Conference 7.286::space

915.0. "Two Stages To Orbit - TSTO" by MAYDAY::ANDRADE (The sentinel (.)(.)) Fri Jul 08 1994 15:37

    
    	Note 913 reminded me, that first stages don't have to impart
    	lots of velocity to the second stages in order to help out.
    	It is enough that they bring it out of most of the atmosphere.
    
    	I know that SSTO's are the rage these days, but the truth is
    	that two stages still are a lot easier, safer, and less costly
    	do deliver with the current state of the art.
    
    	So can anyone tell me what is wrong with the following ?
    	Not only would you get a nice cheap orbiter, but also a big
    	hunk of a Jet transport trown in for free.
    
    	Gil
    
    
    
    
		Two Stage To Orbit - Using air breathing first Stage
		====================================================


	First Stage Horizontal Take-off and landings can simplify things.
	(As there is no requirement for the 1.3 Vertical-Take-Off-Thrust
	factor. The First Stage can then just be a regular Jet Plane.)

	Example: Of a two stage fully re-usable design

	Stage 1: 	(Jet) - Horizontal take-offs and landings
        :
	:		240 [stage 2]  + 80 [Ship] + 45 [Kerosene]
	: 		Horizontal Take-Off mass  = 365 Metric Tons
	: 		Ship/Propelant mass ratio = 177.8%
	: 		Delta Velocity delivered  = 2.5 Km/s
        : 	
	..............  Delivers "Stage 2" to 15 Km Altitude and 0.5 Km/s

	Stage 2:	(Rocket) - Vertical Landings
	:	
	:		10 [cargo] + 30 [Ship] + 200 [LH2+LOX] = 240 Tons
	: 		Ship/Propelant mass ratio = 15.0%
	: 		Delta Velocity delivered  = 8.0 Km/s
	: 
	:.............	Delivers "10 Cargo Tons and 2 Astronauts" to LEO


	*    A SSTO [LH2+LOX] requires a Ship/Propelant ratio = 9.0% 

	***  Drawback:  Have to Develop and Operate 2 stages/vehicles.

	***  Advantages:  

	No need tp push the state of the art in structural material's
	technology to reduce the Ship/propelant mass ratios. Design
	could be build using current materials and big safety margins.

	The "Stage 1 - Jet Plane" can be used to ferry the 
	"Stage 2 - Rocket Orbiter" between Earth locations. Thus, no 
	need for a separate transport plane.

	The Stage 1, can also be used as a heavy duty transport plane, by 
	the military or comertial sectors. Using container boxes, that 
	could be quickly  attached or detached. (Under its carriage, with 
	the same attachements as the "Stage 2 - Rocket Orbiter").

	The Stage 2 Boost Engines Could be "2 Space Shuttle Main Engines".
	Massing just  3.18 tons each they deliver 1.667 MN Sea Level and 
	2.093 MN Vacum thrust. Enough that they only need be used in low 
	throttle modes to increase their reliability and life times.

        ..................................................................

	 "Stage 1 - Jet  Transport"		        X : Boost Engines
         "Stage 2 - Rocket Orbiter"     |	        x : Orbit & Land   
	                 	        |                   Engines (.4 MN)
                       =======@=@=@===========@=@=@=======         
                                   | /~~x~~\ | 
	 With landing gears        |( X x X )|          = : Body/Wing  
         down.  Back View.         | \__x__/ |          @ : Jet Engines
                                   W         W          W : Wheels
        ..................................................................
	                                 
	Gil Andrade
	08-Jul-1994

I think Boeing is working on something very similar right now.  Perhaps stage 1
is a sst in the Boeing design tho.

Tony