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DARPA XS-1 space plane could allow rapid deployment of satellites, fuel depots

According to a Monday story on DARPA, the Defense Advanced Research Projects Agency, is having another go at developing a space plane that can deliver a payload to low Earth orbit, land, and then be rapidly turned around to do it again. The dream is as old as the original space shuttle program, but has thus far eluded researchers. Three teams have been selected to pursue initial study contracts.

Space fuel depot concept
Space fuel depot conceptNASA (public domain)

The teams are Northrup Grumman and Virgin Galactic, Masten Space Systems and XCOR Aerospace, and Boeing and Blue Origin. The goal is to develop a reusable, two stage space plane that can deliver a payload of 3,000 to 5,000 pounds to low Earth orbit that can be launched 10 times in 10 days at a cost of $5 million per launch. The technical challenges to build such a vehicle, which would operate like an airplane, are mildly speaking challenging.

Both the government and the private sector have been pursuing the goal of developing a spacecraft that can be launched cheaply and frequently for decades. The space shuttle was, at one point, touted as a vehicle that could fly 50 times a year, a goal it never achieved. More recently, SpaceX is attempting to make its Falcon 9 a reusable vehicle, allowing the various stages to fly back and land rather than be ditched in the ocean.

The development of a space plane would be a game changer insofar as the ability to deploy payloads in space. The Defense Department would be able to rapidly replace satellites that were destroyed either by misadventure or by enemy action during wartime. This is a consideration with China testing an anti-satellite weapon.

The space plane might also have an effect on space exploration. One approach touted by many for sending spacecraft into deep space has been to eschew a heavy lift rocket in favor of orbiting fuel depots. The idea is that fuel being the bulk of a spacecraft’s mass, one could send it to an orbiting depot where it could be stored. Then a spacecraft could be launched on an existing commercial rocket, fuel up at the depot, and then proceed on to the moon or an Earth approaching asteroid.

The scheme has fallen short due to the flight rates of existing vehicles. A study often touted by proponents of fuel depots notes that because of relative low flight rates of existing launch vehicles, only three expeditions to the moon and/or an asteroid could be completed per decade using the scheme. This would severely limit the amount of space exploration that could be done.

But a space plane based on the XS-1, which could fly once a day, would change that formula. A fleet of such vehicles could keep an orbiting fuel depot constantly topped off, allowing deep space expeditions using smaller, commercial rockets to be launched practically at will. The architecture could even extend the reach of a heavy lift rocket, such as the Space Launch System. Allowing for larger, heavier spacecraft to be deployed,