SLS could launch a sample return mission to Phobos and Deimos

Universe Today

NASA’s next colossal rocket, the Space Launch System (SLS), recently had its first successful flight in November after years of development. Much of that development was done by aerospace contractors like Northrop Grumman and Boeing, so it’s a good bet that the engineers at those companies want the SLS to be seen as a success. One measure of his success will be the number of missions he can help launch successfully – the more missions, the better. To help plan some of these missions, a pair of Boeing engineers wrote a paper describing an outline of a sample return mission to Phobos and Deimos. And, of course, it was going to be launched by the SLS.

Phobos and Deimos, the two moons of Mars, are unique in a number of ways. Phobos itself is estimated to be ? empty; it has a huge crater on one side that takes up nearly half the surface, which was named Stickney after the maiden name of the wife of the astronomer who discovered it. Even better: it’s the closest moon to its host planet. Deimos is slightly less interesting but could still serve as a functional forward base for future exploration of the Red Planet.

Getting there requires some energy, though. Launching any craft, let alone one with enough fuel to return to Earth after landing on a body, would be difficult. However, as Benjamin Donahue and Matt Duggan, two of Boeing’s SLS engineers, explain in a paper, the SLS could not only bring such a mission into the Martian system, but also simultaneously launch an Orion crew module.

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There is already a mission in the works from JAXA to bring back a piece of Phobos, as explained by this UT video.

The SLS has another payload system called (with a bit of irony) the Universal Spacecraft Adapter (USA). Allows other spacecraft to co-manifest with an Orion capsule on an SLS mission. In the case of the Phobos/Deimos sample return mission, the vehicle would have four different parts.

The first would be the Mars Airbrake Module, which allows the vehicle to slow down to a highly elliptical parking orbit in the Martian system. It makes that orbital transition after using Earth’s Moon and Earth itself for gravity assist on the way to Mars. Once he arrives and completes his aerobraking duties, he is discarded.

Which leaves the descent form open. He is responsible for landing the craft on the surface of Phobos and Deimos. It carries the other two vehicle components and the science packages, which may include small rovers. It has engines powerful enough to keep the vehicle from slamming into the side of the Martian moons, but it eventually runs out of fuel after descent to Deimos (the second moon to visit).

After the samples have been collected on both Phobos and Deimos (and their science payloads left behind), the ascent module takes over by launching from Deimos and bearing toward Earth. It then separates from the last of the four modules, the Earth Return Capsule (ERC).

Depictions of the Phobos/Deimos sample return mission launch and cruise configurations.
Credit: Donahue and Duggan

The ERC is responsible for the journey back to Earth and their reentry. It consists mostly of a heat shield and some maneuvering thrusters and takes up only a small percentage of the total package weight. However, it is probably the most critical phase of the mission as, without it, the samples never successfully return to where they can be analysed.

So far, engineers have mapped out reasonable paths and trajectories, including delta v calculations for the mission, as well as the expected weight of each of the listed components. However, there weren’t many details about which samples would be the mission’s goal to find, nor any indication that a major space agency would back the mission.

But with the advent of the SLS and other superheavy launchers like Starship, these types of missions will no longer be prohibitively expensive in some cases. It’s only a matter of time before we visit the surface of these two extraordinarily unique moons.

Learn more:
Donahue & Duggan – A Phobos and Deimos sample return mission launched as a co-manifested payload on NASA’s SLS launcher
UT – What could we learn from a mission to Phobos?
UT – JAXA’s ambitious mission for Phobos will even have a Rover built in Europe
UT – Do you want to explore Mars? Send humans to the moons of Mars first: Phobos and Deimos

Main picture:
The Mars Reconaissance Orbiter (MRO) captured this image of Phobos and Stickney Crater in 2008.
Credit: NASA/JPL-Caltech/University of Arizona

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