Aerospike Rocket Engines- You learn something new every day.

So, yesterday I heard that a new startup in Texas was looking to build a launcher for small satellites. The company is named Firefly, and of course, a quick google search found mostly pics of Serenity and Mal Reynolds. But one thing caught my eye, was a reference to aerospike engines, which the company plans to use. That lead to the question, what the hell is an aerospike engine?

You’re familiar with a liquid fueled rocket engine, right? Let’s look  at a typical engine. The is the RS-25, a derivative of the Shuttle Main Engine intended for the future SLS platform.

Pumps mix fuel and oxidizer in a combustion chamber that then flows out the bell. Simple enough.

Aerospike engines kinda turn the bell idea upside down. The flame exhaust goes outside of a wedge, and uses ambient air pressure to shape the plume.

Confused? So was I.


In spite of extensive testing and several developmental models, the aerospike has never flown to space. Whether Firefly Systems changes that remains to be seen.

Osprey APKWS

Aviation Week & Space Technology has the story, but it’s behind the paywall.

A Marine MV-22B fires an APKWS guided rocket during trials.

The APKWS is the Advanced Precision Kill Weapon System. You have to look fairly closely to see the rocket leaving the pod mounted to the port cheek of the fuselage.

APKWS takes an unguided 70mm Hydra rocket. Hydra rockets are modular. There are various motor and warhead configurations that can be mixed and matched.  The APKWS is a guidance section. Unscrew the warhead from the motor section, screw the APKWS to the motor, and the warhead to the guidance section. Suddenly, you have a guided missile that’s very precise, and has a much longer effective range than an unguided rocket. It has a small warhead, but its quite sufficient to take out a truck, other unarmored vehicle, gun emplacement or similar target. And it is comparatively cheap, as opposed to say, a Hellfire missile.

What Might Have Been… Broncos and 106mm RCLs.

On the heels of our recent post about the M40 106mm Recoilless Rifle, a reader, Dave, sends in this little morsel about a plan to mount the 106 on the OV-10.

The primary weapon for the Bronco was usually the Zuni 5” folding fin rocket. It packed a good punch, but it wasn’t terribly accurate, and each rocket weighed a good deal.  While mounting a 106 on an airplane would have its own weight penalty, each round of ammunition would weigh less. And the recoilless rifle would be a good deal more accurate than any rocket. And there was a plan for an autoloading weapon.

Found here, which is an interesting piece all on its own.