The growing list of potential smallsat launchers thinned out a bit last week with the news that DARPA, the Defense Advanced Research Projects Agency, has cancelled ALASA, the Airborne Launch Assist Space Access program which was awarded to Boeing in 2014. The story, reported in Space News, cites difficulties in maintaining safe control over the high performance, but even higher risk NA-7 propellant intended to power the 45 kg payload capacity booster as the reason.
According to the report, two ground tests of the nitrous oxide /acetylene propellant combination, which would have been pre-mixed before launch in a bid to simplify the vehicle’s plumbing, resulted in explosions.
Had the program, the overall goals of which were to achieve 24 hour launch capacity for under $1 million per flight proceeded as planned, it would have seen as many as 12 test flights beginning in early 2016. Given that the operational plan called for a piloted F-15E to carry the rocket to a launch altitude of 12,000 meters, the propellant instability proved problematical.
ALASA follows two previous small launcher projects by DARPA into the history column without producing flight hardware, but comes at a time when the broader commercial market is offering solutions similar to those contained in the objectives, albeit at a higher price point. Atlanta based Generation Orbit is developing GOLauncher 2, a small, two stage, air launched rocket which will be carried aloft by a Learjet 35. In 2013 NASA’s Launch Services Program awarded to Generation Orbit and GOLauncher 2 a contract for the launch of three 3U cubesats to take place in August 2016 from Cecil Field Spaceport in Jacksonville, Fla. At 100 lbs to LEO and launch to any inclination, its capacity is nearly identical to that of ALASA, suggesting that if DARPA wants to take a more conventional route they know who to call.
One issue with the sort of high risk/high reward programs of the type that DARPA is commissioned to undertake, is that they often incorporate multiple advancements at the same time, and if a given program is cancelled over difficulties with one element, it may prevent other elements from being tested as well. In this case, ALASA’s rocket featured an unusual configuration in which the same set of rocket engines powered both the first and second stages by virtue of being mounted to the second, with the first stage essentially being a propellant drop tank. As a somewhat unique solution to reducing the vehicle’s mass, it would be interesting to see developed.