Gemini spaceship
| Gemini spaceship | ||
|---|---|---|
|
||
| description | ||
| Use: | Earth orbit | |
| Crew: | 2: Commander and Pilot | |
| Dimensions | ||
| Height (landing capsule with coupling adapter): | 3.4 m | |
| Height (device unit): | 2.3 m | |
| Height (total): | 5.8 m | |
| Diameter: | 3.0 m | |
| Dimensions: | 3800 kg | |
| Gemini spaceship | ||
The Gemini spacecraft was used by the US space agency NASA for the Gemini program . Between 1964 and 1966 there were two unmanned and ten manned flights, which made it possible to gain significant experience for the Apollo program and the moon landing .
conditions
The Gemini program was supposed to fill the gap between the Mercury program and the already planned Apollo program.
The spaceship should enable the development and testing of various methods and procedures that were absolutely necessary for a manned moon landing:
- Engines that not only allow changes in position, but also orbit changes
- Facilities for rendezvous and docking maneuvers
- Facilities for spacewalks
- Execution of long-term flights of up to two weeks
- Control during re-entry
In addition, the Gemini spaceship should be transported into space by rockets available at the time and use existing rocket upper stages as a coupling target.
Compared to Mercury, this required a different design. The most important differences were the modular structure, in which many elements were accessible from outside the cabin, and the use of ejection seats in the event of an aborted take-off.
Naming
The Latin name Gemini means twin and mainly refers to the twins Castor and Pollux from Roman mythology, as well as the constellation of twins named after them . This name was chosen for the spaceship because it could hold two astronauts. The program was officially named on January 3, 1962, after a request for proposals in December 1961. The name Gemini was suggested by two people.
development
Like the Mercury spaceship before it, the Gemini spaceship was developed and manufactured by the McDonnell company in St. Louis . The design came from the Canadian Jim Chamberlin , who had previously been responsible for the aerodynamics of the CF-105 Arrow interceptor . The development took place in close cooperation with the NASA astronauts, who were represented by Virgil Grissom .
Early designs of the Gemini spaceship were based on an expansion of the Mercury spaceship, called the Mercury Mark II. However, the necessary modifications would have meant that the existing launch vehicles could not have launched the spaceship. For this reason, the spaceship was designed from scratch.
Another design from the early days pursued the idea that the spaceship should not go down in the water, but on solid land, which would have made salvage by the US Navy unnecessary. For this purpose, paragliders and a landing gear should be installed. This draft did not prevail. A prototype can be seen today at the Royal Museum in Edinburgh, Scotland .
Structure and equipment
construction
The spaceship consisted of three parts: coupling adapter, landing capsule and device unit. The structure of the spaceship consisted mainly of titanium and magnesium as a compromise between resilience and weight.
One of the biggest differences from the Mercury spaceship was a separate drive and equipment unit that contained various systems. Before the start, these devices were accessible from the outside. This part of the spaceship was blown off before reentry and burned up in the earth's atmosphere.
The ablative heat shield was on the wide end of the re-entry module.
Landing capsule
cabin
The cabin contained two contour couches as well as instruments, life support systems and electrical supplies. There wasn't much room in the cabin; the astronauts almost hit the hatch with their helmets. The crew could hardly stretch out. Getting in and out of an outboard mission was extremely arduous. Because of the narrow space, the astronauts jokingly named the spaceship "Gusmobile" after Gus Grissom , the smallest of their group.
The two hatches could be opened and closed while in space so that activities outside the spaceship were possible. The hatches were mechanically locked and opened outwards. A triple-glazed viewing window in the hatch made observations possible. In an emergency, the hatches were opened automatically when the ejection seat was triggered.
Ejection seat
In the event of a false start or a problem during the waterfall, the astronauts could have used the ejection seat , which was manufactured by Weber Aircraft .
Each of the two astronauts could activate the ejection seat in an emergency, but both seats were always deployed. The mechanism would have blown open the hatches first, then catapulted the seats out of the spaceship. A rocket built into the seat would have brought the astronauts out of the danger zone, whereby accelerations of up to 24 g would have to be endured until the parachute with a diameter of 8.5 m would have opened.
When Gemini 6 was aborted , Walter Schirra was on the verge of triggering the ejection seats because the engines had switched off again shortly after the ignition and there was a risk that the rocket, if it had already taken off, would fall back onto the launch pad. He decided not to do so because he (correctly) suspected that the rocket - contrary to the announcement - had not yet taken off.
Parachutes
Before the splashdown, the Gemini spaceship was slowed down by several parachutes that were used one after the other.
The first parachute (High Altitude Drogue Parachute) had a diameter of 2.5 m and was located at the tip of the coupling adapter. It was triggered at an altitude of 15,000 m.
At an altitude of 3200 m, the next parachute, the so-called pilot parachute with a diameter of 5.6 m, was deployed by the astronauts. Shortly after it had unfolded, the coupling adapter was blasted off at a height of 3000 m, as a result of which the main umbrella was pulled out of the position and unfolded. The main screen was 25.7 meters in diameter and consisted of nylon strips in white and orange.
In the event of the high altitude drogue parachute malfunctioning, the astronauts could have manually detached the coupling adapter and triggered the main parachute. In the event of a total failure, it would still have been possible to catapult yourself out of the spaceship using the ejection seat. Had this happened at an altitude of over 2300 m, a balloon screen would have been used, which would have stabilized and delayed the astronaut until the parachute opened at an altitude of 1700 m. The balloon umbrella had a diameter of about 120 cm and a length of 140 cm. It could be used up to an altitude of 22,500 m.
Technical facilities
power supply
In the first examples, energy was supplied exclusively by batteries, later by polymer electrolyte fuel cells . The spaceship's electrical system ran on 25 volts DC. Devices that required AC voltage used their own inverters .
Life support systems
The life support systems supplied the astronauts with oxygen and water and ensured a comfortable temperature in the cabin and spacesuit. Carbon dioxide, moisture and urine were also disposed of.
Since the devices in the spaceship developed much more heat than those in the Mercury spaceship, and that over a much longer period of time, temperature control was particularly important. The temperature in the cabin was typically around 18 ° C and rose to around 49 ° C during re-entry. 93 ° C was assumed as the predictable maximum.
The cabin atmosphere during the flight consisted of pure oxygen at a pressure of approx. 0.34 bar. The oxygen supply required for this took place beginning two hours before the start up to the separation from the device unit shortly before re-entry by the primary system. The oxygen was kept in a spherical tank in the equipment unit. The backup system consisted of two tanks in the re-entry module and ensured normal consumption for about three hours. It was activated as planned after the primary system had been disconnected or when the pressure in it fell below 5.2 bar. A third oxygen system would have been activated if the astronauts had to catapult themselves out of the cabin with the ejection seat. The carbon dioxide exhaled by the astronauts was removed from the cabin atmosphere using lithium hydroxide filters.
Water was available in several tanks in the device unit and return unit. About 18 l could be used for cooling and also as drinking water via a drinking tube. From Gemini 5 , the energy supply was carried out by fuel cells which not only provided electrical energy but also water.
computer
.JPG)
With the Gemini Digital Computer (also Gemini Guidance Computer ), the Gemini spaceship was the first to have a computer on board that could calculate flight maneuvers. It consisted of five circuit boards that were equipped with discrete components and weighed 26.6 kg. The computer had a memory of 160 kbit (4096 words of 39 bits each). Additions, subtractions, and transfers could be done in 140 microseconds, multiplications in 420 microseconds, and divisions in 840 microseconds.
communication
The Gemini spaceship was equipped with shortwave and VHF radios, both for duplex voice traffic and for data transmission in both directions. The data was transmitted both frequency-modulated in real time and delayed (temporarily stored on a tape drive) in PCM modulation.
A radiotelephone connection existed with the crew of the launch center before take-off and was possible with the rescue teams until after the ditch.
The radio traffic was only interrupted twice as planned. The first interruption occurred during re-entry , lasted about 6 to a maximum of 8 minutes, and was caused by plasma . The second interruption of about 30 seconds took place when the main parachute was opened, after the antenna in the coupling adapter had just been disconnected and the next antenna had not yet been set up.
The spaceship had two radar transmitters. A C-band transponder and an S-band transponder worked as secondary radar , whereby the C-band signal could be emitted via various antenna diagrams. A radio transmitter was used for rough recording.
Engines
The Gemini spaceship had three different engine systems.
Attitude control thrusters
The Orbit Attitude And Maneuver System (OAMS) was used for attitude control and for maneuvering the spaceship. It was active for most of the flight, from the separation of the final rocket stage at launch to the separation of the piece of equipment just before re-entry.
The OAMS consisted of 16 permanently mounted engines with constant thrust:
- Eight engines each had 110 N thrust. They were ignited in pairs to turn the spaceship around one of the three spatial axes.
- Six engines each had 440 N thrust. They were used for movements along the three spatial axes
- Two engines with a thrust of 380 N each were mounted at the tip of the spaceship and provided thrust to the rear.
Monomethylhydrazine was used as the fuel, and nitrous tetroxide as the oxidizer . The tanks were pressurized with helium to deliver fuel. The amount of fuel varied from mission to mission.
An error occurred in the OAMS during the flight of Gemini 8 when a nozzle jammed and the spaceship tumbled uncontrollably. The astronauts Neil Armstrong and David Scott succeeded in switching off the OAMS and using the RCS to bring the spaceship back under control. According to the mission rules, however, the mission had to be canceled.
Braking missiles
The brake rocket system (Retrograde Rocket System, RRS) consisted of four solid rockets, each with 11 kN thrust, which were mounted on the device unit. To exit orbit, the rockets were fired one after the other at 5.5 second intervals. Then the missiles were detached.
Reentry Control Systems (RCS)
The Reentry Control System (RCS) was installed in the reentry module in front of the cabin. It consisted of two identical systems that were independent of each other for reasons of redundancy. Even if one of the systems failed, the other could have ensured a safe landing at the intended landing point.
Each of the two propulsion systems consisted of eight permanently installed liquid propulsion units of 110 N each. As with the OAMS, monomethylhydrazine and nitrous oxide from cylindrical titanium tanks were used, but nitrogen was used to regulate the pressure.
Further use
In addition to the development of the Gemini spaceship actually used, NASA commissioned further studies to investigate expanded possible uses. Technically it would even have been possible to make a flight to the moon with the Gemini spaceship, but with a different launcher. The plans to orbit the moon were not pursued because NASA had the Apollo project with a manned landing as a stated goal by the end of the decade.
From 1963, the US Air Force had plans to use the Gemini spacecraft for the military space station Manned Orbiting Laboratory (MOL). An unmanned test flight took place on November 3, 1966, with the Gemini 2 spacecraft being reused. The program was discontinued in 1969.
Use and whereabouts
A total of 12 airworthy copies were made. The first two, Gemini 1 and Gemini 2 , were used for an orbital and a suborbital unmanned test flight. The manned maiden flight took place on March 23, 1965 with Gemini 3 , the last mission was carried out in November 1966 with Gemini 12 .
Gemini 1 burned up in the earth's atmosphere. The return pods of the other spaceships were handed over to museums in the United States after landing:
The flight time was not continuously increased because the flights had different destinations. Gemini 3 and 4 were purely test flights, Gemini 5 and 7 long-term flights. The short mission Gemini 6 only had the rendezvous with Gemini 7 as its goal. The Gemini 8 to 12 missions had docking and space exits as their goal, and the Gemini 8 mission had to be canceled.
literature
- Barton C. Hacker and James M. Grimwood: On the Shoulders of Titans: A History of Project Gemini. NASA History Series, Washington DC 1977 ( online ).
- James M. Grimwood, Barton C. Hacker, Peter J. Anteroom: Project Gemini: Technology and Operations. A Chronology. NASA History Series, Washington DC 1969 ( online ).
Web links
- Gemini in the Encyclopedia Astronautica (English)
- NASA: Project Gemini Drawings and Technical Diagrams (English)
- Gemini Technical Description in the Encyclopedia Astronautica (English)
Individual evidence
- ↑ Helen T. Wells, Susan H. Whiteley, Carrie E. Karegeannes: Gemini. In: Origins of NASA Names. NASA History Office, 1976, p. 104 , accessed June 25, 2011 .
- ↑ Gemini in the Encyclopedia Astronautica, accessed on June 24, 2011 (English). Plans for various extensions to the Gemini spaceship.
- ↑ Lunar Gemini in the Encyclopedia Astronautica, accessed June 10, 2011 (English).
- ↑ museum move reunites historic Gemini 6 spacecraft with its pilot . Collectspace, July 31, 2018.