DARPA has released a shiny new video of the ALASA (Airborne Launch Assist Space Access) concept. The video seems to show a different design than that described HERE, which describes the vehicle as using the same engines for both the first and second stages (thus why there are four “tractor” rockets). The vehicle would ditch the first stage propellant tanks and use the same engines for stage 2. But the video shows the first stage dropping off and takign the engines with it. This would seem to negate the value of using tractor rockets. Also, the propellant is said to be a mix of nitrous oxide and acetylene, mixed together and chilled, in a single tank. This would make the design simple. But it seems a little spooky to me; acetylene has the unfortunate habit of detonating on its own unless stabilized; perhaps nitrous oxide does that. Propellants made from mixes of liquid oxidizers and liquid fuels have been made to work before, but there are definite safety concerns.
Feb 062015