There is a NERVA nozzle on display at the Kalamazoo Air Zoo in Michigan. It's still laced in sensor wiring. Probably mostly overlooked as it sits next to a Rocketdyne F-1!
Horses have a better mass ratio and higher thrust, but lower Isp, while mules have a worse mass ratio and low thrust, but higher Isp, so it's suitable that they tested NERVA at Jackass Flats. Not sure that counts as a tasteful joke, more like a somewhat bland observation ;)
Now this is gonna be a good series. I’m thinking, depending on where you put your shielding, one could use the spent LH2 tank as a wet workshop and the remaining nuclear reactor of the NERVA engine (albeit with some hefty radiators and other coolant systems now that the cryogenic fuel is gone) as a long term power source. Fill an intermediary tank with water or other general radiation sponges and you could (not should) be fairly safe *maybe*. I think we need to spend a couple billion dollars in cost plus contracts developing this idea.
High ISP isn't all good; there is an intrinsic (quadratic) energy inefficiency to going above the optima of about 2/3 the target delta-v, and at some point you become energy limited rather than mass limited. For LEO, chemical rockets actually aren't that far off. For nuclear, you have potentially much more energy, so might be able to trade energy inefficiency for mass efficiency, but 1) nuclear often isn't that energy dense compared to a tank of propellant if you're not willing to blow things up, and 2) the only reason to make that trade is under the assumption that mass is more expensive than energy, which I don't really buy. Credit to whoever it was that covered this on the NASASpaceFlight forums. The basic physical argument is that if all of the energy ends up in the payload, then all of the propellent should have zero velocity relative to the starting reference frame, which suggests that it should be expelled with a velocity equal to the current rocket velocity. That gives you one extreme, where you are energy optimal but infinitely mass inefficient.
Hello Eager, I have been analyzing the NERVA engine and I would like to go into detail about the exhaust of the engine, specifically its radioactivity. I have seen some official texts that state that hydrogen is not inside the reactor core for the necessary time to accumulate neutrons and become deuterium/tritium, so in general terms there are no differences between the exhaust of a chemical engine, however in your video states that it is inherently radioactive upon and after engine operation.
I don't recall seeing any data that talked about how much neutron activation you would get in hydrogen. Deuterium isn't radioactive so I wouldn't expect much of an issue there. Tritium has a short half life of 12.3 years but the radiation it produces is mostly harmless. The biggest exhaust hazard is that NERVA engines had an unfortunate tendency to melt and/or spew portions of their core out the exhaust, and those are very radioactive. There might also be issues because of the neutrons coming out the exhaust.
I read in the end of testing they found they could eliminate the drums and just throttle the turbo pumps feeding the fuel just saying !fun fact during testing a large tank of liquid hydrogen about 100,ooo gal exploded makeing a little mess of the test area fun fun fun im sure !
What do you mean by "worked"? I don't disagree that it would have generated thrust, but it's not clear that it would have been viable. The big question right now is whether NTR stages can live up to the promises made by the advocates.
Nuclear thermal made sense 40 years ago but today with massive improvements of solar panels and ion engines, nuclear does't really make much sense in inner solar system.
I would argue that nuclear thermal remains better for heavy space vehicles regardless of where you are. Ion engines have worse thrust to weight ratios, and the amount of solar panels needed to run practical ion engines for large vehicles makes that problem worse. For sufficiently light vehicles, like many satellites and maybe certain probes, ion engines seem to make sense. Heavier vehicles, especially manned ones, however, would be at a great disadvantage from the necessity of breaking up engine burns over several orbits. For unmanned vehicles, this is just an inconvenience but otherwise fine, but for a manned system the extra time in space will likely complicate the design more than it improves it. Additional consumables that could have been avoided come to mind.
Definitely a bit of an oversight. I thought about including it when I was looking at engines in general and decided not to due to lack of information and then didn't think of adding it in here.
There are a lot of places randomly called "jack-ass" around the southwest... it's too bad that kind of creativity for naming places didn't carry over to politics - so many missed opportunities!
There is a NERVA nozzle on display at the Kalamazoo Air Zoo in Michigan. It's still laced in sensor wiring.
Probably mostly overlooked as it sits next to a Rocketdyne F-1!
Horses have a better mass ratio and higher thrust, but lower Isp, while mules have a worse mass ratio and low thrust, but higher Isp, so it's suitable that they tested NERVA at Jackass Flats. Not sure that counts as a tasteful joke, more like a somewhat bland observation ;)
I'm a big fan of setting the bar appropriately...
That test was me when taco bell
Now this is gonna be a good series. I’m thinking, depending on where you put your shielding, one could use the spent LH2 tank as a wet workshop and the remaining nuclear reactor of the NERVA engine (albeit with some hefty radiators and other coolant systems now that the cryogenic fuel is gone) as a long term power source. Fill an intermediary tank with water or other general radiation sponges and you could (not should) be fairly safe *maybe*. I think we need to spend a couple billion dollars in cost plus contracts developing this idea.
There are designs for "dual mode" systems that both work as rockets and generate power.
0:52 Hey, it is the greatest toaster ever made!
Have you seen my space toast episode?
High ISP isn't all good; there is an intrinsic (quadratic) energy inefficiency to going above the optima of about 2/3 the target delta-v, and at some point you become energy limited rather than mass limited. For LEO, chemical rockets actually aren't that far off. For nuclear, you have potentially much more energy, so might be able to trade energy inefficiency for mass efficiency, but 1) nuclear often isn't that energy dense compared to a tank of propellant if you're not willing to blow things up, and 2) the only reason to make that trade is under the assumption that mass is more expensive than energy, which I don't really buy.
Credit to whoever it was that covered this on the NASASpaceFlight forums. The basic physical argument is that if all of the energy ends up in the payload, then all of the propellent should have zero velocity relative to the starting reference frame, which suggests that it should be expelled with a velocity equal to the current rocket velocity. That gives you one extreme, where you are energy optimal but infinitely mass inefficient.
Thanks.
Hello Eager, I have been analyzing the NERVA engine and I would like to go into detail about the exhaust of the engine, specifically its radioactivity. I have seen some official texts that state that hydrogen is not inside the reactor core for the necessary time to accumulate neutrons and become deuterium/tritium, so in general terms there are no differences between the exhaust of a chemical engine, however in your video states that it is inherently radioactive upon and after engine operation.
I don't recall seeing any data that talked about how much neutron activation you would get in hydrogen. Deuterium isn't radioactive so I wouldn't expect much of an issue there. Tritium has a short half life of 12.3 years but the radiation it produces is mostly harmless.
The biggest exhaust hazard is that NERVA engines had an unfortunate tendency to melt and/or spew portions of their core out the exhaust, and those are very radioactive. There might also be issues because of the neutrons coming out the exhaust.
@@EagerSpace Oh, thanks for the correction. Yes, I understand that deuterium and tritium are not radioactive, but it seemed curious to say the least.
Two great videos in s row!
Thanks. I'm hoping you like the future ones as well.
I read in the end of testing they found they could eliminate the drums and just throttle the turbo pumps feeding the fuel just saying !fun fact during testing a large tank of liquid hydrogen about 100,ooo gal exploded makeing a little mess of the test area fun fun fun im sure !
Are they trying to do this again in the near future?
Yes. New video coming out in the next few days...
To think I was a child of single digit age when this was tested. I am retired and in my 60s today. Let's get with it already!
NERVA would have worked but congress defunded it because the initiative to have a manned mission to Mars in the 1980s was summarily rejected.
What do you mean by "worked"?
I don't disagree that it would have generated thrust, but it's not clear that it would have been viable. The big question right now is whether NTR stages can live up to the promises made by the advocates.
Nuclear thermal made sense 40 years ago but today with massive improvements of solar panels and ion engines, nuclear does't really make much sense in inner solar system.
I would argue that nuclear thermal remains better for heavy space vehicles regardless of where you are. Ion engines have worse thrust to weight ratios, and the amount of solar panels needed to run practical ion engines for large vehicles makes that problem worse. For sufficiently light vehicles, like many satellites and maybe certain probes, ion engines seem to make sense. Heavier vehicles, especially manned ones, however, would be at a great disadvantage from the necessity of breaking up engine burns over several orbits. For unmanned vehicles, this is just an inconvenience but otherwise fine, but for a manned system the extra time in space will likely complicate the design more than it improves it. Additional consumables that could have been avoided come to mind.
5:00 RD-0410?
Definitely a bit of an oversight. I thought about including it when I was looking at engines in general and decided not to due to lack of information and then didn't think of adding it in here.
Why can’t I just use the nuclear reactor core as a giant toaster?
Why do you want to toast giants? What did they ever do to you?
@@EagerSpace it’s time they answered for their crimes…….
There are a lot of places randomly called "jack-ass" around the southwest... it's too bad that kind of creativity for naming places didn't carry over to politics - so many missed opportunities!