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The Launchbox, Pod 13: The Near Misses of Gemini (Part 1)

By Andy Cooke

Following the successful completion of the Mercury programme (and NASA managing to sidestep a series of potential disasters), the next step was Gemini. Originally known as “Mercury Mark II”.

Mercury proved that NASA could send astronauts into space and keep them alive, do simple manoeuvres, and get them back fairly reliably. That was it. Given that JFK had signed them up to get a man all the way to the Moon and safely back in (checks watch) another six and a half years, they’d need to step it up a bit.

They’d got out of the atmosphere and to an orbital altitude of 285 kilometers. The longest single flight had been just over 34 hours, and the spacecraft had been practically falling apart at the end of it.

They needed to get 400,000 kilometres away to the Moon. And land on it. And come back. Taking definitely over a week to do it. And in most scenarios, this would involve spacecraft rendezvousing in space (at orbital velocities of around 8 kilometres per second with characteristics of flight that were totally non-intuitive and like nothing else ever experienced), then actually physically docking. Using full on orbital manoeuvring (not just the attitude adjustments and tiny orbital changes of Mercury)It would involve astronauts leaving the vehicle (otherwise it would be a bit of a damp squib when people landed on the Moon and stayed inside for a few minutes before heading home). New ways of navigating and communicating.

So they decided they needed a learning project to learn how to do these. Including a new multi-person spacecraft (two people) and a more powerful booster to put it into orbit, and Gemini came about.

So far, so good. There was, though, a lot to learn.

Gemini Escape System

Gemini ejection sequence of events. Image: NASA

With any spacecraft and booster, the escape system is crucial – especially with an experimental programme. Mercury used an “escape rocket” – a reliable small solid rocket on the nose which, when ignited, would yank the capsule off of the rocket and clear of the explosion (because you’d only be triggering your escape system to get away from an explosion – usually on the launch pad).

Gemini didn’t use this. The launch tower was heavy for a start (although it could get jettisoned part way into orbit). In addition, there were plans to have Gemini glide back to land – which could go wrong, and a launch tower wouldn’t be helpful at that stage of the game. Given these issues, and that the hypergolic fuel and oxidizer in the Titan rocket chosen should cause a far less vigorous explosion if the launch went wrong (albeit while producing a very toxic cloud of gas afterwards), the decision was made to go with ejection seats instead.

With a note to deactivate them after a short while into flight – after reaching 45,000 feet. Hopefully the booster wouldn’t go bang after that. At this point, the astronauts would stow the ejector handles. Pulling them accidentally at any point in the mission would be detrimental to mission success.

The astronauts weren’t totally happy with the method. John Young and Gus Grissom (who were the crew for the first manned Gemini mission) witnessed a test of the ejection seat. The hatch failed to open. However, the seat and the test dummy still got out through it, such was the force of the ejection. Young reportedly turned to Grissom and said “That’s a hell of a headache, but a short one.”

The early Geminis

Astronaut Ed White spacewalking over the Gulf of Mexico in Gemini 4. The astronauts had difficulty closing and latching the hatch after he returned to the spacecraft. Image: NASA

The Gemini missions went off quite closely according to plans – in comparison with Mercury. Gemini 1 and 2 were unmanned tests and were successful (Trivia note: Gemini 2, after its suborbital lob to test the heatshield system, was reflown (again unmanned) as a test for the later-cancelled Manned Orbital Laboratory. Other than the X-15 rocket plane, it was the only spacecraft to make more than one flight into space until the Space Shuttle).

Gemini 3 was successful with no major alarms. After Grissom (mindful of his near sinking in Liberty Bell 7) decided to call the spacecraft Molly Brown (after “The Unsinkable Molly Brown”), NASA had a sense of humour failure and banned naming spacecraft again until needing to differentiate between multiple spacecraft in flight on Apollo 9-Apollo 17.

Gemini 4 saw the first American spacewalk – by Ed White. There was some difficulty in both opening the hatch and then, more worryingly, in closing it after White got back in – which would have been catastrophic on re-entry - but this was successfully done (albeit the astronauts then understandably chose to not open it again to throw out the now-redundant EVA equipment). The only real What-If here is what if they’d failed to close the hatch? (If they’d failed to open it in the first place, there would just have been one extra flight). Gemini 4 also set a new record for longest American flight – over 4 days.

Gemini 5 went off with no near-disasters, doubling the on-orbit duration of Gemini 4 and taking the overall record from the Soviets for the first time. No real major “what if’s” from this one

Gemini 6 and 7

The plan: rendezvous in space. Image: NASA

For the first time, the US were going to attempt a proper on-orbit rendezvous between two manned spacecraft: Gemini 6 and Gemini 7. This was already a change to the plan – Gemini 6 was originally supposed to rendezvous – and dock – with an unmanned “Agena Target Vehicle”, to be launched separately.

Unfortunately, while astronauts Wally Schirra and Tom Stafford waited on the pad on board Gemini 6, poised to launch, the Agena Target Vehicle disintegrated. Probably due to its Atlas booster exploding. A quick review changed the mission to one of rendezvous with Gemini 7 – which would now launch first. They couldn't dock - but the orbital shenanigans needed to successfully rendezvous and hold position (the earlier Soviet "rendezvous" between Vostok 3 and 4 in 1962 had not been a rendezvous at all - they were simply launched onto trajectories that came close to each other and whizzed on by).

Gemini 7 was launched with no problems onto an epic two-week long-duration mission. Eleven days into their mission, they had a great vantage point to observe the delayed Gemini 6 launch, as they were literally flying directly overhead at launch time.

They saw a brief puff of smoke and nothing more.

Gemini 6 at T+1 second. It got no further - this time. Image: NASA

On Gemini 6, the countdown had expired, the engines ignited – and, just over a second later, cut off. Mission parameters dictated an immediate ejection – the booster lifting off and settling back would certainly explode, and the astronauts really needed to be at least 800 feet away from the explosion.

Schirra did not pull the ejection handle. Stafford was in full agreement. They decided that there had been no movement, and that ejection would very probably kill them. Stafford said, years later, if they had, they, “would have been two Roman candles going out, because we were 15 or 16 psi, pure oxygen, soaking in that for an hour and a half." … “it would have burned the suits. Everything was soaked in oxygen. So thank God. That was another thing: NASA never tested it under the conditions that they would have had if they would have had to eject. They did have some tests at China Lake where they had a simulated mock-up of Gemini capsule, but what they did is fill it full of nitrogen. They didn't have it filled full of oxygen in the sled test they had."

A successful rendezvous - Gemini 6 and Gemini 7. Image: NASA

The Titan did not explode. Three days later, it was successfully launched and they rendezvoused with the now rather tired Gemini 7 crew.

But what if they had ejected? Would they have survived? Would Stafford’s fears have been realized? And what if the booster had moved and then exploded – without them ejecting?

What If

The biggest What Ifs of the first five Gemini missions are:

  • What if the hatch never closed on Gemini 4?

  • What if the astronauts on Gemini 6 had ejected after all?

  • What if they hadn't ejected and the booster had exploded after all?

There are lesser What Ifs, of course. What If the hatch hadn't been able to be opened in the first place on Gemini 4? What if the Agena Target Vessel had got to orbit and Gemini 6 been able to try its original mission (would the same issue have happened on the booster)? But these three have the greatest potential to derail the entire programme.

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Andy Cooke has written the sci-fi Endeavour trilogy (The End and Afterwards, Diamond in the Dark, Beyond the Sunset) and the political alternate history Lectern books (The Fourth Lectern, The Fifth Lectern), published by SLP.