America’s F-15 is an unparalleled success as an air superiority fighter. Since its introduction in the 70s, not one has been lost to an enemy aircraft in combat. Now, without real foes to speak of, it makes sense that DARPA, the Pentagon’s future-looking research wing, would want to find a new use for F-15s.
The scheme: launching small satellites from the belly of fighter jets already high in the atmosphere. And after a second explosion, that plan is no more. The holy grail of small satellite launch is a cost of $1 million or less per launch, and DARPA’s been chasing it for years.
The F-15 offered the potential to launch small satellites from anywhere the powerful fighter could reach, which was most places. But before the testing of fighter-borne launches could proceed, a specific rocket fuel had to work. And at two tests this year, that fuel failed.
Space News reports:
“The magic” in Boeing’s design, as DARPA officials described it, was the powerful nitrous oxide-acetylene propellant, also known as NA-7. The propellant would be “pre-mixed” to reduce the plumbing needed on the rocket, enabling it to carry more payload.
Boeing led two subsystem tests in Promontory, Utah, one in August and one in April, aimed at learning how the pre-mixed propellant reacted to different temperatures, pressures and atmospheric conditions. In both tests, the propellant exploded.
Without a stable propellant, DARPA has abandoned plans to use the F-15 as a satellite mothership. Instead, they will pursue small satellite launch through other means, such as an experimental spaceplane.