Orbital ballet

Any practical plan to reach the Moon would involve rendezvous and docking in space. Rehearsing these manoeuvres was to be a key part of the later Gemini missions.

HISTORY FOCUS

23 August 1965

Gemini 5 practises a phantom rendezvous in orbit, after fuel-cell problems prevent rendezvous with its intended target.

25 October 1965

The planned launch of Gemini 6 is scrubbed after its Agena docking target fails to reach orbit.

4 December 1965

Gemini 7 successfully launches on a 14-day endurance mission for Jim Lovell and Frank Borman.

12 December 1965

The planned launch of Gemini 6 aborts due to an engine fault on ignition. Since the crew did not eject from the spacecraft, the launch can be rescheduled.

15 December 1965

Gemini 6A (previously Gemini 6) launches and makes a rendezvous with Gemini 7.

16 March 1966

Gemini 8 achieves the first successful space docking shortly after launch, but a malfunction brings the mission to a premature end.

HISTORY FOCUS

Simple fuel economics meant that the most direct route to the Moon - a launch directly from Earth of a spacecraft that could simply touch down in one piece on the Moon and carry enough fuel to blast off and return to Earth - was out of the question. NASA's mission planners came up with two practical alternatives (see p.117), but both would involve precision flying to bring together the parts of a lunar spacecraft in orbit.

Early attempts

Early tests of Gemini's flight controls showed how much there was to learn. Gemini 3 proved that the capsule could change its orbit, but Gemini 4's attempts to catch up with its own discarded upper stage met only with frustration - as the capsule fired its thrusters, instead of catching up with the target, White and McDivitt found that they drifted into a higher orbit (see panel, right). Gemini 5 released a small pod into a different orbit to use for target practice, but a fuel cell problem meant that the crew could not risk wasting energy to catch it. Fortunately Buzz Aldrin, a trainee astronaut and orbital mechanics expert, came up with a new test - a phantom rendezvous in which Gemini 5 flew to a precise point without burning excessive energy.

TECHNOLOGY

SWITCHING ORBITS

IN A SPIN

Shortly after Gemini 8 docked with its ATV (see p.106) the crew of David Scott (left) and Neil Armstrong faced a serious problem, as a jammed thruster set the joined spacecraft spinning rapidly. Separating from the ATV only made the problem worse, and Armstrong had no choice but to shut down the thruster system and fire the re-entry engines to stabilise the spacecraft. The plan worked, but it brought the spacecraft back to an emergency splashdown just 10 hours after launch.

Changing orbits in space is simply 1 gold craft a matter of firing engines to fires thrusters either slow down or speed up the spacecraft. In the example shown here, two spacecraft start out side by side in a circular orbit around the Earth. The gold craft briefly fires its thrusters, but instead of moving faster in its existing orbit, it is pushed into an elliptical orbit, with a higher apogee (the point in the orbit furthest from Earth). The further a spacecraft is from the object it is orbiting, the slower it moves, and this, combined with the greater distance it travels, causes the gold craft to lag further and further behind, even though both craft still have a common perigee (the point closest to Earth).

Dual flights

The next plan was to rendezvous with an unmanned Agena Target Vehicle or ATV (an adapted rocket stage) that had already been launched into orbit. This was to have been the mission of Gemini 6, but even as Walter Schirra and Thomas Stafford sat in their Titan rocket on 25 October 1965, ready to chase their target into orbit, the ATV launcher exploded and the mission had to be scrubbed.

2 gold craft starts to lag behind as it switches to ellipticol orbit

3 red craft maintains circular orbit

2 gold craft starts to lag behind as it switches to ellipticol orbit

3 red craft maintains circular orbit

4 gold craft's elliptical orbit now has higher apogee

SEEING IS BELIEVING

During their closest approach, Jim Lovell, aboard Gemini 7, asked, "How's the visibility?". "Pretty bad," replied Wolter Schirra on Gemini 6 A, "I can see through the window and see you fellows inside!"

MEETING IN SPACE

Schirra and Stafford took this photograph of Gemini 7 as their own Gemini 6A capsule flew towards the first fully controlled orbital rendezvous. Gemini 7 had already been in orbit for 11 days.

CLOSING IN

At their closest approach, the Gemini spacecraft were so close that the astronauts could communicate by holding handwritten signs up to the windows of their capsules, 260km (160 miles) above the Earth.

Frank Borman and Jim Lovell, whose Gemini 7 mission was intended largely as a two-week space-endurance test, now made an audacious suggestion - why not have Schirra and Stafford rendezvous with them instead? NASA officials took some persuading, but eventually Gemini 7 launched on 4 December, with a renamed Gemini 6A following 11 days later. Schirra skilfully steered his spacecraft to within 30cm (1ft) of the waiting target, and the astronauts waved to each other, but there was no way for them to dock.

The normal launch schedule resumed in March 1966, when Neil Armstrong and David Scott's Gemini 8 performed the first ever space docking with the ATV. However, the mission was short-lived, as the docked vessels developed a dangerous spin that brought the flight to an early end (see panel, opposite).

GEMINI 6A IN ORBIT

A head-on view of Gemini 6A from Gemini 7 reveals the "business end" of the spacecraft, the docking adopter that allowed a Gemini capsule to mate with an Agena ATV that could boost it into a higher orbit.

17 May 1966

Gemini 9's Agena ATV fails to reach orbit.

1 June 1966

The Augmented Target Docking Adapter (ATDA), a new target for Gemini 9, is launched.

3 June 1966

Gemini 9A launches to a rendezvous with the ATDA, but docking is not possible.

18 July 1966

Gemini 10 is launched and docks successfully with its ATV.

20 July 1966

Gemini 10 makes a second rendezvous, with the abandoned Gemini 8 ATV.

12 September 1966

Gemini 11 launches and docks successfully with its ATV, setting a new world altitude record.

15 November 1966

Gemini 12 successfully splashes down.

28 February 1966

The planned Gemini 9 crew, Elliott See and Charles Bassett, are killed when their T-38 jet crashes.

RIDING HIGH

Astronaut Dick Gordon of Gemini 11 straddles the Agena ATV, while attaching the tether that would later be used to generate the first artificial gravity in space.

ADAPTER IN ORBIT

The Augmented Target Docking Adapter (ATDA) designed for Gemini 9 floats high above the Earth, its shrouding still half-attoched. This unusual view of the device led to Thomas Stafford's memorable comment, likening it to an "angry alligator".

THWARTED PLANS

As Gemini 9A came in sight of the hastily launched ATDA docking target, Thomas Stafford exclaimed "Look at that moose!" The protective shroud was frustratingly close to coming free, but edging the Gemini capsule's nose into the open end was too risky.

28 February 1966

The planned Gemini 9 crew, Elliott See and Charles Bassett, are killed when their T-38 jet crashes.

17 May 1966

Gemini 9's Agena ATV fails to reach orbit.

1 June 1966

The Augmented Target Docking Adapter (ATDA), a new target for Gemini 9, is launched.

3 June 1966

Gemini 9A launches to a rendezvous with the ATDA, but docking is not possible.

18 July 1966

Gemini 10 is launched and docks successfully with its ATV.

20 July 1966

Gemini 10 makes a second rendezvous, with the abandoned Gemini 8 ATV.

12 September 1966

Gemini 11 launches and docks successfully with its ATV, setting a new world altitude record.

15 November 1966

Gemini 12 successfully splashes down.

Learning to fly

The final phase of the Gemini programme saw a series of increasingly ambitious flights, dockings, and EVAs as America's astronauts geared up for the coming Apollo missions.

Even before launch, Gemini 9 was cursed by bad luck - the original crew of Elliott See and Charles Bassett died in February 1966 when their plane crashed in fog while attempting to land at the McDonnell plant in St. Louis, Missouri, where their spacecraft was under construction. As a result, the backup crew of Thomas Stafford and Eugene Cernan took their place.

The mission plan involved a rendezvous with an Agena ATV, but as had happened before, the target vehicle failed to reach orbit. A replacement was built and launched in just two weeks, and the Gemini mission (renamed 9A to indicate the use of a backup crew) flew to meet it two days later, on 3 June. The rendezvous went perfectly, but the astronauts discovered that the shroud around the target vehicle had not separated properly, and so docking would be impossible. Nevertheless the mission continued, with the crew practising a variety of manoeuvres in orbit.

The capsule carried with it a prototype Astronaut Manoeuvring Unit (AMU), or rocket pack, to aid astronauts in orbit. The intention was for Cernan to test the device, but it had been mounted on the hull near the back of the spacecraft, and Cernan's efforts to reach it were hampered by a lack of handholds. When he did get there, he discovered that donning the AMU would mean severing his main tether to the cabin, and he would probably be unable to reattach it. In the end, an exhausted Cernan, his visor steamed up by his exertions, decided that it was too risky. He returned to the capsule after a 128-minute spacewalk, the mission incomplete but with many lessons learned.

Geminis 10 and 11

Fortunately, Cernan's misadventure was the last major setback for Gemini. Little more than a month later, Gemini 10, crewed by John Young and Michael Collins, achieved a very successful double rendezvous - docking first with their own ATV

RIDING HIGH

Astronaut Dick Gordon of Gemini 11 straddles the Agena ATV, while attaching the tether that would later be used to generate the first artificial gravity in space.

and then using its engines to boost their orbit for a close rendezvous with the ATV abandoned during Gemini 8. Collins was even able to spacewalk across to the dormant vehicle.

Gemini 11, launched on 12 September 1966, was also a success. Pete Conrad and Richard Gordon were able to dock with their booster just 85 minutes after launch, and Gordon made a spacewalk to attach a tether from the Gemini capsule to the Agena, before they propelled themselves to a new record altitude of 1,374km (854 miles). As they returned to a lower orbit, they undocked from the ATV so that the two spacecraft began to spin around their common centre of mass. The result was a weak form of artificial gravity for the two astronauts.

ADAPTER IN ORBIT

The Augmented Target Docking Adapter (ATDA) designed for Gemini 9 floats high above the Earth, its shrouding still half-attoched. This unusual view of the device led to Thomas Stafford's memorable comment, likening it to an "angry alligator".

Last hurrah

The final Gemini mission was the most ambitious of all, and fortunately a great success. After a series of delays caused by spacecraft glitches, Buzz Aldrin and Jim Lovell ascended to orbit on 11 November 1966. Their four-day mission was a dry run for many of the techniques needed for Apollo, and they practised docking and undocking the ATV, and manoeuvring with it attached. Plans to use it to boost them into a higher orbit had to be abandoned, however, because of concerns over the ATV's condition after launch. Perhaps the most important achievements of the mission were Aldrin's EVAs. Extra grips had been fitted to the capsule to help with weightless manoeuvres, and Aldrin was able to spend over two hours on the end of an umbilical tether, carrying out various tests and finally proving that an astronaut could perform useful work outside a spacecraft.

THWARTED PLANS

As Gemini 9A came in sight of the hastily launched ATDA docking target, Thomas Stafford exclaimed "Look at that moose!" The protective shroud was frustratingly close to coming free, but edging the Gemini capsule's nose into the open end was too risky.

"It looks like an angry alligator out here rotating around."

FLOATING FREE

During his second EVA, Aldrin floated free, tethered to his spacecraft by an umbilical line. Here, he is conducting experiments at a workstation attached to the ATV and taking photographs of star fields.

Gemini 9A astronaut Thomas Stafford describes the defective target vehicle, 3 June 1966

STAND-UP EXPERIMENTS

Gemini 12's first EVA lasted for just under two-and-a-half hours and was a stond-up - Buzz Aldrin stood up in the capsule's hatch and performed various experiments, as well as setting up ultraviolet and movie cameras.

PARTICLE COLLECTOR

Here Aldrin is retrieving a micrometeorite collector. The device was used to collect small particles drifting through Earth orbit. These were later analyzed for signs of any organisms capable of living in space.

omni directional antenna

23 August 1961

Ranger 1, an ill-fated engineering test for NASA's series of lunar crash-landers, fails to reach its intended orbit around the Earth.

26 January 1962

Ranger 3, the first of the Ranger probes intended for the Moon, is launched but misses its target completely.

31 July 1964

Ranger 7 becomes the first successful probe in the series, sending back pictures right up to its impact with the Moon.

2 June 1966

Surveyor 1 touches down in the Oceanus Procellarum - the first successful soft-landing on the Moon.

10 August 1966

Lunar Orbiter 1 is launched into orbit around the Moon, the first of five mostly successful orbiter probes that capture details on the lunar surface as small as 2m (6ft) across.

31 January 1968

Lunar Orbiter 5 crashes onto the Moon after a successful mission.

Surveying the Moon

To pave the way for Apollo, NASA embarked on an ambitious programme of lunar discovery. This involved three different series of spaceprobes - Rangers, Surveyors, and Lunar Orbiters.

When President Kennedy announced America's lunar ambitions in May 1961, the closest thing to a successful moonshot achieved by NASA had been Pioneer 4's relatively near miss in March 1959 (see p.52). The Moon still held many mysteries - and while some were scientific puzzles of interest mainly to astronomers, others might have a direct bearing on any expedition attempting to land there.

For example, were the Moon's plentiful craters volcanic or formed by impacts from space? If they were volcanic, would there still be seismic activity on the Moon? If they were caused by impacts, then would the surface be stable, or so badly pulverized that it could not support the weight of a spacecraft?

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