Project Aphrodite

Project Aphrodite was the U.S. Air Force's fourth spaceflight program based on off-the-shelf components of Big Pilgrim, an enlarged version of the Pilgrim capsule used to transport personnel to the MOL. The primary purpose of the program was to test various interplanetary spaceflight procedures before a proposed crewed mission to the planet Mars in the 1980s. The USAF proposed the project to send two astronauts on a flyby mission to Venus in a Pilgrim-derived spacecraft in 1973-1974, using a gravity assist to shorten the return journey to Earth. 
In 1971, Russian engineer and science fiction writer Sergei Zhitomirsky proposed the concept of "floating islands on Venus" which served as an inspiration of the Venus Glider that was used on Aphrodite V-5. The first time a glider craft was used on another planetary body until Project HOPE in 2007. 
The German space effort had also proposed a crewed mission to the planet Venus during the early 1970s but this was abandoned as Dr. von Braun felt dedicating fully to the Mars project would prove more efficient than becoming distracted with Venus.
== Pilgrim Extension Program ==
In the mid-1960s, the USAF and NASA considered a "two-man flyby of Venus" as part of the Pilgrim Extension Program, using hardware derived from the Pilgrim program. Several mission profiles were considered for launch during the 1970s. 
=== Background ===
The proposed mission would have used a Saturn V to send three astronauts on a flight past Venus, which would have lasted approximately one year. The S-IVB stage would have been a "wet workshop" similar to the original design of Skylab. In this concept, the interior of the fuel tank would be filled with living quarters and various equipment that did not take up a significant amount of volume. The S-IVB would then be filled with propellants as normal and used to accelerate the craft on its way to Venus. Once the burn was complete, any remaining propellant would be vented to space, and then the larger fuel tank could be used as living space, while the smaller oxygen tank would be used for waste storage.
Only so much equipment could be carried in the hydrogen tank without taking up too much room, while other pieces could not be immersed in liquid hydrogen and survive. This equipment would instead be placed in the interstage area between the S-IVB and the Apollo Command/Service Module (CSM), known as the Spacecraft-LM Adapter (SLA), which normally held the Apollo Lunar Module on lunar missions. To maximize the amount of space available in this area, the Service Propulsion System engine of the CSM would be replaced by two LM Descent Propulsion System engines. These had much smaller engine bells, and would lie within the Service Module instead of extending out the end into the SLA area. This also provided redundancy in the case of a single-engine failure. These engines would have been responsible for both course correction during the flight and the braking burn for Earth re-entry.
Unlike the Apollo lunar missions, the CSM would perform its transposition and docking maneuver with the S-IVB stage before the burn to leave Earth orbit, rather than after. This meant the astronauts would have flown "eyeballs-out", the thrust of the engine pushing them out of their seats rather than into them. This was required because there was only a short window for an abort burn by the CSM to return to Earth after a failure in the S-IVB, so all spacecraft systems needed to be operational and checked out before leaving the parking orbit around Earth to fly to Venus.
Precursors to the Venus flyby would include an initial orbital test flight with an S-IVB "wet workshop" and basic docking adapter, and a year-long test flight taking the S-IVB to a near-geostationary orbit around the Earth.
=== Scientific objectives ===
The mission would have measured:
* Density, temperature and pressure of Venus' atmosphere as functions of altitude, latitude and time.
* Definition of the planetary surface and its properties.
* Chemical composition of the low atmosphere and the planetary surface.
* Ionospheric data such as radio reflectivity and electron density and properties of cloud layers.
* Optical astronomy – UV and IR measurements above the Earth's atmosphere to aid in the determination of the spatial distribution of hydrogen.
* Solar astronomy – UV, X-ray and possible infrared measurements of the solar spectrum and space monitoring of solar events.
* Radio and radar astronomy - radio observations to map the brightness of the radio sky and to investigate solar, stellar and planetary radio emissions; radar measurements of the surface of Venus and Mercury
* X-ray astronomy – measurements to identify new X-ray sources in the galactic system and to obtain additional information on sources previously identified.
* Data on the Earth-Venus interplanetary environment, including particulate radiation, magnetic fields and meteoroids.
* Data on the planet Mercury, which would have been in mutual planetary alignment with Venus approximately two weeks after the Venus flyby.
== Missions ==
* Aphrodite V-1. Launch would have taken place on October 31, 1973, with a Venus flyby on March 3, 1974 and return to Earth on December 1, 1974.
* Aphrodite V-2. Launched January 1975, returned 13 months later in February 1976.
* Aphrodite V-3. Launched July 1976, returned 13 months later in August 1977.
* Aphrodite V-4. Launched January 1978, returned 13 months later in February 1979.
* Aphrodite V-5. Launched July 1979, returned 13 months later in August 1980. First and only use of a powered glider through the atmosphere of the planet Venus, in November 1979.
* Aphrodite V-6. Cancelled in 1973.
* Aphrodite V-7. Cancelled in 1973.
* Aphrodite V-8. Cancelled in 1973.
Category:Space projects
Category:United States