Thursday, January 26, 2012

Project High Jump Boosted Dart

How do I always miss the great projects?

Here is video footage of the attempt:

The motor failed during burn, resulting in a shred and recovery failures. This flight was one of several proposed Carmack 100kft projects. You can read more about these projects here.

The specs for Project High Jump are:

Boosted Dart configuration
4" dia 36,000ns Booster
Case bonded
Double Taper Core
Booster 7' 4" Overall length
Welded Fin Can

Dart Configuration
1.5" dia
40" Length
Fins Welded to tube

Raven Altimeters in booster and Dart
Big Red Bee 2 meter high power GPS telemetry

A boosted dart is a small, dense dart that is attached to a larger booster. On burnout the dart flies free, and is optimally designed to coast very well. Darts are dense, thin, and usually have a boat tail on the bottom. Boat tails greatly reduce base drag in the lower atmosphere, and are something like a backwards nosecone. When a rocket has a built-in motor, there is severe base drag because the bottom is typically a flat, abrupt ending to the rocket.

Boosted dart apogees can be twice as high as a regular rocket of similar impulse, perhaps higher. In one example, the Reaction Research Society (RRS) launched an R motor boosted dart that hit nearly 100 KM altitude despite burning out at about 10,000 feet. That tiny dart coasted at 4,500 fps in dense lower atmosphere, yet almost made space despite that. The dart coasted for about 50 miles! A full-sized R motor would have been lucky to get as high as 100,000 feet if it had to fly as one unit simply because drag is so serious at low altitude. By comparison, rockets typically need to hit mach 5 and 40,000 feet to get space. Darts can do it from miles lower.

It is logical to use a boosted dart for a "simple" goal like getting electronics over 100,000 feet. It is cheaper than a giant motor (the Q motor that did break 100,000 feet) and less complex than a two stage rocket. The N5800 motor is a bit slow burning for a dart, but it would certainly be enough to get a dart above 100,000 feet under the right conditions. In this case, the booster was a thin O motor that could have done a bit better than the N5800, but reliability matters also.

More images here

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