to propellant mass isn't directly related. It is with chemical propellant. Then too you have to comnsider that the hotter the propellant the stronger the parts of the machine that contacts the hot material has to be. Nuclear powered electric plasma or ion drives for interstellar is a practical application.
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    Quote Originally Posted by doitright View Post
    Video inside the reactor showed the fuel elements were unstable under the vibration of the rocket. The pile shook apart.
    Nope. NERVA worked pretty well.

    There were two NERVA engines built - the Nerva NRX and the Nerva XE. Together they ran for almost four hours over almost a hundred starts, far in excess of what most missions would need. No "piles shaking apart."

    It's putting a reactor in the combustion chamber of a rocket.
    Sort of. There's no combustion going on, but that's the general idea. The nuclear pile replaces the energy that comes from combustion.

    You have to include the mass of the reactor and the propellant to compare specific impulse. That's a variable as the ratio of reactor mass to propellant mass isn't directly related. It is with chemical propellant.
    Right. But you can treat the reactor as dead weight (i.e. part of the engine) and treat the reaction mass as fuel; the classical rocket equation still works.
    Then too you have to comnsider that the hotter the propellant the stronger the parts of the machine that contacts the hot material has to be.
    Definitely. (True for all sorts of thermal rockets.)
    Nuclear powered electric plasma or ion drives for interstellar is a practical application.
    Nuclear reactors are fairly problematic in space, since dumping that much heat is not easy and requires huge radiators to get any kind of reasonable power levels.
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    Good question. Probably steam efficiency in a small space. Row row row your boat style thing. What would steam power propel? There are magnetic confined test reactors in development, but rather unstable. What could they power? Thrust?

    Ionic propulsion is much more efficient. It works in space, where it would work nowhere inside the Earths atmosphere. Low payload too.

    Solar is another low footprint space tek.
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    Quote Originally Posted by billvon View Post
    Quote Originally Posted by doitright View Post
    Video inside the reactor showed the fuel elements were unstable under the vibration of the rocket. The pile shook apart.
    Nope. NERVA worked pretty well.
    Nope. They didn't run it to destruction. Doesn't mean it produced practical impulse unless it ran to destruction. They watched video from inside the reactor showing the fuel jumping up and down in its bundles under the vibration. That showed it would have shaken apart under higher power. That's why it was terminated. .
    Quote Originally Posted by billvon View Post
    There were two NERVA engines built - the Nerva NRX and the Nerva XE. Together they ran for almost four hours over almost a hundred starts, far in excess of what most missions would need. No "piles shaking apart."
    4 hours? Of little more than a large tea kettle of hot gas. Some was hot enough to be incandescent. But nothing like rocket thrust.
    Nuclear powered electric plasma or ion drives for interstellar is a practical application.
    Quote Originally Posted by billvon View Post
    Nuclear reactors are fairly problematic in space, since dumping that much heat is not easy and requires huge radiators to get any kind of reasonable power levels.
    No it doesn't have to be an enormous reactor because the efficiency of the impulse is so high. Small reactor, little propellant mass, high impulse, long running is what make it better for space flight.
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    *citation needed*
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    Quote Originally Posted by doitright View Post
    Nope. They didn't run it to destruction. Doesn't mean it produced practical impulse unless it ran to destruction.
    So since most SpaceX Merlin engines don't run to destruction, they produce no practical impulse? A very strange claim.
    They watched video from inside the reactor showing the fuel jumping up and down in its bundles under the vibration. That showed it would have shaken apart under higher power.
    The first generation engine was run at full power for 28 of its 115 minutes of its operation. It did not "shake apart."

    The second generation engine, the XE, ran at full power for 11 minutes, and generated 55,000 lbs of thrust during that time. It did not "shake apart."

    Therefore reality contradicts your claims.

    https://ntrs.nasa.gov/archive/nasa/c...0150002614.pdf
    That's why it was terminated.
    It was terminated because the Mars mission was terminated and the anti-nuclear groups were just starting to gather steam, swinging public opinion against them.
    4 hours? Of little more than a large tea kettle of hot gas. Some was hot enough to be incandescent. But nothing like rocket thrust.
    55,000 lbs is quite a lot of thrust. It's about the same thrust as the Space Shuttle's OMS engines, the engines used to manuever the Shuttle in orbit.

    And before you scoff at 4 hours, consider that the most successful rocket engines run for far shorter times.

    F1 engine (Apollo first stage) - 2 minutes 42 seconds, then discarded
    Space Shuttle Main Engine - 8 minutes 30 seconds (best theoretical reuse - 8:30 a day for 10 days - a little over an hour firing time before major overhaul)

    The next gen NERVA design (completed before the program was cancelled) had the following specs:
    75,000 lbs thrust
    825 seconds ISP
    60 startups
    10 hour run time
    No it doesn't have to be an enormous reactor because the efficiency of the impulse is so high. Small reactor, little propellant mass, high impulse, long running is what make it better for space flight.
    High impulse equates to efficiency, not total thrust. With small reactors you still get multi-year missions due to the low thrust available and the high weight of the reactor. In fact, currently it's more feasible for inner-system exploration to use solar, because it has a higher power-to-mass ratio than available small reactors.

    You could, of course, work on lighter reactors with very advanced radiators to dissipate the heat. Indeed, the NERVA program had made some pretty big advances in small, lightweight reactors before cancellation.
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    Quote Originally Posted by billvon View Post
    55,000 lbs is quite a lot of thrust.
    You should know better. Here's where you learn better.

    To be useful in a rocket the efficiency of how the propellant is used is key. Supplied from the ground you can have any thrust you want given the energy. But how much propellant per second is used to get that thrust? Easy to get that thrust if you pump a million gallons per minute through. It was on the ground with unlimited propellant.

    The hotter it is the less propellant used for a given thrust. That's efficiency. What is called specific impulse. You mentioned that earlier. Makes me wonder whether you even understood it then. But the hotter it is the more thermal strain, the more mechanical strain by the propellant flowing through faster, and the more vibration strain by it exploding out faster.

    In your obvious ignorance I take it you've never seen, and can't find, the video from inside the reactor. You wouldn't be arguing if you had.
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    Quote Originally Posted by doitright View Post
    In your obvious ignorance I take it you've never seen, and can't find, the video from inside the reactor. You wouldn't be arguing if you had.
    And you can't be bothered to provide a link?

    Is there any particular reason for the attitude?
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    Quote Originally Posted by Dywyddyr View Post
    And you can't be bothered to provide a link?
    Not all documentaries are available on youtube.

    Quote Originally Posted by Dywyddyr View Post

    Is there any particular reason for the attitude?
    I don't like taking the time to explain something and have someone pop off with catch phrases, and irrelevant googol search results. I say he's ignorant because he ignores the facts I described of the fuel instability shown in the video he hasn't even seen, the destructive forces on the reactor literally inside a rocket engine, the limit that imposed on efficiency even at "full power" (catch phrase) My tea kettle has a "full power" setting, and the conclusion by the test teem that to compete with chemical rockets would have required a reactor construction far tougher than is possible for a nuclear reactor.

    Furthermore, ignoring the facts on structure pointed out he irrelevantly posts comparison of run times to an F1 engine with 20 times more thrust, statistics about run time, number of starts etc.

    Googol fight.
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    Quote Originally Posted by Dywyddyr View Post
    And you can't be bothered to provide a link?
    Not all documentaries are available on youtube.

    Quote Originally Posted by Dywyddyr View Post

    Is there any particular reason for the attitude?
    I don't like taking the time to explain something and have someone pop off with catch phrases, and irrelevant googol search results. I say he's ignorant because he ignores the facts I described of the fuel instability shown in the video he hasn't even seen, the destructive forces on the reactor literally inside a rocket engine, the limit that imposed on efficiency even at "full power" (catch phrase) My tea kettle has a "full power" setting, and the conclusion by the test teem that to compete with chemical rockets would have required a reactor construction far tougher than is possible for a nuclear reactor.

    Furthermore, ignoring the facts on structure pointed out he irrelevantly posts comparison of run times to an F1 engine with 20 times more thrust, statistics about run time, number of starts etc.

    Googol fight.

    Can't recognize a google fight when you see one? Or is it that you can't admit you don't understand the subject, or are not interested enough to recognize one? Since most mods don't the google fight has become the most popular cheat on boards. Still con't admit they see one even though it's well known to be the most popular cheat..
    Last edited by doitright; January 18th, 2019 at 11:10 AM.
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    Quote Originally Posted by doitright View Post
    Not all documentaries are available on youtube.
    Fine. So you could at least name the documentary.

    I don't like taking the time to explain something and have someone pop off with catch phrases, and irrelevant googol search results. I say he's ignorant because he ignores the facts I described of the fuel instability shown in the video he hasn't even seen
    I.e. a video you claim to have seen and given your interpretation of.
    Hardly a demonstrable fact.

    Put it this way: Billvon has supported his argument with checkable sources. You, on the other hand...
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    Quote Originally Posted by doitright View Post
    Quote Originally Posted by billvon View Post
    55,000 lbs is quite a lot of thrust.
    You should know better. Here's where you learn better.

    To be useful in a rocket the efficiency of how the propellant is used is key. Supplied from the ground you can have any thrust you want given the energy. But how much propellant per second is used to get that thrust? Easy to get that thrust if you pump a million gallons per minute through. It was on the ground with unlimited propellant.

    The hotter it is the less propellant used for a given thrust. That's efficiency. What is called specific impulse. You mentioned that earlier. Makes me wonder whether you even understood it then. But the hotter it is the more thermal strain, the more mechanical strain by the propellant flowing through faster, and the more vibration strain by it exploding out faster.

    In your obvious ignorance I take it you've never seen, and can't find, the video from inside the reactor. You wouldn't be arguing if you had.
    There are different ways of measuring efficiency. In terms of delta vs. reaction mass, higher exhaust velocities give better efficiencies, but in terms of thrust vs. energy, lower exhaust velocities are more efficient.
    To demonstrate, assume you have a fixed energy budget of 10J. Which would generate more thrust, a reaction mass of 10 kg at a lower velocity or a 1 kg mass at a higher velocity?

    With 10 kg you get 10J = 10v^2/2, v= 1.414 m/s, and momentum = 10(1.414)= 14.14 kgm/s
    With 1 kg, you get 10J = 1v^2/2, v= 4.47 m/s, and momentum = 1(4.47 = 4.47 kgm/s.
    For the same energy, you get less thrust from the smaller mass moving at a higher speed.
    For sure, a 10 kg reaction mass ejected 4.47 m/s provides ~3.16 time as much thrust as a the same mass ejected at 1.414 km/s, but it requires almost 10 times as much energy.

    So while rocket engines with high exhaust velocities are very efficient when it come to reaching their final speed in terms of mass ratio, they also tend to be of low thrust ( An Ion rocket that produced thrust in the range of a chemical rocket would have to have a prohibitively large energy source.

    Luckily, except for when lifting off a planetary body, thrust is not much of an issue with interplanetary travel, Long low thrust burns can be just as effective as short high thrust ones.
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    Quote Originally Posted by Dywyddyr View Post
    Quote Originally Posted by doitright View Post
    Not all documentaries are available on youtube.
    Fine. So you could at least name the documentary.

    I.e. a video you claim to have seen and given your interpretation of.
    Hardly a demonstrable fact.

    Put it this way: Billvon has supported his argument with checkable sources. You, on the other hand...
    Fine you can deny the existence of the documentary which you haven't seen, you can deny the interpretation by the makers of the documentary, and you can ignore even the possibility that it exists. Or you could spend less time watching sitcoms and watch more documentaries. Or you can assume that I gave an accurate report of the documentary and deal with that.

    But to talk in the abstract about thrust, and to assert that a naked nuclear reactor heating the propellant from inside, in effect the combustion chamber of the rocket, is, despite the insoluble problems identified by its makers, not problematic, is not an answer to the question of the OP.

    I suspect that the reason for opposition to the facts of insoluble structural problems with the nuclear rocket identified by its experimenters being what caused the program's cancellation is because there is another narrative preferred by opposers. Namely the narrative that a nuclear rocket produced too much radiation and the program was canceled because of anti nuclear sentiment.
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  29. #28  
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    Quote Originally Posted by doitright View Post
    To be useful in a rocket the efficiency of how the propellant is used is key. Supplied from the ground you can have any thrust you want given the energy. But how much propellant per second is used to get that thrust?
    That actually doesn't matter much; a large rocket that uses 100kg of propellant per second might be way more efficient than a small rocket that uses 10kg of propellant of second. What matters is something called specific impulse.

    Everything you ever wanted to know about rockets you can get from the Tsiolkovsky rocket equation:





    Commit it to memory, because it is very important. Note that the amount of delta V (velocity change, which is the most important figure of merit for any spacecraft) depends not on flow rate of propellant, but on Ve. That's the effective exhaust velocity. Or you can refer to it as specific impulse, which is Ve times g (acceleration caused by gravity.) A crude way to think of it is that specific impulse is how long a rocket can hover.

    Easy to get that thrust if you pump a million gallons per minute through. It was on the ground with unlimited propellant.
    Right. What matters is specific impulse. And nuclear rockets have a specific impulse of about twice the best chemical rockets. So you can get twice the impulse with the same fuel.

    The hotter it is the less propellant used for a given thrust. That's efficiency. What is called specific impulse.
    Exactly. You need to learn a little more about what that means.
    But the hotter it is the more thermal strain, the more mechanical strain by the propellant flowing through faster, and the more vibration strain by it exploding out faster.
    Now you are switching directions; giving up on "it's less efficient" and switching to "it's hard to do." Yes, it is. However, they did it, as proven by multiple engines running for hours without significant damage.
    In your obvious ignorance I take it you've never seen, and can't find, the video from inside the reactor. You wouldn't be arguing if you had.
    There's no video from the inside of a SpaceX Merlin engine, either. Are you going to claim that it therefore doesn't work?
    I say he's ignorant because he ignores the facts I described of the fuel instability shown in the video he hasn't even seen, the destructive forces on the reactor literally inside a rocket engine, the limit that imposed on efficiency even at "full power" (catch phrase) My tea kettle has a "full power" setting, and the conclusion by the test teem that to compete with chemical rockets would have required a reactor construction far tougher than is possible for a nuclear reactor.
    You keep claiming that. The problem is - it did work at full power. You may claim you saw a video that shows the reactor core shaking or whatever. Fine. It still survived hours of testing, far longer than most chemical engines operate.
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  30. #29  
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    Quote Originally Posted by billvon View Post
    Quote Originally Posted by doitright View Post
    I take it you've never seen, and can't find, the video from inside the reactor. You wouldn't be arguing if you had.
    There's no video from the inside of a SpaceX Merlin engine, either.
    You're confused. I said there is video from inside the reactor. You said because you haven't seen the video what I say about it isn't true.
    Quote Originally Posted by billvon View Post
    Are you going to claim that it therefore doesn't work?
    I didn't say because there is no video that therefore it doesn't work. I said because there is video it shows it doesn't work.

    Quote Originally Posted by billvon View Post
    Quote Originally Posted by doitright View Post
    to compete with chemical rockets would have required a reactor construction far tougher than is possible for a nuclear reactor.
    You keep claiming that. The problem is - it did work at full power. You may claim you saw a video that shows the reactor core shaking or whatever. Fine. It still survived hours of testing, far longer than most chemical engines operate.
    Again you keep saying "full power". There are videos on youtube show nuclear fuel expelled from the rocket. They "solved" that but don't say how in the videos. I saw the video that said they solved it by not running it at that power. They came up with a number of designs to "solve" it. They were never built because they wouldn't work either. In one of those videos on youtube they describe a design called a "nuclear light bulb". A tank of nuclear fuel heated to a gaseous state at high pressure in a tank heats the propelant flowing around the tank which is expelled at 1600 degrees. Problem with that is the same as the other. There is no material that can hold nuclear fuel at that temperature and at the pressure of a solid dense enough to sustain fission. Not to mention that even going in that direction requires a pressure vessel so heavy and thick the thickness interferes with the fission, and the weight defetes the requirement of low weight.
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