Nuclear rocket engines | Lex Fridman Podcast Clips 

Full podcast episode: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-5eK5A_43pkE.html Lex Fridman podcast channel: ru-vid.com Guest bio: Tim Dodd is host of the Everyday Astronaut RU-vid channel, where he teaches about rocket engines and all things space travel.

My friend, now deceased, Al Poindexter was a dedicated engineer on project NERVA. He told me about how he was so dedicated to the mission that he stayed with engine from the moment it was loaded on to a train car at Westinghouse Astro Nuclear until it arrived at Jackass Flats and then throughout it's testing. Literally he stayed on the train car with it! He also told me that the engine was protected and packed off to Hanford, Wa where it sits and was still in operating condition at that time..

"The Mars mission became NERVA's downfall. Members of Congress in both political parties judged that a manned mission to Mars would be a tacit commitment for the United States to decades more of the expensive Space Race. Manned Mars missions were enabled by nuclear rockets; therefore, if NERVA could be discontinued the Space Race might wind down and the budget would be saved."

Hey this was all great. Do another interview with this chap.

This is an exciting topic to me because I remember reading about Project Orion in Omni Magazine in 198...6? It seemed so cool to lil me. Thank you for the amazing covo!

Pulsed nuclear thermal is an interesting expansion of regular nuclear thermal engines. Using pulsed reaction (inserting/removing control rods) heats up propelant to higher temperatures giving higher specific impulse.

Nuclear Pulse also known as Project Orion. It is a pretty cool concept.

I often think about if the moon were rich in some scarce resource, would we be way further advanced in our space travel capabilities? It’s such a shame that we really haven’t progressed a timer further from the 60s.

bien joué, Bravo LEX

I love you guys. Tim misspoke, the reactor is fission, not fusion (high mass nucleons decaying, not light mass fusing). I am sure it was just a misspeak. I have always said nucular, not nuclear, power. built a few in my career.

Other than the obvious weight problem, hydrogen is not easy to deal with. It is difficult to build tanks to hold it in, as the tanks will usually leak because hydrogen molecules are very small. Plus, the tanks become very heavy and nitrogen doesn't have / give a good amount of thrust. I believe hydrogen should be off the table for use until we can find a lighter weight tank solution.

lex has been watching PBS space time

Sometimes 'guessing about things we don't know about', is the best way to come up with new ideas, new thoughts! Your truly thinking outside the box!

The late Stanton Friedman was developing these 50 yrs ago. We have technologies far in advance of rockets. Ben Rich head of the top secret Lockheed Martin Skunk Works admitted at a conference that we have the means to take E.T. home.

You guys missed talking about rotating detonation engines.

But that said, strapping a thousand birds to your head would work.

Nuclear thermal is basically still the same temperature as chemical rockets because we're limited by materials properties. The only real benefit you're getting is the ejecta are Hydrogen which are 9-18 times lighter than water at the same temperature (and accordingly 3-4 times higher Isp)

Why not flying ? Because in 1996 NASA dropped a plutonium core in the atmosphere and pretty much covered it up.

IMHO a good reason to not go for nuclear rocket engines is that, even if it's just payload and thus not used for take off itself, but only to be started way out of earth's way, you don't want to risk to spread radioactive material over earths surface in case the rocket blows up during take off.

"it'd be stupid for us to guess about things we dont even know about yet." isnt that literally how science works.

Do not strap a thousand birds to your head 🚨

Steam rockets, how Punk!

Its a real shame the Sea Dragon never came to pass, western leaders didn't want anything to do with the pursuit of space travel so it was a shelved design. It would have been amazing to see take off.

They have it, its been around since around the 50s and it works. But its solely for space travel because of its safety regulations. Goes roughly 3/10 the speed of light.

LoL, initially, I thought that you believed that nuclear or fusion drives could allow us to go study black holes. Anyhow, I really hope one day we'd unlock tech that nowadays is unbelievable. Yet we're at a point in history that requires bright or even superhuman minds. Like thinking about 8 or 11 dimentions. To my understanding, both machine learning and physics make use of those for one reason or another.

Just one sort of Thrust/Shockwave propulsion that could be tested in the next few 100 years to see whether it makes any sense to use it, could be something that uses energy from focusing solar energy transmitted by solar panel satellites on space. The energy from several transmitting satellites is focused (some groups like one at Caltech are already working on Solar Power on orbit) onto a LASER on the rocket (modulo taking care of all the precise control of several beams following the rocket motion). If the energy is going to come from outside, energy density is perhaps not a big problem (although energy carrying/handling capacity would be), so might as choose the propellant independent of the energy density. As mentioned in the video, something (propellant) still needs to be ejected until we can control spacetime or quantum fields at scale, and the propellant needs to be stored on the rocket unless it can be harvested during the motion which is rather difficult with the thinning of the atmosphere with increasing altitude. So, let's say compressed air is used as a propellant. The LASER ionizes the air at the exit of the tank, and the ion jet is accelerated with magnetic field on board the rocket. It is likely that some forward boost/shockwave phenomenon could be studied based on certain kinds of elastic behavior of the magnetic field. If solar power could be harvested from space in reasonable quantities, it could potentially be used to power rockets.

3 mile island put nuclear propulsion on the back burner in the US. I remember all the public outrage when the first nuclear satellite was launched

1 pulse. Zero resistance.....???

Wouldn’t the exhaust bombard earth when leaving and arriving

Why not just build it in space from pieces?

99% of us are just peasants in physics land. Well I'm in good company!

Thrust is about reaction to momentum of the exhaust so hydrogen being the lightest element is rather lousy.

Element 115 bois

I think is all going to be about harnissing vast amounts of energy. Energy seems to be the one constant in all models. Essentially all mass is energy as per relativity, and as mass seems to derive gravitational potential, potentially so does energy. In theory you can bend space-time enough to travel at or over faster than light.... only problem is you need silly amounts of energy, like more than available in our galaxy, to bend space enough to move just a few kg. Hopefully one day someone will break this curernt understanding of physics wide open👍

He wears a T-Shirt of Elon's Holy Grail.

Aliens got around it .. by using Mercury electromagnetic drive energy to use a field to push themselves beyond light speed

nuclear rocket engines ok but with people is that not a problem with weight of shielding ?

Evian BUssin.

Clearly we're not fully there design wise 4 us 2 fully understand this 1 has to look at poo In layman terminology cow crap when heated by the sun shoots tiny pieces of shit to the atmosphere quicker and ultimately faster than anything else on earth So imagine the rocket is the tiny piece of shit , we're missing the turd This is not a joke

For the question at 4:20: E L E M E N T 1 1 5

I thought dark energy was up to like 95% of our universe and we can barely see it, we have nothing if that's stuff plays a big rolein an anything, pessimism at its finest 🖖 but it's true how much can we really see we can barely catch individual pieces of dark energy and if that's 95% it'll tear everything we know to shreds in an instant when we're smarterer some day if we make it that far knock on wood

2nd

Let me answer the first question right off the bat and the answer is... HA! Might as well have horses pulling wagons again, because that's how old that technology is! Anti-gravity, unless its at that level or above, its a waste of time to talk about.

Bro how are u saying any of this? Lol

This guy says so much while saying almost nothing

He said we already understand everything. 😂🤣😂😂😂😂😂😂😂😂🤣🤣😂😂😂😂😂😂😂😂😂🤣😂😂😂🤣🤣😂😂😂😂

🫣 He uses fission and fusion interchangeably lol, also nothing he described involves a fusion or fission reactor, would highly recommend that no one listens to this portion of the podcast and does some actual research 👍