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I read about the Skylab 1 mission in which SA-513 was used to lob the Skylab OWS into orbit. One source (http://forum.nasaspaceflight.com/index.php?topic=12519.20) gave some payload masses:

  • Total mass to LEO = 147,531kg
  • OWS mass = 88,474kg
  • S-II dry mass = 36,697kg
  • S-II/OWS interstage = 3453kg
  • Payload shroud = 11,630kg

The extra 7,000+ kg is redisual S-II propellant, and also the S-IC/S-II interstage that failed to separate after being damaged by debris from the OWS.

Excluding the S-II and its roughly 3t of propellant, but including the 4.1t S-IC/S-II interstage, the potential for usable payload was between 107t and 108t.

This payload was delivered to 50 degrees inclination at 434km in altitude. So, what could it have thrown to 185km and 28.5 degrees? Studies (From 1965, I believe) on the very similar Saturn INT-21 concept give that launcher a maximum payload of 115.7t (not including S-II) to 185km and 34.5 degrees. The date of those studies means that this may not factor in late-model weight savings and engine upratings made to SA-513, which went up in 1973. Could it have lifted more than 115.7t?

Some other sources give the Skylab OWS mass as being 75,000kg or even around 77t. I'm not sure of what figures are best.

Also, how tall was the Skylab/Saturn V combo anyway? I've found 333.7ft, 341.0ft and 343.8ft, but can't verify any of them.

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    $\begingroup$ I don't want to give this as an answer because I'm not a professional, but I've been working on a launch simulation tool, and in it I can get 127000 kg inert payload into orbit on a late-Apollo-spec, two-stage, Saturn V. Final orbit is 181km x 221km at 28.5º (I'm still fine tuning my orbital insertion guidance). The first-stage F-1 engines are producing 6878kN each, approximately equal to Apollo 15. I can't guarantee accuracy of my sim but when properly configured it gives similar results to Braeunig's Saturn V sim, which in turn tracks the actual Apollo 11 numbers well. $\endgroup$ – Russell Borogove Apr 5 '16 at 14:43
  • $\begingroup$ Hey, Russell! Well, that seems to show definite improvement in capability of the later Saturns. The 127,000kg figure you've achieved doesn't include the spent S-II stage, does it? Just out of curiosity, what was the mass of the stage and its residual propellant? No problem if you didn't record that. I have checked out Braeunig's Apollo 11 simulation, and I'd really like to run some data through it myself. Incredible detail! I just can't help wondering what the upper limits of the final Saturn Vs would have been. $\endgroup$ – Alastair Haslam Apr 6 '16 at 7:51
  • $\begingroup$ Come to think of it, would it be possible for me to send some data over to you so you can run it through your sim? If you've been getting results close to Braeunig's, that's pretty sweet! As of yet I'm not signed up completely, but I might as well do that... $\endgroup$ – Alastair Haslam Apr 6 '16 at 7:56
  • $\begingroup$ 127t payload after S-II depletion and separation -- since I was aiming for 185km periapsis and didn't quite get there, my sim used all the propellant available. Dry mass of the S-II is about 40t, and since I'm not modeling the stage separation in any detail, the stage is in the same orbit as the payload if you're thinking about a "wet workshop" station. You can mail me at (first name) @ (last name) .org if you have more things you want me to sim. $\endgroup$ – Russell Borogove Apr 6 '16 at 13:36
  • $\begingroup$ Aside: I was double-checking to make sure I was using the right stats on the first-stage engines, and it turns out the late-model F-1 engines used on Apollo 15-17 yielded barely any more thrust than the early ones -- the rated values changed more than the actual rocket performance. The average thrust of early (A9-A14) engines was 6720kN, the average of late engines was 6745kN (0.37% differrence). Individual engines on a single launcher usually varied by more than that! Incorporating the more-accurate engine stats, I'm downgrading my payload estimate for INT-21 from 127t to 126t. $\endgroup$ – Russell Borogove Apr 8 '16 at 14:39

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