SpaceX Gets a Contract for Something They've Never Done

Something SpaceX has never done?  That can't be a very long list. It's got to be easier to list the things they haven't done than what they have.

That's the opening to an article on Ars Technica by Stephen Clark that "NASA awards SpaceX a contract for one of the few things it hasn’t done yet." So what is it?  Launch a nuclear powered payload to the outer planets; in particular the Dragonfly rotorcraft mission to the alien environment of Saturn's largest moon, Titan. We had a fairly deep introductory post about Dragonfly just over a year ago and as the mission is getting closer, it became time to choose the launch vehicle and how it would all be done.  At the end of that post, I pulled a SWAG that the mission wouldn't be until the 2030s. It's looking more like 2028.  NASA awarded the $256.6 million contract Monday, Nov. 25.  

The nuclear power source is a Radioisotope Thermal Generator, RTG, powered by the decay of Plutonium-238, and most folks will know these are nothing new.  RTGs have flown on many previous space missions, including NASA's Perseverance and Curiosity rovers on Mars, the New Horizons spacecraft that beamed back the first up-close views of Pluto, and the long-lived Voyager probes exploring interstellar space.  All of these were launched on vehicles that are either retired, like the Titans or Space Shuttles, or on the verge of retirement like the Atlas V.

That means it's getting to be time to certify some new vehicles. The process has started on ULA's Vulcan and the next vehicle will be the Falcon Heavy.  The Heavy has been completely successful; it has flown a relatively small number of flights, only 11, but they have all been successful.  An important consideration is that the FH is based on the Falcon 9, which is rated to ferry people into orbit - a very high level of confidence - and the most launched vehicle in the world.  NASA already certified Falcon Heavy to launch its most expensive robotic missions, such as the Europa Clipper mission, which launched last month.

That said, there's another level of certification that needs to be done for the RTGs.  This includes a review of the rocket's explosive Flight Termination System (the FTS mentioned during every launch) to ensure it won't damage the payload and cause a release of radioactive plutonium.  

Personally, I wasn't aware that RTGs were still an option. I thought the anti-nuclear power people had somehow gotten NASA to forbid their usage, but it's more the case that missions have gotten away with not using them. Consider Europa Clipper, mentioned just above.  That mission is going to Jupiter, where the solar power is a small fraction of the 1200 Watts/square meter near Earth. Europa Clipper just designed and implemented enormous solar panels (picture of one side at the bottom here).  Dragonfly introduces complications that rule the bigger panels out.  First off, it's going to Saturn where there's less power per square meter than Jupiter and Europa. Saturn and Titan are 10 times farther from the Sun than the Earth is.  More importantly, though, is that Dragonfly is going into the atmosphere of Titan and that will reduce the available power even more.

Dragonfly artist's concept on the surface of Titan. Credit: NASA/JHUAPL/Steve Gribben 

For a bit more background on the Dragonfly mission itself, I'll hand it over to Stephen Clark.

The Dragonfly rotorcraft will launch cocooned inside a transit module and entry capsule, then descend under parachute through Titan's atmosphere, which is four times denser than Earth's. Finally, Dragonfly will detach from its descent module and activate its eight rotors to reach a safe landing.

Once on Titan, Dragonfly is designed to hop from place to place on numerous flights, exploring environments rich in organic molecules, the building blocks of life. This is one of NASA's most exciting, and daring, robotic missions of all time.

After launching from NASA's Kennedy Space Center in Florida in July 2028, it will take Dragonfly about six years to reach Titan.