Gemini 6A


Gemini 6A

Infobox Space mission
mission_name = Gemini 6A
spacecraft_name = Gemini 6A
booster = Titan II #62-12561
insignia = Ge06Patch emb.png insignia_size = 162px
sign = Gemini 6A
crew_members = 2
launch_pad = LC-19 (CCAF)
launch = December 15, 1965, 13:37:26 UTC
landing = December 16, 1965, 15:28:50 UTC coord|23|35|N|67|50|W
duration = 1d/01:51:24
orbits = 16
apogee = convert|259.4|km|nmi|lk=on
perigee = convert|161|km|nmi
period = 88.7 min.
inclination = 28.97°
distance = convert|694415|km|mi|lk=on
mass = convert|3546|kg|lb|lk=on
crew_photo = S65-56151.jpg
crew_caption = (L-R) Stafford, Schirra
previous =
next =

Gemini 6A (officially Gemini VI-A) was a 1965 manned spaceflight in NASA's Gemini program. It was the 5th manned Gemini flight, the 13th manned American flight and the 21st spaceflight of all time (includes X-15 flights over 100 km -- 62 miles.). It was the last U.S. spacecraft to be flown using batteries as the primary power source (except for the Apollo Lunar Module, which used batteries, but was augmented by the fuel cells on the Apollo Command Module while docked). All remaining Gemini flights used fuel cells.

Crew

Number in parentheses indicates number of spaceflights by each individual prior to and including this mission.
* Walter M. Schirra (2) - Command Pilot
* Thomas P. Stafford (1) - Pilot

Backup crew

* Virgil I. Grissom (2) - Command Pilot
* John W. Young (1) - Pilot

Mission parameters

* Mass: 3,546 kg, 7800 lbs.
* Perigee: 161 km, 100 miles
* Apogee: 259.4 km, 161 miles
* Inclination: 28.97°
* Period: 88.7 min


=Stationkeeping with GT-7=

* Start: December 15, 1965 19:33 UTC
* End: December 16, 1965 00:52 UTC

ee also

* Splashdown
* Agena Target Vehicle

Objectives

Gemini 6 was originally intended to be the first mission to dock with an Agena Target Vehicle. However, after a failure in the Agena target 6 minutes after its launch (when the crew of Gemini 6 was already sitting in their capsule waiting for their launch), the mission was canceled. Reviewing the situation, NASA decided to substitute an alternate mission: a meeting in space of two Gemini spacecraft. The new mission would be known as Gemini 6A, and would launch eight days after the launch of Frank Borman and Jim Lovell's Gemini 7. Schirra and Stafford tried to join them, but their Titan 2 launcher shut down on the pad (the cool-headed Schirra did not eject, even though the countdown clock had started ticking-he felt no motion, and trusted his senses). Three days later, Gemini 6A made it into orbit. Using guidance from the computer as well as his own piloting, Schirra performed the space rendezvous with the companion spacecraft in orbit on the afternoon of December 15. Once in formation, the two Gemini capsules flew around each other, coming within a foot, 0.3 meters, of each other but never touching. The two spacecraft stayed in close proximity for five hours. One of Gemini's primary goals—orbital rendezvous—had been achieved.


Flight

First launch attempt

The first launch attempt of Gemini 6A was on December 12. All went well right up to ignition--in fact the engines did ignite, but then a plug fell out of the bottom of the rocket, starting the onboard computer. This was not meant to happen until the rocket had actually lifted off, and the onboard computer detected that there was no upwards motion, causing it to abort the launch. At this point mission rules dictated that the crew should eject from the spacecraft, as the rocket would explode on impact with the pad if its trajectory was off by even an inch (2.54 cm).

Schirra elected not to eject as neither he nor Stafford had detected any upwards motion, and the ejection seats were seen as a last resort. In an early test of the system involving a dummy the hatch had failed to blow off and the dummy's head was rammed into the side of the spacecraft. Also all ejection seats cause compression of the spine and these were designed to send the astronauts a couple of hundred metres away from an exploding rocket.

The Martin and Air Force teams who erected and tested the rocket found that some plugs on the rocket were able to pull out more easily than others. They replaced them with the ones that were harder to pull out and on future missions, and a safety wire was added to make sure that the rocket had lifted off.

However, another problem was found as the engineers examined the thrust versus time graph. They found that the thrust rose nominally but started to get lower before the plug had fallen out. Through the night, engineers examined the rocket engine piece by piece until they found that a plastic cover had been left in the gas generator port. With this problem solved the rocket and spacecraft were recycled for a launch 72 hours after the first attempt.

Rendezvous

The third attempt to launch Gemini Spacecraft Number 6 was successful on December 15. All went well through launch and ascent and the crew entered a 161 by 259 kilometers orbit, or as per the actual flight specifications, a 100 by 161 mile orbit.

The plan called for the rendezvous to take place on the fourth orbit of Gemini 6A. Their first burn came 94 minutes after launch when they increased their speed by 5 meters per second, 16 1/2 feet per second. Due to their lower orbit they were gaining on Gemini 7 and were only 730 miles, or 1,175 kilometers behind. The next burn was at 2 hours and 18 minutes when Gemini 6A made a phase adjustment to put them on the same orbital inclination as Gemini 7. They now only trailed by 483 kilometers, 300 miles.

The radar on Gemini 6A first made contact with Gemini 7 at 3 hours and 15 minutes when they were 434 kilometers, 270 miles away. A third burn put them into a 168 x 170 mile (270 by 274 kilometer) orbit. As they slowly gained, Schirra put Gemini 6A's computer in charge of the rendezvous. At 5 hours and 4 minutes he saw a bright star that he thought was Sirius, but this was in fact Gemini 7.

After several more burns the two spacecraft were only 130 feet, 40 meters apart. The burns had only used 112 lbs., 51 kilograms of fuel on Gemini 6A, giving plenty of fuel for some fly arounds. During the next 270 minutes the crews moved as close as 1 foot to 295 feet, 30 centimetres to 90 meters, talking over the radio. At one stage the spacecraft were stationkeeping so well that neither crew had to make any burns for 20 minutes.

As the sleep periods approached Gemini 6A made a separation burn and slowly drifted out to 10 miles, 16 kilometers. This ensured that there wouldn't be any accidental collisions in the night. But before everyone went to sleep, the crew of Gemini 6A had a surprise for everyone.

Gemini VII, this is Gemini VI. We have an object, looks like a satellite going from north to south, probably in polar orbit…. Looks like he might be going to reenter soon. Stand by one…. You just might let me to pick up that thing…. I see a command module and eight smaller modules in front. The pilot of the command module is wearing a red suit.

At that point, the sound of "Jingle Bells" was heard played on an 8-hole harmonica and a handful of small bells. The Smithsonian claims these were the first musical instruments played in space [Smithsonian magazine, December 2005] and keeps the instruments on display.

Reentry

Gemini 6A reentered the next day landing within 18 km of the planned site, the first truly accurate reentry. It was also the first to be televised live, through a satellite linkup from the recovery aircraft carrier USS "Wasp".

The Gemini 7 & 6A missions were supported by the following U.S. Department of Defense resources: in original units: 10,125 personnel, 125 aircraft and 16 ships; metric: 10,125 personnel, 125 aircraft and 16 ships.

Insignia

Walter Schirra explained the patch in his book All We Did Was Fly to the Moon:cquote|The Gemini 6 patch is hexagonal in shape, reflecting the mission number; and the spacecraft trajectory also traces out the number "6". The Gemini 6 spacecraft is shown superimposed on the "twin stars" Castor and Pollux, for "Gemini".

I designed the patch to locate in the sixth hour of celestial right ascension. This was the predicted celestial area where the rendezvous should occur (in the constellation Orion). It finally did occur there.

The original patch had called the flight G-T-A-6 (for Gemini-Titan-Agena) and showed the Gemini craft chasing an Agena. It was changed when the mission was altered.

Capsule location

The capsule is currently on display at the Oklahoma History Center in Oklahoma City, after having been on display at the Omniplex Science Museum elsewhere in the city. It is on a long term loan from the Smithsonian Institution. Before coming to Oklahoma, the capsule was displayed at the St. Louis Science Center in St. Louis, Missouri.

References

External links

* [http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19790076749_1979076749.pdf Gemini 6 Mission Report (PDF) - October 1965 cancelled mission]
* [http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19750069069_1975069069.pdf Gemini 6/Agena target vehicle 5002 systems test evaluation (PDF) December 1965]
* [http://www.hq.nasa.gov/office/pao/History/SP-4203/cover.htm On The Shoulders of Titans: A History of Project Gemini]
* [http://www.genedorr.com/patches/Intro.html Spaceflight Mission Patches]
*http://www.collectspace.com/news/news-092703a.html


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