A radiator as long as a football field, to be built directly in space. That is the idea NASA is exploring to speed up a trip to Mars using nuclear electric propulsion, which today would require years spent in the hostile environment of deep space.
The project is called MARVL, short for Modular Assembled Radiators for Nuclear Electric Propulsion Vehicles. It is being developed by NASA centers together with external partner Boyd Lancaster and aims to break a key component of nuclear propulsion into more manageable modules. NASA has already approved funding for two years of early-stage research.
Nasa Rocket Test
The heat problem
A nuclear electric propulsion system must get rid of the heat produced by the reactor that powers it. The leading design calls for a huge array of radiators, roughly the length of a football field once deployed, to release that heat into space. The problem is that a structure this size, even fully compacted, is still too big and unwieldy to fit inside a rocket.
Pieces launched separately, assembled in orbit
MARVL's solution is simple in theory: if the radiator cannot launch as a single block, send it up in parts and have robots assemble it once in orbit. The method requires several launches, but it frees the parts from the size limits of the launch vehicle. Once the panels are connected, a liquid metal coolant, such as a sodium-potassium alloy, flows through them and dissipates the heat generated by the propulsion system.
The challenge remains enormous, but it plays to the robotics expertise NASA has built up over the years.
The spacecraft itself changes shape
The approach could also influence the design of the spacecraft itself. Julia Cline, a mentor on the project in NASA Langley's Research Directorate, notes that existing vehicles never considered in-space assembly during design. "We have the opportunity to say: we're going to build this vehicle in space. How do we do it, and what does the vehicle look like if we do that? I think it's going to expand what we think of when it comes to nuclear propulsion."
A full-scale nuclear spacecraft is still far off. Prototypes like MARVL, however, are bringing the missing pieces of the puzzle into reality.
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