#1
|
|||
|
|||
The 100/10/1 Rule.
I've been simulating single stage to orbit (SSTO) launch to low earth
orbit (LEO) in orbiter space flight simulator for a little while now. Consider your basic space shuttle main engine (SSME) powered single stage to orbit (SSTO) rocket. Hydrogen is the most powerful chemical rocket fuel known (excluding exotics). To reach low earth orbit with a cryogenic fuel of this nature, a mass ratio of 10 to 1 is required (the 10/1 rule). That is 10 parts of fuel and oxidizer to one part rocket. After accelerating to a stable orbit roughly 1% of the fuel is remaining (more or less, depending upon the ascent trajectory profile, the launch latitude, and final orbit inclination and altitude). That's roughly 100 parts gross liftoff weight to 1 part residual fuel (the 100/1 rule) or 10 parts empty weight to 1 part residual fuel (yet another 10/1 rule). Thus the usable payload delivered to an orbital station or spaceport is roughly 1% of the gross liftoff weight, and 10% of vehicle empty weight. In this case this is fuel which can be immediately converted into energy and water (via a fuel cell), and water that can then be reconverted back (using solar energy) into propellant and oxygen. This isn't very much. However that's the reality of climbing the gravity well of Planet Earth. In order to increase this payload, the obvious solution is converting the rocket itself into payload. In this scheme the engine is removed from the vehicle (roughly 20 percent of empty weight) and returned to Earth in a cleverly designed nose cone engine carrier, and the tankage, the oxygen, hydrogen, pressurization, residual fuel tanks and the RCS - reaction control system, is then immediately pressed into service as payload for infrastructure in constructing the space station or orbital spaceport itself. Thus, the usable payload fraction is then increased by a factor of seven (7) or so, dependent upon the amount of equipment or infrastructure necessary to successfully reenter and recover a seven thousand pound space shuttle main engine (SSME) from low earth orbit. For a reasonably designed single space shuttle main engine powered single stage to orbit launch vehicle, this represents 3500 pounds of residual fuel and 25,000 pounds of infrastructure. This is not trivial. Plus, you get the engine back. Adding some GEM-60s improves the numbers. -- Get A Free Orbiter Space Flight Simulator : http://orbit.medphys.ucl.ac.uk/orbit.html |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Going Forth to Rule the World | Warhol | Misc | 0 | May 22nd 06 05:19 PM |
Is this like some kind of rule? | Rich | Amateur Astronomy | 7 | January 16th 06 12:59 PM |
Republicans Rule | Mark | Misc | 5 | May 28th 04 12:56 PM |
New newsgroup rule... | Pete Lawrence | UK Astronomy | 11 | November 11th 03 10:47 PM |
Aperture Does NOT Rule | Jon Isaacs | Amateur Astronomy | 57 | August 26th 03 01:13 AM |