Author Topic: Saturn V modifications needed for maximum discretionary LEO payload?  (Read 15447 times)

Offline joema

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Takalok - 1/4/2008  8:56 PM...
Apparently this tread's thoughts that the fuel in the S-IVB would reduce LEO is correct.  However, it seems the best result for LEO is just eliminate the third stage altogether...
We can do a few simple calculations on this:

SA-512 (Apollo 17) total vehicle mass at FIRST SIVB cutoff was 140,893 kg. Total vehicle mass at SECOND SIVB cutoff was 65,664 kg. The difference is mostly propellant mass expended during the TLI burn, or 140,893-65,664 = 75,229 kg.

That implies for a non-lunar LEO mission, the orbital payload could be increased by roughly this amount. The Apollo spacecraft mass totaled about 48,609 kg. Thus the theoretical useful LEO payload would have been roughly 48,609 kg + 75,229 kg = 123,838 kg, minus any need SIVB structural reinforcement to carry the increased mass.

Compare to the SA-513 Skylab mission. Orbital workshop mass: 88,474 kg. SII dry weight: 36,697 kg, SII/OWS interstage: 3453 kg, payload shroud 11,630 kg. This totals 140,254 kg.

The stated orbital mass of entire SII/workshop vehicle is 147,531 kg, so don't know where the missing 7,000+ kg goes.

But while SA-513 (Skylab) had more mass in LEO, SA-512 (Apollo 17) had more functional, useful mass. Both partially-fueled SIVB and Apollo stack were functional. By contrast the expended SII stage on Skylab was inert.

To me this indicates a slightly-modified three-stage Saturn V with a partially-fueled SIVB could have orbited more useful payload than the two-stage version used on Skylab.

Online MKremer

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Don't forget to figure in the propellent needed to achieve the final orbit height for your extra mass - the moon missions only needed to get to a very minimal orbit prior to TLI.

Offline Jim

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joema - 1/4/2008  11:17 PM

To me this indicates a slightly-modified three-stage Saturn V with a partially-fueled SIVB could have orbited more useful payload than the two-stage version used on Skylab.

You can't make that conclusion.  
1.  Skylab was in a 50 degree orbit, which requires more performance
2.  Skylab was in a higher orbit, which requires more performance.
3.   No documentation shows that Skylab maxed the Saturn V's capabilitys.  Need to know the performance reserve.  
4.  partially fueling stages is not always viable
5.  Saturn V payload planner's guide says 261k lbs (118k kg)

Offline hmh33

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Also, volume is often the limiting factor for a payload, rather than mass.  Volume is limited by the height of the VAB, so 2-stage INT-21 can carry much more volume on top than a 3-stage vehicle before hitting the ceiling.

Offline Generic Username

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nacnud - 1/4/2008  1:39 PM
I asked on another thread but no one answered, was there ever a study for a one F1 engine Saturn 1B?

The H-1 engines in the Saturn Ib worked perfectly well. Making an F-1 version o the Saturn Ib would have meant major changes to the plumbing and aft structure, would have likely reduced rliability (no engine-out), would have made the vehicle longer (possible launch pad issues) and would have simply cost a lot of money.

It's often a lot easier to simply design from scratch than do a major redesign of flying hardware, especially when the gain isn't that great.
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Offline Jorge

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Generic Username - 3/4/2008  10:03 AM

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nacnud - 1/4/2008  1:39 PM
I asked on another thread but no one answered, was there ever a study for a one F1 engine Saturn 1B?

The H-1 engines in the Saturn Ib worked perfectly well. Making an F-1 version o the Saturn Ib would have meant major changes to the plumbing and aft structure, would have likely reduced rliability (no engine-out), would have made the vehicle longer (possible launch pad issues) and would have simply cost a lot of money.

It's often a lot easier to simply design from scratch than do a major redesign of flying hardware, especially when the gain isn't that great.

I suspect that, if this option had been pursued, it would be a clean-sheet replacement for the entire S-IB stage and not just the engines. It was an opportunity to eliminate the clustered tanks.

All moot, of course...
JRF

Offline Takalok

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nacnud - 1/4/2008  1:39 PM
I asked on another thread but no one answered, was there ever a study for a one F1 engine Saturn 1B?

F-1 configurations were studied in the NASA report Final Report - Studies of Improved Saturn V Vehicles and Intermediate Payload Vehicles.  The smallest configuration was the Saturn INT-20 consisting of 3 F-1 motors in the S-IC first stage with the S-IVB (third stage).  No middle stage.  The LEO of this configuration was 60,500 kg.

You can find a PDF of the report and a nice descriptions of the INT-20 at wikipedia here:
http://en.wikipedia.org/wiki/Saturn_INT-20
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Offline jeff.findley

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The thing I find interesting is that the INT-21 vehicle had 6 different proposed configurations based on how many F-1 and J-2 engines were used.  This is very similar to how the Direct/Jupiter launch vehicles are being designed.  You use a common design and eliminate engines to get lower cost vehicles for lower payloads.

Offline wingod

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mike robel - 1/4/2008  4:12 PM

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nacnud - 1/4/2008  3:39 PM
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Takalok - 1/4/2008  5:57 PMImagine - 410 feet tall with a 480 ton payload.  Hard to wrap my head around that.
To put that in perspective that is a one launch ISS! If only...I asked on another thread but no one answered, was there ever a study for a one F1 engine Saturn 1B?
I have never found one.  It almost boggles my imagination that noone ever did it.  I did make a model of one that is probably buried in the NASA model building thread.

At MSFC in building 4203 I found a model of a single F1A vehicle.  This was supposed to be a commercial type system.  I never found any written info on it.



Offline Proponent

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wingod - 24/4/2008  3:41 AM
At MSFC in building 4203 I found a model of a single F1A vehicle.  This was supposed to be a commercial type system.  I never found any written info on it.

Very interesting.  Do you recall about what size the vehicle appeared to be, i.e., was it about the same scale as the Saturn IB, was the diameter likely 260" (same as S-IVB)?  Any hints as two what would have been used for an upper stage?

Offline spacediver

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Regarding a replacement launcher for the Saturn 1B:

If they'd ever had decided to build that monster SAT-V-23(L) with its 6,6m liquid strap on boosters I'm sure that sooner or later someone woud have come up with the idea to combine one of these boosters with a standard S-IVB upper stage.

The result would have been a replacement for the Saturn 1B with additional payload (or SM propellant) capability for all manned LEO missions.

Just a bit "what if" brainstorming...

Spacediver

Offline Archibald

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---wingod - 24/4/2008 3:41 AM
At MSFC in building 4203 I found a model of a single F1A vehicle. This was supposed to be a commercial type system. I never found any written info on it. ---

Yep they intended to replace Saturn IB first stage by every means - single solids, two solids, S-II only (Saturn II) and son on-
I'm quite surprise, too, that they never thought about the F-1.
1 F-1 = 8*H-1  using the same propellants.
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Offline Steve G

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I always assumed that you would have needed a modified F1 with a throttle.  Without one, would there not have been excessive G forces at the end of the first stage burn?  Had there been no shuttle, and an improved (i.e. 5 man advanced Apollo) semi reusable capsule, one would have expected a Saturn 1C powered by a throtlable F1-A.  But 30 years later, this is, of course, pointless speculation.

Offline Takalok

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Steve G - 28/4/2008  1:32 PM

I always assumed that you would have needed a modified F1 with a throttle.  Without one, would there not have been excessive G forces at the end of the first stage burn?  Had there been no shuttle, and an improved (i.e. 5 man advanced Apollo) semi reusable capsule, one would have expected a Saturn 1C powered by a throtlable F1-A.  But 30 years later, this is, of course, pointless speculation.

The F-1A could throttle, but on the Saturn V, to control thrust they just shut down the center engine about 30 seconds before shutting down the other four (first stage).
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