RGClark
Mathematician
- Joined
- Jan 27, 2010
- Messages
- 1,635
- Reaction score
- 1
- Points
- 36
- Location
- Philadelphia
- Website
- exoscientist.blogspot.com
Hello. I found this forum after a web search on the space shuttle orbiters capabilities. I copied below something I've been discussing on other space oriented forums. Any feedback positive and negative is appreciated.
Here's an article that describes the plan to sell the orbiters minus engines for $42 million:
For sale: Used space shuttles. Asking price: $42 million apiece.
By John Matson
Dec 18, 2008 04:00 PM in Space
http://www.scientificamerican.com/blog/post.cfm?id=for-sale-used-space-shuttles-asking-2008-12-18
It is currently intended only to be sold to educational institutions, or governmental agencies.
The Air Force is looking for designs for reusable first stage boosters for two-stage-to-orbit (TSTO) systems. Then it might be able to be used for this purpose. Most likely you would use kerosene fuel for this since dense fuels are more suitable for first stages.
The payload bay would be converted to a fuel tank, and the second stage of the TSTO would be carried on top or below the orbiter. High performance kerosene engines such as the Russian NK-33, with a near legendary thrust/weight ratio of 136.66 to 1 at a weight of 1,222 kg, could be used for propulsion:
NK-33.
http://www.astronautix.com/engines/nk33.htm
The orbiter without the SSME engines masses around 68,600 kg:
Atlantis.
http://www.astronautix.com/craft/atlantis.htm
Its payload bay is around 300 cubic meters that could be used for propellant. Using the densities of kerosene and lox given here:
Lox/Kerosene.
http://www.astronautix.com/props/loxosene.htm
and the oxidizer to fuel ratio of the NK-33 of 2.8 to 1 we can calculate the propellant load that can be carried as about 300,000 kg. You would need at least 3 of the NK-33's to lift this fuel load, orbiter and second stage.
The tank weight of kerosene/lox is typically around 1/100th of the propellant weight so around, 3,000 kg. Then the empty weight of the reconfigured orbiter would be 68,600kg + 3*1,222kg + 3,000kg = 75,266kg. And the fully fueled weight of this stage would be 375,266kg.
For this first stage alone without a second stage, this would be a mass ratio of about 5. Using an average Isp of the NK-33 of 315 you could get a delta-V of 315*9.8*ln(5) = 4,970 m/s, about Mach 15.
A total delta-V this high raises the possibility it could be used for suborbital tourism or point-to-point hypersonic transport, if sale to commercial organizations were to be allowed.
In regards to its feasibility, keep in mind that the orbiter is a rocket after all. And it does have it's own engines. After ET separation it is essentially operating in the fashion I'm suggesting with it's own on board fuel supply, albeit with much weaker OMS engines.
Remember with the current shuttle with the ET still attached after the SRB's jettison, that 1,000,000 lbs thrust from the SSME engines is being transmitted up through the airframe, so the orbiter has to be built already quite rugged to withstand these loads. Then it is already operating as a rocket with much higher thrust than what I'm suggesting and the aerodynamic stresses and structural loads are even worse than in my scenario since the ET would carry even more fuel and it is in a non-axial position. What I'm suggesting is actually *easier* than the current propulsion method of the shuttle system after SRB separation.
Bob Clark
Here's an article that describes the plan to sell the orbiters minus engines for $42 million:
For sale: Used space shuttles. Asking price: $42 million apiece.
By John Matson
Dec 18, 2008 04:00 PM in Space
http://www.scientificamerican.com/blog/post.cfm?id=for-sale-used-space-shuttles-asking-2008-12-18
It is currently intended only to be sold to educational institutions, or governmental agencies.
The Air Force is looking for designs for reusable first stage boosters for two-stage-to-orbit (TSTO) systems. Then it might be able to be used for this purpose. Most likely you would use kerosene fuel for this since dense fuels are more suitable for first stages.
The payload bay would be converted to a fuel tank, and the second stage of the TSTO would be carried on top or below the orbiter. High performance kerosene engines such as the Russian NK-33, with a near legendary thrust/weight ratio of 136.66 to 1 at a weight of 1,222 kg, could be used for propulsion:
NK-33.
http://www.astronautix.com/engines/nk33.htm
The orbiter without the SSME engines masses around 68,600 kg:
Atlantis.
http://www.astronautix.com/craft/atlantis.htm
Its payload bay is around 300 cubic meters that could be used for propellant. Using the densities of kerosene and lox given here:
Lox/Kerosene.
http://www.astronautix.com/props/loxosene.htm
and the oxidizer to fuel ratio of the NK-33 of 2.8 to 1 we can calculate the propellant load that can be carried as about 300,000 kg. You would need at least 3 of the NK-33's to lift this fuel load, orbiter and second stage.
The tank weight of kerosene/lox is typically around 1/100th of the propellant weight so around, 3,000 kg. Then the empty weight of the reconfigured orbiter would be 68,600kg + 3*1,222kg + 3,000kg = 75,266kg. And the fully fueled weight of this stage would be 375,266kg.
For this first stage alone without a second stage, this would be a mass ratio of about 5. Using an average Isp of the NK-33 of 315 you could get a delta-V of 315*9.8*ln(5) = 4,970 m/s, about Mach 15.
A total delta-V this high raises the possibility it could be used for suborbital tourism or point-to-point hypersonic transport, if sale to commercial organizations were to be allowed.
In regards to its feasibility, keep in mind that the orbiter is a rocket after all. And it does have it's own engines. After ET separation it is essentially operating in the fashion I'm suggesting with it's own on board fuel supply, albeit with much weaker OMS engines.
Remember with the current shuttle with the ET still attached after the SRB's jettison, that 1,000,000 lbs thrust from the SSME engines is being transmitted up through the airframe, so the orbiter has to be built already quite rugged to withstand these loads. Then it is already operating as a rocket with much higher thrust than what I'm suggesting and the aerodynamic stresses and structural loads are even worse than in my scenario since the ET would carry even more fuel and it is in a non-axial position. What I'm suggesting is actually *easier* than the current propulsion method of the shuttle system after SRB separation.
Bob Clark
