Author Topic: How advantageous is density in propellant for Earth to orbit?  (Read 6226 times)

Offline mlorrey

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Back to the original thread, density of propellant is very important in reducing vehicle size, dry mass, and cost. As important is to preserve as high an Isp as possible while densifying the fuel. For instance, Shuttle SRB propellant is very dense compared to kerosene, but its Isp is significantly less, thus reducing the payload capacity, and why Ares I requires an upper stage of significant size.
A launcher using the hybrid fuels of SS1 would never be able to make orbit, no matter how many stages such a vehicle had using the same fuel. It's Isp is just too low.

So you want to preserve a similar Isp as, say, Kerosene, or better, while having a more dense propellant, or a higher Isp that allows for slightly less density. Methylacetylene (the primary component of welders MAPP gas) is one such option. UDMH is another which is commonly used in launchers.

http://www.dunnspace.com/alternate_ssto_propellants.htm

Here's some good data on high performance high density fuels.

Then you can densify these fuels further with additives. You can gell them with boron or aluminum powders if you are using a pressure fed or a piston pump fuel feed system. Turbopumps tend to dislike additives and experience coking problems, which is bad if you intend to reuse them.

The smaller your vehicle, the less expensive it will be to develop and maintain. It will also take less time to develop, which is important when it comes to national politics, as new presidents have a tendency of wanting to reinvent the wheel every 4-8 years, one reason why it's taken 25 years to build a space station and we've been trying to build a replacement for the space shuttle for 20 years.

Limiting your development time to less than 8 years on 80% of the funding you really want is essential to political success in the launch business.
« Last Edit: 11/02/2009 05:34 pm by mlorrey »
VP of International Spaceflight Museum - http://ismuseum.org
Founder, Lorrey Aerospace, B&T Holdings, ACE Exchange, and Hypersonic Systems. Currently I am a venture recruiter for Family Office Venture Capital.

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