Firefly Space Systems unveils Alpha launch vehicle design with aerospike engine

By David Szondy, Gizmag



Firefly Space Systems

The signs of a healthy industry isn't just growth or innovation, but a tendency to reach out and fill niche markets. A case in point is the small satellite launch company Firefly Space Systems, which recently unveiled its planned Alpha launcher. Aimed at the small satellite launch market, it's designed to launch satellites into low-Earth orbit (LEO) at very low cost with an unconventional aerospike engine. It is also the first orbital launcher to use methane as fuel.

The launcher uses methane and liquid oxygen as propellants, which Firefly says is a first for orbital launchers, though methane has been proposed for landers. Methane was chosen because it’s cheap, plentiful, clean-burning and, unlike more conventional fuels, self-pressurizing, so it doesn't require a second pressurization system.

Alpha's aerospike engine with rocket burner cluster
However, the interesting thing is that when you look at the first stage, you see a curious bulge at the base ringed with rocket burners rather than the usual cluster of rocket engines. That’s because, while the second stage uses conventional rocket engines, the first stage uses a more exotic plug-cluster aerospike engine putting out 90,000 lb (400.3 kN) of thrust.

The plug aerospike is basically a bell-shaped rocket nozzle that’s been cut in half, then stretched to form a ring with the half-nozzle now forming the profile of a plug. The clever bit is that the open side of the rocket engine is now replaced with the air around it. As the rocket fires, the air pressure keeps the hot gases confined on that side like the wall of the bell nozzle did. As the craft rises, the change in air pressure alters the shape of the “nozzle;” keeping the engine working efficiently.

"What used to cost hundreds of millions of dollars is rapidly becoming available in the single digit millions," says Firefly CEO Thomas Markusic. "We are offering small satellite customers the launch they need for a fraction of that, around US$8 or 9 million – the lowest cost in the world. It’s far cheaper than the alternatives, without the headaches of a multi manifest launch."