Successful Aerospike Test

Here's a good explanation of what aerospike rocket motors are all about.

There are pictures here, and if you select the medium or large sizes, you can really study the detail of the aerospike design (if that sort of thing floats your boat).

The names and organizations involved are familiar to rocketeers, because this is the kind of cutting-edge experimentation that some of us get involved with. Here's the inside scoop from Chuck Rogers, one of the people involved, as posted on the Rec.Models.Rockets newsgroup (links added):

Cesaroni Technology Incorporated did a great job on the structural design and fabrication of the aerospike. The aerospike retrofits onto an O5100 motor in place of the conventional conical nozzle. BlackSky Research built the Optimal 168 rocket, and ran the launch operations for the flights.

I've seen the Cessaroni motors flown, and they are sweet. They're also commonly available to people like myself who fly the smaller rockets. BlackSky is another company that does everything from hobby rocketry to 'real' experimental rocketry. My launch rail was made by them.

The aerospike is a centered Prandtl-Meyer all-external expansion design. It delivered 97% of ideal efficiency in ground test (exceeding historical Rocketdyne data), and theoretically would deliver the same high efficiency from sea level to vacuum flight conditions.

Even the most optimized conventional nozzles are compromises for the expected range of altitudes and pressures expected. The efficiency of the aerospike means that bigger payloads can be lifted on a given thrust.

The rocket flights were to demonstrate operation of the aerospike in flight, and to measure installation effects compared to the uninstalled ground static firings. CFD was run not only for the aerospike hot gas flowfield, but for the combined rocket and aerospike plume flowfield.

This is the most highly instrumented high power/experimental rocket ever flown. In addition to highly accurate accelerometers and pitch, yaw, and roll rate sensors, the rocket used a conic nosecone with a built-in Flush Air Data System (FADS) (like a pitot tube), calibrated with CFD and cone pressure tables. This was the first inflight direct aerodynamic measurement of angle of attack on a model, high power, or experimental/amateur rocket.

Blacksky Research coordinated the development of the aerospike nozzles and solid rocket motors, provided overall project management on the contractor side, and really helped refine the whole concept of using large high power rockets for advanced flight test research. All at a low cost relative to normal government aerospace projects.

All that fun and saves Uncle Sam money too. Later on in the exchange, questions about the materials used to construct the aerospike were asked. This is why I love rocketeers, because Anthony Cessaroni himself jumped into the conversation:

Composites, ferrous and non-ferrous alloys, a little bit of graphite and a pinch of tungsten.

We also got to hear about one of the hazards of aerospikes (Chuck Rogers again):

Well, it turns out that the tungsten tip on the aerospike is REALLY SHARP. While walking around the rocket as it was mounted on the transfer cart I got "speared" by it. It put a tear in my shirt, but it didn't break the skin. It did not draw blood!

For this experiment we wanted a "pure" spike that went all the way to a sharp tip. For an "operational" aerospike there is predicted to be very little performance loss for up to a 25% reduction in the spike length.

You'd want at least some minimal truncation to avoid that VERY sharp tip.

Which was suggested by CTI, but again, for the "purity" of the experiment we wanted a sharp tip.

These are the kind of details that bring history to life. And to add a data point to our assertion that hobby rocketry leads to technology-related careers, here are two pages from a 1982 rocketry magazine written by "Crazy-Chuck" Rogers.

Posted by Ted at May 10, 2004 05:22 AM
Category: SciTech