The Spacewalks That Never Were: Gemini Extravehicular Planning Group (1965) (2)
Gemini IX would see the first use of the U.S. Air Force Modular Maneuvering Unit (MMU), a hydrogen-peroxide-fueled "rocket pack" that would reach orbit stowed in the Adapter Section. The Gemini IX EVA astronaut would back up to the MMU, connect his ELSS to its integral oxygen supply, then grip t-shaped hand controllers and fly away from Gemini IX. The MMU's hot-gas thrusters would require that the astronaut's G4C suit be modified to include protective multilayer metal-fabric and foil leg coverings.
The GEPG noted that MMU development was proceeding to schedule, but added that NASA and the Air Force had yet to agree on the MMU's purpose or on whether it could fly without a safety tether linking it to the Gemini spacecraft. These questions were, it added, "beyond the scope of the present planning study."
The Gemini X EVA astronaut's tasks would focus on his spacecraft and the space environment. He would release "dense smoke" ahead of Gemini X and film its flow over the spacecraft's surfaces, photograph Gemini thrusters firing during day and night, gauge static charge on Gemini X and its GATV using a hand-held electroscope, measure hull temperature, and collect samples of contaminants (for example, the greasy contaminant that tended to cloud Gemini cockpit windows).
The GEPG also recommended two tether dynamics experiments for Gemini X. The spacewalker would simulate an untethered EVA using a "long slack tether," then would link his spacecraft and an inoperative Agena using a "towline." After the EVA, Gemini X would attempt to pull the Agena through space in an "evaluation of dynamics of orbital tow."
Gemini XI would see a dramatic increase in EVA complexity. The spacecraft would intercept the 10.5-ton Pegasus 3 satellite, which was due to be launched into low-Earth orbit on a Saturn I rocket soon after the GEPG submitted its report. Like its predecessors, Pegasus 3 was designed to assess the likelihood that spacecraft in low-Earth orbit would suffer meteoroid impact damage. To do this, it unfolded a pair of 4.3-meter-wide-by-29-meter-long "wings" containing a total of 400 meteoroid-detection panels.
Artist concept of Pegasus satellite. Image credit: NASAThe GEPG reported that discussions with NASA Headquarters and NASA Marshall Space Flight Center had already led to Pegasus 3 modifications for Gemini rendezvous and EVA mission. Pegasus 1, launched 16 February 1965, had achieved an elliptical 510-by-726-kilometer orbit, while Pegasus 2, launched 25 May 1965, had entered a 502-by-740-kilometer orbit. When launched on 30 July 1965, Pegasus 3 entered a near-circular 535-by-567-kilometer orbit. This made it a more readily accessible rendezvous target for Gemini spacecraft.
In addition, sixteen of Pegasus 3's meteoroid-detection panels had been replaced with removable aluminum meteoroid-capture panels and panels containing thermal control test surfaces. After rendezvous with the giant satellite, the Gemini XI spacewalker would use an HHMU to jet over and remove the panels for return to Earth. The GEPG stated that "[d]etermination of the method of accomplishing this task. . .must still be accomplished."
Gemini XII would see the second flight of the MMU rocket pack. If the Gemini IX MMU test was performed using a tether, then consideration would be given to untethered flight during Gemini XII. The mission would also rendezvous with the 2300-kilogram Missile Defense Alarm System (MIDAS) II satellite, which had failed two days after it reached orbit on 24 May 1960. The EVA astronaut would inspect and photograph MIDAS II in an effort to determine the cause of its failure.
The GEPG suggested alternate missions for Gemini XI and XII that would see one or both missions meet up with Apollo spacecraft in orbit. A Gemini might, for example, rendezvous with the SA-204 Apollo CSM, which in July 1965 was scheduled to be launched in September 1966. SA-204 was planned to be the first manned Apollo CSM flight, but it would be flown unmanned if either of the two suborbital test flights scheduled to precede it failed. The EVA astronaut would transfer to and enter the unmanned CSM, check out its systems, and return to the Gemini.
If Gemini XII were postponed until February 1967, then it might rendezvous with the unmanned LM planned for launch on mission SA-206. The spacewalker would enter the spindly LM, check out its systems, and jet back to Gemini XII.
NASA accepted many of the GEPG's recommendations. As it began preparations to implement them, it conducted Gemini missions V, VI, and VII. After a rough start, Gemini V (Gordon Cooper and Charles Conrad, 21-29 August 1965) successfully conducted an improvised "phantom rendezvous" with a point in space and remained in orbit for eight days. Gemini VII (Frank Borman and James Lovell, 4-18 December 1965) stayed aloft for 14 days, demonstrating that astronauts could survive in space long enough to reach and return from the moon.
Gemini VI (Wally Schirra and Tom Stafford, 15-16 December 1965) had been scheduled to launch on 25 October 1965, but NASA postponed the mission after its GATV was destroyed during ascent to orbit. The agency decided that Gemini VI should instead pay a visit to the long-duration Gemini VII crew.
On 12 December, the Gemini VI Titan II booster ignited, then shut down before it could rise off its launch pad. Command Pilot Schirra opted not to trigger a perilous pad abort, saving the mission. On 15 December, Gemini VI at last lifted off and performed rendezvous and proximity operations with Gemini VII. As 1965 ended, NASA looked ahead to dockings and spacewalks in 1966.
Gemini VIII (Neil Armstrong and David Scott, 16-17 March 1966) became the first manned spacecraft to perform a docking - and the first Gemini mission with a successful GATV - but then suffered a thruster malfunction that sent the docked vehicles spinning out of control. The astronauts made an emergency landing, so Scott was unable to perform the planned first spacewalk since Gemini IV.
The Gemini VIII Reentry Module floats in the Pacific south of Japan after an emergency reentry which prevented Pilot David Scott (in left seat) from performing NASA's second spacewalk. Command Pilot Neil Armstrong sits in the right-hand seat. Image credit: NASADespite this, NASA proceeded with Gemini IX (Tom Stafford and Eugene Cernan, 1-11 June 1966) as if the Gemini VIII EVA had succeeded. Cernan, the agency announced, would move to the aft end of the Gemini IX Adapter Section, don the Astronaut Maneuvering Unit (AMU) - as the MMU had been renamed - and fly up to 45 meters from the spacecraft.
Cernan's spacewalk was a near-disaster. He quickly overheated, fogging his faceplate. He found that handholds, loop-shaped foot restraints, and velcro patches on Gemini IX's exterior gave him scant help in controlling his movements. He estimated after the flight that 50% of his energy had been devoted to fighting the internal pressure of his modified G4C suit so that he could hold position.
Nearly blinded by sweat, he tore his suit's outer thermal layers as he moved over Gemini's IX's hull. Through heroic efforts, and with his pulse racing at 195 beats per minute, he managed to reach and don the AMU before Stafford ordered him to abandon the EVA and return to Gemini IX’s cockpit.
NASA began hurriedly to revise its ambitious EVA plans. Gemini X (John Young and Michael Collins, 18-21 July 1966) started with a low-key EVA during which Collins performed astronomical ultraviolet photography while standing in the cockpit. During his second EVA, which began just 90 minutes after the first, he used an HHMU to move to the derelict Gemini VIII GATV.
Michael Collins in the Gemini X cockpit after his difficult spacewalk. Image credit: NASAHis clumsy movements caused the GATV to gyrate, making it difficult for Young to keep Gemini X close by. Young called off the EVA, which was to have lasted 90 minutes, just 39 minutes after Collins left the cockpit.
Gemini XI (Charles Conrad and Richard Gordon, 12-15 September 1966) was, if anything, even worse. Gordon quickly overheated as he fought without adequate handholds to attach a tether to the Gemini XI GATV. Conrad called off the scheduled 107-minute spacewalk after 38 minutes. In his post-flight debrief, Gordon reported that "a little simple task that I had done many times in training to the tune of about 30 seconds lasted about 30 minutes."
No Gemini performed a rendezvous with Pegasus 3. The meteoroid and thermal control test surface panels that the GEPG had hoped a spacewalker would recover during Gemini XI were destroyed when the satellite reentered Earth's atmosphere on 4 August 1969.
NASA kept the AMU on the manifest of Gemini XII (James Lovell and Edwin Aldrin, 11-15 November 1966), going so far as to install it on the spacecraft on 17 September 1966. On 23 September, however, as the significance of Gordon's EVA troubles hit home, NASA Headquarters ordered the hot-gas rocket pack removed.
In the pool: Buzz Aldrin trains for his Gemini XII spacewalks. Image credit: NASADesperate for a successful EVA, the agency revised Aldrin's training regimen and EVA plan. He spent extra time rehearsing his spacewalk while submerged in a swimming pool wearing weights that made him neutrally buoyant. His three EVAs had a relaxed pace and were spread out over three days. He had at his disposal a variety of new handholds, footholds, and other restraint devices. NASA also limited his EVAs to relatively simple tasks, such as testing space tools while firmly restrained.
The Soviet Union and Alexei Leonov maintained the fiction that his historic spacewalk had been "easy" until the late 1980s. After the fall of the Soviet Union in 1991, it was revealed that Leonov's Berkut suit had ballooned in the vacuum of space. He became unable to reach a camera switch on his thigh, so could not photograph Voskhod 2 as planned.
After about 10 minutes outside, Leonov began his return to Voskhod 2. He entered Volga head first (not feet first, as planned), so had to flip over in the airlock to shut its hatch behind him.
After becoming trapped sideways in the fabric airlock, he flirted with dysbarism ("the bends") by lowering his suit's internal pressure so that he could free himself, complete his flip, and seal the hatch. His exertions overwhelmed Berkut's air-flow cooling system, causing his core body temperature to rise 1.8° C in 20 minutes.
Leonov's EVA would be the last Soviet spacewalk until the Soyuz 4-Soyuz 5 docking mission of 14-18 January 1969. By the time Yevgeni Khrunov and Alexei Yeliseyev performed history's first two-person EVA on 16 January 1969, Soviet space suit designers and EVA planners had had time to benefit from NASA's Gemini EVA experience. Khrunov and Yeliseyev wore Yastreb space suits with cable-and-pulley systems and metal parts to prevent ballooning and improve mobility. Their 37-minute external transfer from Soyuz 5 to Soyuz 4 took place without significant incident.
Sources Memorandum with attachment, GS/Chairman, Gemini Extravehicular Planning Group, to Manager, Gemini Program, Report of Gemini Extravehicular Planning Study, 19 July 1965
"The First Egress of Man into Space," A. A. Leonov; paper presented at the 16th International Astronautics Congress in Athens, Greece, 13-18 September 1965
Walking to Olympus: An EVA Chronology, Monographs in Aerospace History Series #7, David S. F. Portree and Robert C. Trevino, NASA History Office, October 1997 -
http://history.nasa.gov/monograph7.pdf (accessed 3 June 2015)
Source:
The Spacewalks That Never Were: Gemini Extravehicular Planning Group (1965)