Podcasters: Ralph Wilkins.
Title : Awesome Astronomy: NASA’s Going Nuclear!
Organization: Awesome Astronomy
Link : www.awesomeastronomy.com; A gallery of event images can be found here: https://www.space-park.co.uk/galleries/bpsc2024/
Description: From Feb 3, 2023.
Nuclear powered rockets are about to become a reality opening up space travel for humanity. Ever since the dawn of nuclear weapons and reactors, advanced militaries and space agencies have dreamt of powering rockets with long lasting energy efficient nuclear fuel.
Damien Phillips, John Wildridge and Dustin Ruoff produce.
Bio: Awesome Astronomy explores the frontiers of science, space and our evolving understanding of the universe.
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Transcript:
It’s the 365 Days of Astronomy podcast, coming in 3, 2, 1… Intro Music This is possibly the most exciting news in space exploration right now. I am so psyched about this.
NASA and DARPA are getting the band back together to look at nuclear propulsion. Not just write a paper about it or build a grounder demonstrator, but test a nuclear engine in space to get to Mars faster. Intro Music So a trip to Mars would take 9 months to get there with conventional rockets.
You then have to stay there for 3 months to wait for a favourable planetary alignment, and then it’s another 9 months to get back. 21 months minimum, 18 of those are in travel time alone. All that time your astronauts are risking radiation exposure, mechanical failure, unanticipated medical emergencies, or any number of other catastrophic events.
But a nuclear rocket engine could significantly cut that time on paper. They should be 3 to 4 times more efficient. Now that doesn’t quite equate to being 3 or 4 times faster, but it does mean huge savings in terms of how much more equipment you can take with less fuel needed and get there much faster too.
How much faster? We’ll have to wait and find out. Isn’t this voyage of discovery fun?
Now of course, if it was as simple as all that, we’d have done this ages ago. And NASA has certainly tried. In fact, so did the Soviet Union.
They ran a nuclear rocket engine prototype program until 1986, and they have an experimental cruise missile called Burevestnik that’s nuclear powered. Over in the US, they had the conceptual Project Orion in the 1950s that took a different approach, effectively lobbing nuclear bombs out the back of a rocket and using their explosive power against the thick metal plate to propel a rocket forward. That was clearly a stupid idea, and they then turned their attentions to nuclear thermal engines under Project Rover for ballistic missiles, which then became Project Nerva, until it was mothballed in 1973, just before in-flight tests were due to be tried.
This program was quite productive, building a number of prototypes and demonstrators exceeding 300 megawatts, enough to power 70 homes for a year. A fun fact is that NASA had simmering plans to attach Nerva engines to a Saturn V moon rocket to undertake the grand journey of the solar system that the Voyager spacecraft were eventually built to undertake. Spectacularly, as it turned out.
The US Air Force and NASA then had a play around in separate programs for very different purposes in the late 80s before NASA settled on Project Prometheus to build nuclear iron engines for deep space robotic missions. Since that program was cancelled in 2005, nuclear has been out of favour until this new collaboration between NASA and DARPA to demonstrate a nuclear thermal engine in space by 2027. In this kind of engine, a nuclear fission reactor is used to generate extremely high temperatures.
The engine then transfers the heat produced by the reactor to a liquid propellant, which is expanded and released with force through a nozzle to propel the spacecraft forward. So it can reach temperatures of 4,000 degrees Fahrenheit, which would be catastrophic if the enriched uranium-fuelled reactor suffered a meltdown. But many conventional rocket engines often reach 6,000 degrees Fahrenheit without mishaps, and they’re more complex.
And of course, one of the big issues is going to be around public acceptance. People get nervous around nuclear. Even though no one has yet powered a rocket with nuclear engines, many famous satellites and rovers have been powered by radioisotope thermoelectric generators, or plutonium pigs, that act as a long-lasting nuclear battery.
There were even protests during the launch of the Cassini spacecraft in 1997 to explore Saturn, because it was powered by 33 kilos of plutonium that had to survive a rather risky launch and not explode to rain down over a wide area. Same for the Galileo spacecraft Jupiter in 1989. Surprisingly, there were no protests for the launch of the plutonium-powered Curiosity and Perseverance rovers to Mars in 2011 and 2020.
So perhaps awareness and concerns about nuclear-powered spacecraft ebbs and flows over time. And I’d be interested to know what you think about this. Is launching nuclear material on occasionally-exploding rockets reckless?
Or do you think we’ve put enough plutonium in space now to consider this safe? Because if we want to get to Mars, the NASA and DARPA test could well open up safer and cheaper deep-space missions for humans. Launching dozens or even a hundred spacecraft to provide just fuel for a single chemical rocket mission to Mars might be needed.
With nuclear propulsion, we could get that number down to just five. They also allow for more abort options as well. If you remember Apollo 13, the only real way to get back from the moon with traditional chemical rockets was to slingshot around it using the moon’s gravity to propel the damaged spacecraft back to Earth.
With the efficiency of nuclear thermal rocket engines, you have more opportunities to just turn around and begin firing in the opposite direction to get back sooner in the event of a disaster. And finally, they allow for greater reusability, something that’s been revolutionized under new commercial spaceflight companies like SpaceX and Rocket Lab. Nuclear propulsion means you need fewer refueling depots en route to Mars or other destinations in the solar system than conventional chemical rockets would need, making it an environmentally cleaner and more efficient way to refuel in space.
So once this technology has been proven out by NASA and DARPA, who knows if Musk will use nuclear engines for the upper stage of Starship or Bezos for the upper stage of New Glenn. If it increases the reusability and makes the spacecraft faster and more efficient once in space, they’d be foolish not to, wouldn’t they? NASA would need them for trips that could be reduced in time from months to weeks.
So if SpaceX want to be in with a sniff of providing the hardware to get NASA astronauts to Mars, they might have to go with this option that reduces astronauts’ travel time and brings down costs. But what do you think? Is this just like the old projects in nuclear propulsion that get shut down before they mature?
Or is it the technology needed to open up the solar system to human exploration?
365 Days of Astronomy
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