Normally one of the hardest parts of making a reusable rocket is the Thermal Protection System (TPS). Because our rocket has a lower reentry temperature, we can use a simple industry standard metal alloy which lasts a long time. We don't need to go to exotic ceramic tiles that require a lot of repair every flight.
Another alloy is HASTELLOY-X which is good to 2200 Deg. F (1200 Deg. C). It seems Haynes 230 has a bit better oxidization resistance though.
But the best commercial alloy we know of is Haynes 214 which resists oxidization for long periods at 2300 F (1260 C) and short periods at 2400 F (1315 C).
Another option is to have a commercially available ceramic blanket. This could keep the heat from the main structure of the vehicle. The prices are between $1 and $10 per square foot.
For the X-33 work was done on metallic thermal-protection panels that are good to about 1,800 degrees Fahrenheit.
The ARMOR TPS is interesting. This is a metallic honeycomb sandwich panel made out of Inconel 617 which resists oxidization to about 1,800 degrees Fahrenheit (982 C). In a paper with interesting details on ARMOR they point out that the shuttle, which discards its main tank, is dense so it flies a hot reentry. A less dense reentry vehicle with lift could fly a reentry that kept below the melting temperatures of some alloys.
The following three papers are interesting;
An overview and assessment of metalic tiles.
A paper on heat shielding for orbital RLVs.
A report on metalic TPS.
A commercial coating called U2000 looks very interesting. It has been designed with reentry in mind. This coating with various ceramic matrix composites, carbon-carbon composites, and graphite substrates makes a very good TPS. It can weigh about 1.56 lbs/sq-ft.
The Space Shuttle used an aluminum frame but would have used titanium if they had a bit more money. Titanium would not have required tiles on the top of the orbiter.
Titanium was $3.44/lb in 1998, so the material cost would be under $3,000 for a 700 lb rocket. Worldwide titanium production was 240.7 million pounds in 1998. Companies like Boeing are big users. The USGS has lots of info on titanium.
An essay on the evolution of reentry technology.
The Wikipedia article on Atmospheric Reentry mentions a NACA Report 1381 about ballistic missile reentry from 1958 used to be online. When reentering the atmosphere the heat energy goes to either the air or the vehicle. In the case of a lightweight reentry vehicle the amount that goes into the vehicle is proportional to (skin-friction*surface-area) / (drag-coefficient * drag-reference-area). So the more the vehicle's drag, the less heat goes into the vehicle and the more goes into the air. A ball is actually the ideal shape.
There are Ceramic Fibers which might be interesting for making a high drag device.
Click for SpaceTethers.com
Copyright (c) 2002, 2003 by Vincent Cate. All rights reserved.