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Single Stages That Could Go All The Way



 
 
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  #1  
Old February 27th 06, 04:45 AM posted to sci.space.tech
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Default Single Stages That Could Go All The Way

I've read that there are stages of rockets that have actually flown
that had a high enough ISP and mass ratio they could have gone to
orbit if they did not need to carry a payload. In other words, if
someone had fired off the first stage of the Saturn 5, it could have
made orbit all by itself except it was carrying the rest of the rocket.

Is this true? Can someone offer some examples? And what practical
problems (like bringing along an aerodynamic shield for the nose) might
one encounter in real life.

Note, I'm not asking about hypothetical SSTO rockets, but real flown
stages.

-Charles Talleyrand

  #2  
Old March 15th 06, 08:41 PM posted to sci.space.tech
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Default Single Stages That Could Go All The Way

Probably the closest actual case was the original Atlas, which reached
orbital velocity with the entire fuel tank but without its booster
engines.

For true SSTO with nothing dropping off, the best bet would be the
Delta IV core stage, because of its long burn time and extremely high
ISP. It is the only rocket that can take off with hydrogen fuel alone
(no strap-on boosters).

Without the second stge, the core stage could probably get into orbit
assuming it didn't exceed aerodynamic pressure limits on the way up:
Gross Mass: 226,400 kg. Empty Mass: 26,760 kg. Thrust (vac): 337,807
kgf. Isp: 420 sec. Burn time: 249 sec. Isp(sl): 365 sec. .

  #3  
Old March 15th 06, 08:42 PM posted to sci.space.tech
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Default Single Stages That Could Go All The Way


I don't know of a true SSTO; Atlas approached this by dropping the
mass of its booster engines and could put 3000 lbs into low orbit, a la
Mercury. Saturn V could put a much larger mass into orbit doing the
same thing. I've heard the claim that Titan II could do SSTO, thanks
to high density propellant. Possibly either EELV could, but the payload
would be relatively small for the expense and circularization of the
orbit would be tricky, unless the payload could do the last 1% of the
burn.

Bottom line: true SSTO via existing launchers is possible, but not very
practical. We're fighting the limits of chemical propulsion all the
way.

--Damon

  #4  
Old March 15th 06, 08:43 PM posted to sci.space.tech
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Default Single Stages That Could Go All The Way

Remember, they flew an entire Atlas missile into orbit in 1958.
(Whether that was SSTO depends on how you count the booster engines)

Matt Bille

  #5  
Old March 15th 06, 08:43 PM posted to sci.space.tech
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Default Single Stages That Could Go All The Way

Charles Talleyrand wrote:
I've read that there are stages of rockets that have actually flown
that had a high enough ISP and mass ratio they could have gone to
orbit if they did not need to carry a payload. In other words, if
someone had fired off the first stage of the Saturn 5, it could have
made orbit all by itself except it was carrying the rest of the rocket.

Is this true? Can someone offer some examples? And what practical
problems (like bringing along an aerodynamic shield for the nose) might
one encounter in real life.

Note, I'm not asking about hypothetical SSTO rockets, but real flown
stages.

-Charles Talleyrand


In order to calculate the delta-V of a rocket stage, you divide the
gross weight of the stage by the weight with all fuel expended, take
the natural log, and multiply by the exhaust velocity. If that stage
is commonly launched with boosters, then one must remember that the
liftoff thrust must exceed the GLOW.

Of the flown first stages over at www.astronautix.com, I seem to find
only one that exceeds the 9200 meters per second of deltaV that I find
as a common limit for reaching LEO.

The first stage of the Japanese H-2 rocket -
http://www.astronautix.com/lvs/h2.htm - combined a 12.1% structural
fraction with a high ISP (443 sec), and a 1.1:1 T/W ratio to achieve
about 9220 meters per second of total deltaV, the highest I have found
in their database.

The Atlas CCB - http://www.astronautix.com/stages/atlasccb.htm - has a
very low structural fraction when you subtract the interstage adapters,
but it only works out to 8910 meters/sec of total deltaV. I have seen
some studies that suggest that this would be enough, though. These
studies show that lower ISP LOX/Kerosene vehicles require about
300m/sec LESS deltaV to reach orbit. The G-loads on burnout for the
Atlas CCB would over 10G, even with a 50% throttle.

The Saturn V first stage has an even lower structural fraction than the
CCB, but the 10% lower ISP means that it won't have enough deltaV to
reach orbit unless you drop four of the engines on the way up.

P.S. Required deltaV is less if you launch from the equator. It is
possible that the Saturn V first stage and other marginal cases might
be adequate to reach LEO from a true equatorial launch.

 




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