NASA to revive the NERVA engine concept.

[Logwyn]

It's like NASA is trying to get back to the Moon by 2024 to prepare for Mars landings in the 2030s...

Should have been there already and people living on a moon station decades ago.

[Lanrefni]

Seriously? Any force in a weightless vacuum produces thrust. That’s kinda how the weightless part works.

Do remember he's a Flat Earther,so basic physics are well out of his grasp.

[Nihilist74]

This isn't even closely related to a submarine. A nuclear submarine uses radioactive material to produce electricity, the concept its the same as any other nuclear plant. Electricity can then be used to power the submarine, for example, provide electricity to the eletrical engines.

This concept o nuclear rockets is totaly diferent, as the idea is to turn energy not in electricity, but in mechanical energy, in this case thrust.

From what I understand some of the nuclear rocket engines have a reactor, the hydrogen gas is superheated by the nuclear fission reaction creating thrust. From what I have heard it is hard to control the heat from melting the whole thing down.
Could they use a nuclear reactor as an electric generator that powers a unit that superheats the hydrogen gas? Would it heat the gas up enough to create enough thrust to be worthwhile. Seems like it would be easier to control. They would also have a good source of electricity for the rest of the craft's functions.

[Masark]

This isn't even closely related to a submarine. A nuclear submarine uses radioactive material to produce electricity, the concept its the same as any other nuclear plant. Electricity can then be used to power the submarine, for example, provide electricity to the eletrical engines.

This concept o nuclear rockets is totaly diferent, as the idea is to turn energy not in electricity, but in mechanical energy, in this case thrust.

Still the same general thing, you just skip a step by throwing the superheated gas out the back rather than running it through a turbine attached to a generator.

[Hammerfest]

Because the movement of hydrogen produces thrust.

How does it do that in a vacuum?

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Newton's third law... For every action there is an equal and opposite reaction.

How does that work in a vacuum?

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The same way all rockets generate propulsion in a vacuum...

They don't.
[Infraction]

[I Push Buttons]

How does that work in a vacuum?

That was literally explained... Twice even... In the post you quoted.

Here you want a simple experiment that even you can do since you seemingly have a kindergartner's understanding of the subject? Go get a skateboard and a bowling ball... Set the skateboard on a perfectly flat smooth surface and stand on it with the bowling ball. Now throw the bowling ball forward away from yourself; you and the skateboard will roll backwards (assuming you aren't a lard ass that weighs like 300+ pounds since your inertia will be probably be high enough that you won't move).

How did that happen? Did you push off the air (which is what you childlike understanding seems to think is necessary for a rocket to work)?

No, you moved because of Newton's Third Law. The amount of force you used to throw that bowling ball was equally and oppositely applied back on yourself in the opposite direction, so you were propelled backwards with the same force that the bowling ball was propelled forward.

Rockets work the same exact way. They expel force via the rocket engine in one direction and an equal and opposite force propels them in the opposite direction. Other than atmospheric drag, which is detrimental, an atmosphere is entirely irrelevant to this process.

[Ettan]

How does it do that in a vacuum?

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How does that work in a vacuum?

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They don't.

https://www.grc.nasa.gov/WWW//K-12/airplane/rockth.html

"Notice that there is no free stream mass times free stream velocity term in the thrust equation because no external air is brought on board. Since the oxidizer is carried on board the rocket, rockets can generate thrust in a vacuum where there is no other source of oxygen. That's why a rocket will work in space, where there is no surrounding air, and a gas turbine or propeller will not work. Turbine engines and propellers rely on the atmosphere to provide air as the working fluid for propulsion and oxygen in the air as oxidizer for combustion."



Say your floating in space (in a spacesuit); throwing a wrench in any direction; you will be pushed in the opposite direction by the force you threw the wrench with. Same is true for anything, any object or particle; so even light/radiation on any wavelength.
A regular flashlight actually produces trust in space once flipped on.
That is more or less the concept of an ion drive/thruster; sending out charged particles.
(Initially very weak thrust, but these can maintain acceleration for very long, so eventually being capable of reaching very high speeds.)

[Hammerfest]

That was literally explained... Twice even... In the post you quoted.

No it wasn't. In an environment like space (or what space is supposed to be) all that this thing would produce is heat and light. Neither of which will propel anything. Newton's Third Law wouldn't apply in an environment like space, as space is understood and described. Sorry to break that to you. Space is nonsense.

[Machismo]

No it wasn't. In an environment like space (or what space is supposed to be) all that this thing would produce is heat and light. Neither of which will propel anything. Newton's Third Law wouldn't apply in an environment like space, as space is understood and described. Sorry to break that to you. Space is nonsense.

Seriously dude... stop digging yourself into this fucking hole.

[Sunseeker]

https://www.grc.nasa.gov/WWW//K-12/airplane/rockth.html

"Notice that there is no free stream mass times free stream velocity term in the thrust equation because no external air is brought on board. Since the oxidizer is carried on board the rocket, rockets can generate thrust in a vacuum where there is no other source of oxygen. That's why a rocket will work in space, where there is no surrounding air, and a gas turbine or propeller will not work. Turbine engines and propellers rely on the atmosphere to provide air as the working fluid for propulsion and oxygen in the air as oxidizer for combustion."



Say your floating in space (in a spacesuit); throwing a wrench in any direction; you will be pushed in the opposite direction by the force you threw the wrench with. Same is true for anything, any object or particle; so even light/radiation on any wavelength.
A regular flashlight actually produces trust in space once flipped on.
That is more or less the concept of an ion drive/thruster; sending out charged particles.
(Initially very weak thrust, but these can maintain acceleration for very long, so eventually being capable of reaching very high speeds.)

We really aren't kidding when we say Hammerfast is a flat-earther. Save yourself the trouble.

[s_bushido]

Stop talking to the flat-earther. The "thrust in a vacuum" thing is one of the many talking points they think is a gotcha to us silly globeheads. When they're not pouring water on soccer balls and pretending that that proves the oceans couldn't stick to the planet, of course.

[Tuor]

From what I understand some of the nuclear rocket engines have a reactor, the hydrogen gas is superheated by the nuclear fission reaction creating thrust. From what I have heard it is hard to control the heat from melting the whole thing down.
Could they use a nuclear reactor as an electric generator that powers a unit that superheats the hydrogen gas? Would it heat the gas up enough to create enough thrust to be worthwhile. Seems like it would be easier to control. They would also have a good source of electricity for the rest of the craft's functions.

Still the same general thing, you just skip a step by throwing the superheated gas out the back rather than running it through a turbine attached to a generator.

Not really, the submarines work more like a common nuclear power plant, radiactive decay warms up water, and the produced steam is pumped into a turbine. I don't know the details for this technology, but i think they might need something a little stronger then radioactive decay to warm up the hidrogen to produce thrust.

But again, i'm no expert.

[Masark]

Not really, the submarines work more like a common nuclear power plant, radiactive decay warms up water, and the produced steam is pumped into a turbine. I don't know the details for this technology, but i think they might need something a little stronger then radioactive decay to warm up the hidrogen to produce thrust.

But again, i'm no expert.

Nuclear reactors don't use radioactive decay, they uses nuclear fission.

If they used decay, that would be a radioisotope thermoelectric generator, like they use on the recent Mars rovers.

[plz delete account]

Not really, the submarines work more like a common nuclear power plant, radiactive decay warms up water, and the produced steam is pumped into a turbine. I don't know the details for this technology, but i think they might need something a little stronger then radioactive decay to warm up the hidrogen to produce thrust.

But again, i'm no expert.

Look at the video on nuclear propulsion in space I posted earlier

[Chairman Sheng-Ji Yang]

This isn't even closely related to a submarine. A nuclear submarine uses radioactive material to produce electricity, the concept its the same as any other nuclear plant. Electricity can then be used to power the submarine, for example, provide electricity to the eletrical engines.

This concept o nuclear rockets is totaly diferent, as the idea is to turn energy not in electricity, but in mechanical energy, in this case thrust.

There are different concept of nuclear propulsion in space beside the NERVA concept : an electricity-generating nuclear reactor akin to a submarine one could be used to power an ion thruster or a VASIMR.

[Tuor]

There are different concept of nuclear propulsion in space beside the NERVA concept : an electricity-generating nuclear reactor akin to a submarine one could be used to power an ion thruster or a VASIMR.

Ion Thrust, like the one used on the Dawn spacecraft can produce a stable amount of thrust for a long time, but speed its a problem because they can't speed up the spacecraft too fast. The Dawn spacecraft only used it because it had to be able to enter in orbit of low gravity bodies (Vesta and Ceres), if the spacecraft arrived there too fast the probe would had completly been unable to enter in orbit.

[Mister K]

Don't submarines use nuclear engines? Surely the same principal would apply to a spaceship for near unlimited amount of fuel? At which point it's only food/water that is the problem for longer trips.

[Shakadam]

Don't submarines use nuclear engines? Surely the same principal would apply to a spaceship for near unlimited amount of fuel? At which point it's only food/water that is the problem for longer trips.

No, not even close in fact. Anything that works in air or water can take advantage of the fact that there is a medium to "push against", i.e. using mechanical energy to move the medium (air/water) in one direction produces thrust in the opposite direction.

In vacuum and in space there's no medium to move around, so to produce any thrust you need to bring everything with you, fuel to run the engine and fuel to eject to produce thrust.

[Chairman Sheng-Ji Yang]

No, not even close in fact. Anything that works in air or water can take advantage of the fact that there is a medium to "push against", i.e. using mechanical energy to move the medium (air/water) in one direction produces thrust in the opposite direction.

In vacuum and in space there's no medium to move around, so to produce any thrust you need to bring everything with you, fuel to run the engine and fuel to eject to produce thrust.

To sum it up, to move you need a source of energy and a reaction mass :
-in conventional rockets the fuel double down as both
-similarly with Project Orion or Project Daedalus the fuel (atomic bombs/He3 pellets) is both source of energy and reaction mass
-in nuclear thermal, nuclear electric, electric and ablative laser propulsion the energy source is different from the reaction mass.

But there is an exception in solar sails, which are moved by the sun or by a laser without requiring reaction mass.

[Jonnusthegreat]

Just build a damn space ladder already. If we don't we are going to deplete all our resources going to space. Megastructures ftw!