The final NASA budget that will emerge from Congress will likely change substantially from the request made by the Trump administration. One thing that will almost certainly not change is the cancellation of the asteroid redirect mission (ARM) that evolved out of President Barack Obama’s 2010 mandate to send astronauts to an asteroid in advance of a mission to Mars. According to "Air and Space," NASA is already planning to reuse some of the technology developed under ARM for other purposes in its plans for deep space exploration.

What was the asteroid redirect mission?

When President Obama made the decision to cancel the Constellation Program that would have landed people on the moon, the reaction from Congress and the aerospace community was far more violently opposed that he had anticipated. So, in a speech at the Kennedy Space Center, the President proposed an alternative space exploration program. The centerpiece of the program was the Journey to Mars to end in the 2030s, but in the interim Obama proposed a voyage to an Earth-approaching asteroid.

Unfortunately, NASA decided that it could not accomplish the asteroid mission for any budget that the president was proposing or Congress was approving. Thus, ARM was born.

The asteroid redirect mission envisioned sending an uncrewed vehicle to capture an asteroid and take it into orbit around the moon. Then the asteroid could be visited by a crew of astronauts in an Orion spacecraft. When that plan proved to be too challenging, it changed to snagging a boulder off of the surface of an asteroid instead of moving the entire rock.

What went wrong with the ARM?

The problem with the asteroid redirect mission was that no one outside of NASA seemed to think it was useful, including the scientific community. The purpose of the mission appears to give astronauts something to do while the hardware is developed to send them on the Journey To Mars. NASA claimed that the ARM was crucial to going to Mars because the spacecraft that would go and get the asteroid boulder would be a test of an advanced solar electric engine that could be used for interplanetary travel.

Nevertheless, Trump seems prepared to cancel the program, and Congress will likely follow suit.

What comes next?

NASA is already scrambling to repurpose the technology that was developed for the ARM for the deep space gateway it now plans to build in lunar orbit. The Solar Electric Propulsion (SEP) system could move elements of the deep space station from Earth's orbit to lunar orbit with ease. Later, a more advanced version could be used to send people and cargo to Mars. Thus, without the bother of grabbing a boulder off an asteroid, the ARM program could serve the Journey to Mars and perhaps back to the moon after all.