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On 3 November 1966 a modified Titan IIC launched from LC-40 in Cape Canaveral. This launch would be the only launch as part of the Manned Orbiting Laboratory program. Designated OPS 0855 the vehicle consisted of an earlier flown Gemini capsule, OV4-1 and OV1-6. As the mission profile reads:

OPS 0855 was the primary payload of Titan IIIC 3C-9, The Gemini B prototype capsule, known as Gemini SC-2, was flown on the same rocket, and was released onto a suborbital trajectory during launch. The adaptor connecting the Gemini spacecraft to OPS 0855 contained three additional spacecraft, two OV4-1 satellites, and OV1-6. These were released into low Earth orbit.

And another source reads

The satellite was spin stabilized after Transtage shutdown. On the upper end, a Gemini B capsule was mounted during launch and released on a suborbital trajectory. Also inside the Gemini B adapter were three small satellites: OV1 6, OV4 1R and OV4 1T. OV4-3 worked for 30 days (75 days were planned).

So first the Gemini capsule was released and then the second stage would burn continuing going into a stable orbit around the Earth. How did they make sure that the Gemini capsule had enough distance from the second stage before they lighted its engines and prevent it into crashing one and another? Did the Gemini capsule used it's own propulstion system to target itself away from the Transtage?

Also any other general information about this unique mission is welcomed

OV4-3

Picture of The OV4-3 (Orbiting Vehicle 4-3) and the Titan Transtage

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    $\begingroup$ If the MOL had ever been flown, the astronauts would have accessed the lab by crawling through a hatch cut in the Gemini heat shield. One of the objectives on this mission was to test the integrity of the hatch. When the capsule was recovered, it was found that the hatch had been welded shut by the re-entry heating but it had not affected the heat shield as a whole and the concept was valid. $\endgroup$
    – GordonD
    Nov 3, 2021 at 16:34
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    $\begingroup$ Great question! $\endgroup$ Nov 4, 2021 at 0:27

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Thanks for a really interesting question - I'd looked into the MOL test launch a couple of times, but never considered this.

The answer is found in SSSLV-5 NO. 9 POST FIRING FLIGHT TEST REPORT (FINAL EVALUATION REPORT) AND MOL-EFT FINAL FLIGHT TEST REPORT paragraph 3.1.3.7 Gemini Separation

I expected to see small solid motors push the capsule off - but no. The opposite happened. It happened at a time when the third stage was not firing, and ...

The Gemini separation maneuver involved decelerating the transtage - MOL - Adapter (TMA) away from Gemini by the use of 5 retro-rockets, and pitching the TMA nose up by use of the asymmetric arrangement of the retro-rockets and pitch-roll mixing of the ACS rockets. The proper separation rates were achieved, but the TMA pitched nose-down during retro-rocket firing instead of nose-up.

ACS = Attitude Control System

Diagram from the document showing the location of the retro-rockets (annotations mine)

schematic drawing of the upper stage and payloads of the MOL test vehicle with the retro-rockets annotated.

Here is a summary of the timeline. The document is full of exquisite detail if you want more. Time is in seconds, rounded off by me.

  • 0 Liftoff on SRBs
  • 110 Stage I engine ignition
  • 122 SRB separation
  • 258 Stage I engine shutdown / Stage II engine start / separation
  • 459 Stage II engine shutdown
  • 469 Stage II / III separation
  • 472 Stage III Burn 1 ignition
  • 779 Stage III Burn 1 shutdown
  • 810 Gemini separation
  • 813 Stage III retro-thrust
  • 844 Stage III Burn 2 ignition
  • 886 Stage III Burn 2 shutdown
  • 3182 Stage III Burn 3 ignition
  • 3188 Stage III Burn 3 shutdown
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    $\begingroup$ Thank you very much for the great answer. Never thought I would get a great explanation on this unique mission. $\endgroup$ Nov 9, 2021 at 8:23

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