Why Nuclear Rockets Are Going To Change Spaceflight

Lol. "Engine-rich exhaust."

"Machined down uranium rods..." sounds like a great career path

14:57 When you are talking about Xenon poisoning of a nuclear core, I have actually seen that first hand. I saw in onboard the USS Salt Lake City while we were at power and sailing down the coast of California. We had been up north engaging in training exercises tracking ships transiting to and from Seattle. After we completed our training, we turned south to return to our homeport in San Diego. We had been traveling for an extended period of time at all ahead full. Reactor power was pretty much at 100% during this time. I was standing watch at the time as the Throttleman in Maneuvering, the room from which the reactor was overseen and controlled from. We got the order to come off the bell down to ahead 1/3. The captain wanted to tow the radio line so he could download the ships mail. While we were at this low power, because our reactor core was so old, the Xenon quickly began to build up from all the fission products we had been producing at high power. So long as we stayed at high power, the neutron flux was sufficient to burn it off as fast as it was made. But, now that wasn't the case. The neutron flux was too low. So the result was that the temperature in the reactor began to drop. As this continued, the Reactor Operator had to gradually pull the control rods out of the core to keep the temperature stable. Eventually he had pulled all the controls completely out and still the Xenon transient was continuing, dropping core temperature. At that point the Reactor Operator informed the Engineering Officer of the Watch, "Sir, unable to keep reactor temperature in the green band due to Xenon transient. Reactor rods fully withdrawn from the core. Recommend to Con to pull in the com wire and come up on the bell or else the reactor is going to shut itself off." Was both cool and funny to see such a large scale direct example of nuclear physics in action. The EOOW, the officer in charge, relayed the Reactor Operators recommendation to the Con. The Captain, then quickly ordered the line brought back in and decided he could finish reading and responding to the mail once we were back in port. About 5 minutes later I got the order to come back up to all ahead 2/3 then back to full shortly later. Temperature continued to drop for a short bit, but once back at power, quickly stabilized and returned to normal as the remaining excess Xenon was burned off. Eventually we arrived back in port, and aside from getting to watch physics in action, none the worse for the experience.

Scott, I saw this last night and wanted to personally THANK YOU. My uncle (deceased) was the chief on-site safety engineer for the NERVA/KIWI program, testing the KIWI's in Area 21, Nevada Test Site, Jackass Flats. My uncle took me out there after the program had shut down, and I saw the hot cells where they did disassembly of the reactor core, post test. I got to try out the remote manipulator arms-my uncle is at least partially responsible for my becoming an engineer, with physics deeply ingrained (Electrical Engineer). I was probably about 12 or 13. I had NEVER seen the films you show in this video, particularly with such clarity. THANK YOU. Uncle Jim was very proud of the NERVA program it was very successful, and not a waste of taxpayers money. I think the longest consecutive burn was 15 minutes continuous - the engine was still in fine shape, that was the length of the test. Later, I went to work as a young engineer, right out of college (graduated in 1974) at the site (NTS), working timing and firing for sub-surface and tunnel shots. I'm glad that the hard work of the NERVA team will finally come to fruition. Thanks again, this would have pleased my uncle. 💗

I originally wanted to be an aerospace engineer. But when the space program was cut back in the 1970s and the “energy crisis” was upon us, I switched to nuclear engineering hoping that nuclear rockets would come back. It never happened and I worked for 35 years in commercial nuclear power doing physics and safety analysis as well as writing software for real-time simulators. I guess I was born 30 years too early or 30 years too late. I remember one of our homework problems involved determining the startup rate for a nuclear rocket considering the reactor kinetics (just a simple point kinetics model). That was the closest I came to my childhood dream.

"Engine rich exhaust" is probably the funniest thing I'll hear today.

'As the delta V requirements get bigger, eventually the tyranny of the rocket equation will win' - what an incredibly eloquent statement. I love watching your videos Scott

22:00 ROFL “…you get a very spectacular type of engine rich exhaust” thank you for that phrase.

"Uranium plasma"? Fly safe indeed.

Only someone from Scotland would explain a nuclear reactor using golf analogies

I've seen engine rich exhaust. A lovely green from the copper...

I remember reading a book about nuclear rocket engines back in the 80's. It had photos of the engines on test stands at Marshall Space Flight Center, and talked about how good they were proving to be. The librarians pulled it from the shelves, and out of the card catalog. They "filtered" a lot of books like that.

Hello Scott, I have been watching your videos for years, all the way back since the Interstellar Quest series on KSP! In that time, I have received a BSc in astronautical engineering and am now currently halfway though a MSc in nuclear engineering all because of you, KSP, and the goal to work in NTP. During my undergrad I was fortunate enough to work with professors on research in both solid core and liquid core NTP designs but the craziest part is that tomorrow at 9am I start a fellowship with the Center for Space Nuclear Research where I will be working on developing a gas core NTP engine design for the next 10 weeks. Your videos are always phenomenal and this video is no different. I can't thank you enough for all the years of youtube videos and the motivation to pursue NTP.

The thing I love most about NERVA is how confidently it tries to lead up to a MINERVA engine.

"The tyranny of the rocket equation" is one of my favorite phrases.

I appreciate that Scott's personality and engineering mindset give him the confidence to publically state "at some point, if we want to go further, nuclear thermal propulsion will be the only viable option". It doesn't even matter if the statement turns out to be true or false. We are absolutely going to need the kind of people who think "right, current options can't get us to where we need to be, what do we have lying around here that can?", and this is a great example of that.

And we get all the way back to Clark's suggestion that Discovery and other ships like it would use ammonia rather than hydrogen as fuel. The man really was brilliant.

no joke last night i was looking into nuclear thermal engines and i was quite disappointed to see scott didn't have a video on them, glad to see my prayers have been answered

I once read about Project Pluto, a test program for a nuclear ramjet-propelled cruise missile that could fly at Mach 3 for days on end. Downside is the highly radioactive exhaust. I for one am glad to live on a planet with no flying Chernobyl disasters.

This was great to watch, very informative as well. While I have spent many hours studying chemical propulsion systems this has peaked my interest. I really hope you will do a deeper dive in regards to nuclear propulsion. A huge thanks to you Scott for making this for us to watch. You’re the man !!!