|3 June 1965: Astronaut Ed White floats outside Gemini IV.|
The 5682-kilogram spacecraft carried a 1.2-meter-diameter inflatable airlock called Volga mounted over the inward-opening crew hatch of its 2.3-meter-diameter spherical reentry module. The airlock was necessary because Voskhod 2's electronics were air-cooled, so would overheat if its cramped cabin were depressurized. Following inflation - a process that lasted seven minutes - Volga extended 2.5 meters out from Voskhod 2's silvery hull.
At 0828 UTC, as the spacecraft neared the end of its first orbit, Leonov entered Volga and Belyayev sealed the Voskhod 2 hatch behind him. Belyayev then depressurized Volga, and Leonov opened its 65-centimeter-wide inward-opening outer hatch. At 0834 UTC, over northern Africa, the 30-year-old cosmonaut pulled himself through the hatch, kicked off the hatch rim, and floated away until he reached the end of his 5.35-meter-long safety tether and rebounded.
Leonov wore a white backpack containing enough oxygen for 45 minutes outside Voskhod 2. The oxygen entered his white Berkut space suit - a modified Vostok SK-1 intravehicular suit - then vented into space, carrying away exhaled carbon dioxide, heat, and moisture.
|The first spacewalker: cosmonaut Alexei Leonov. Image credit: TASS|
After the cosmonauts resealed the hatch, Belyayev fired explosive bolts that separated Volga from Voskhod 2. The spacecraft landed in the Soviet Union on 19 March after 17 Earth orbits. The Soviets declared that world's first spacewalk had been "easy."
NASA took notice. The U.S. civilian space agency had planned its first extravehicular activity (EVA) for Gemini IV, the second of 10 planned piloted Gemini missions. The Gemini IV EVA astronaut would not leave his spacecraft; instead, he would open his hatch (each Gemini astronaut had one) and stand up in the cockpit. This would test the G4C EVA suit and the life-support umbilical linking it to the Gemini spacecraft's life support system.
|Cutaway of Gemini spacecraft. Image credit: NASA|
Gemini IV's two-stage Titan II launch vehicle boosted it into a 283-by-161-kilometer, 94-minute orbit on 3 June 1965. Gemini IV separated from the Titan II second stage, then command pilot James McDivitt sought to rendezvous with it. The flight plan called for him to pilot Gemini IV to within seven meters of the stage during the mission's first orbit. Near the end of the second orbit, about three hours after launch, White would leave the cockpit and, using a Hand-Held Maneuvering Unit (HHMU), attempt to reach the spent stage.
Unfortunately, rendezvous proved to be more difficult than anticipated. The spent stage vented propellants, causing it to tumble. This subjected it to increased atmospheric drag, causing it to move away from Gemini IV. McDivitt set out in pursuit, but found his efforts thwarted by poor visibility, inability to accurately judge distance (Gemini IV included no rendezvous radar), and an incomplete grasp of orbital mechanics. With Gemini IV's propellant supply dwindling, McDivitt called off the rendezvous.
White then evaluated his umbilical. He found it to be useful for controlling his distance from Gemini IV and for pulling himself back to the spacecraft, but he was unable to demonstrate the precision maneuvering Leonov had reported. At one point, in fact, he accidentally collided with and smeared McDivitt's cockpit window.
White's life-support umbilical was covered in a thin layer of gold to protect it from the fierce sunlight of low-Earth orbit. If the umbilical had for any reason ceased to supply him with oxygen, his chest-mounted Ventilation Control Module (VCM) could have supplied him with enough to return safely to his seat.
As with Leonov's Berkut, oxygen passing through White's 10.7-kilogram G4C suit flushed exhaled carbon dioxide, heat, and moisture into space. America's first spacewalker reported later that he was more comfortable during his EVA than at any other time during the Gemini IV flight.
With Gemini IV moving rapidly toward night, White reluctantly returned to the cockpit. There he found that internal pressure had caused his suit to balloon slightly. During the five-minute struggle to squeeze back into his narrow seat and close his balky hatch, heat from White's exertions overcame the G4C’s cooling capacity. His visor fogged slightly and sweat blinded him until he could remove his helmet in the repressurized cockpit and wipe his eyes.
NASA judged White's 20-minute EVA to have been a resounding success. EVA, it seemed, presented few challenges. NASA management was, on the other hand, alarmed by McDivitt's inability to rendezvous with the Titan II second stage. Rendezvous was a critical part of NASA's Lunar Orbit Rendezvous plan for landing a man on the moon by 1970.
By the end of June, NASA top brass were considering cancelling the progressively more challenging EVAs scheduled for Gemini missions V, VI, and VII so that engineers, flight controllers, and astronauts could concentrate on rendezvous.
In July 1965, NASA made decisions critical to Gemini EVA planning. On 2 July, the Gemini Program Office (GPO) at the Manned Spacecraft Center (MSC) in Houston, Texas, formed the Gemini Extravehicular Planning Group (GEPG) to revise EVA objectives for Gemini missions VIII, IX, X, XI, and XII. On 12 July, NASA Headquarters directed the GPO to postpone the next U.S. spacewalk until Gemini VIII. The GEPG submitted its recommendations to Gemini Program Manager Charles Mathews on 19 July.
The GEPG based its recommendations on several assumptions. First, of course, was that the EVA objectives planned for Gemini VIII would be attainable without the gradual development of skills that would have occurred during the Gemini V, VI, and VII EVAs.
|Gemini Agena Target Vehicle (docking adapter at right). Image credit: NASA|
The GEPG also recommended that EVA equipment too large for cockpit storage be stowed on the aft-facing concave surface of the Adapter Section, the aft-most and widest part of the Gemini spacecraft, as well as on the GATV. On Gemini VIII, oversize equipment would include an HHMU with 10 times as much compressed oxygen as White's HHMU. The Gemini VIII EVA astronaut would evaluate the Adapter Section stowage concept, then test the HHMU.
The GEPG noted that oxygen flow through White's space suit had kept him cool and dry "except when [he] was working at a high exertion level." On Gemini VIII and subsequent missions, an Extravehicular Life Support System (ELSS) would replace the VCM. The ELSS could be used with a backpack-mounted oxygen supply that would permit hour-long EVAs without an umbilical. The GEPG recommended that the Gemini VIII EVA astronaut test the ELSS chest-pack to ensure that it could cool even a hard-working spacewalker adequately.
Before returning to the cockpit, he would also "inspect the Agena for engineering analysis," test a space hand tool, and evaluate a lightweight safety tether and a backup "suit exhaust" EVA propulsion system. By clambering over the two spacecraft, he would evaluate transfer between two vehicles, a skill of potential use in the Apollo Program if astronauts found themselves compelled in the event of docking problems to move by EVA between the Apollo Command and Service Module (CSM) and Lunar Module (LM).
The many EVA tasks planned for Gemini VIII through XII would require EVAs of greater duration than White's, so the Gemini VIII spacewalker would also evaluate EVA operations during orbital night, which would last for about half of each orbit.
|U.S. Air Force Modular Maneuvering Unit. Image credit: NASA|
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: NASA|
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.
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: NASA|
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: NASA|
Until the late 1980s, the Soviet Union and Alexei Leonov maintained the fiction that his historic spacewalk had been "easy." 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 was 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. Unable to adequately control his movements, he entered Volga head first (not feet first, as planned), so had to flip 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. When Yevgeni Khrunov and Alexei Yeliseyev performed history's first two-person EVA on 16 January 1969, Soviet space suit designers and EVA planners drew upon 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.
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)