Mercury-Redstone Launch Vehicle
Encyclopedia
The Mercury-Redstone Launch Vehicle, designed for NASA
's Project Mercury
, was the first American
manned space booster. It was used for six sub-orbital Mercury flights from 1960–61; culminating with the launch of the first, and 11 weeks later, the second American (and the second and third humans) in space.
A member of the Redstone rocket family
, it was derived from the U.S. Army's Redstone ballistic missile
and the first stage
of the related Jupiter-C
launch vehicle; but to make it man-rated, its structure and systems were modified to improve safety and reliability.
The four subsequent Mercury manned flights used the more powerful Atlas booster
to enter low Earth orbit
.
NASA chose the U.S. Army's Redstone liquid-fueled ballistic missile for its sub-orbital flights because it was the most reliable of any U.S. ballistic missile at the time, with many successful test flights.
The standard military Redstone lacked sufficient thrust to lift a Mercury capsule into the ballistic sub-orbital trajectory needed for the project; however, the first stage of the Jupiter-C
, which was a modified Redstone with lengthened fuel tanks, could carry enough propellant to reach the desired trajectory. Therefore this Jupiter-C first stage was used as the starting point for the Mercury-Redstone design. The Jupiter-C's engine, however, was being phased out by the Army, so to avoid potential complications such as parts shortages or design revisions, the Mercury-Redstone designers chose the Rocketdyne
A-7 engine used on the latest military Redstones.
The standard Redstone was fueled with a 75 percent ethyl alcohol solution, but the Jupiter-C first stage had used hydyne
fuel, a blend of 60 percent unsymmetrical dimethylhydrazine (UDMH) and 40 percent diethylenetriamine (DETA). This was a more powerful fuel than ethyl alcohol, but it was also more toxic, which could be dangerous for an astronaut in a launch pad emergency. Furthermore, hydyne had never been used with the new A-7 engine. The Mercury-Redstone designers rejected hydyne and returned to the standard ethyl alcohol fuel.
The most important change in making the Mercury-Redstone a suitable vehicle for an astronaut was the addition of an automatic in-flight abort sensing system. In an emergency where the rocket was about to suffer a catastrophic failure, an abort would activate the launch escape system
attached to the Mercury capsule, which would rapidly eject it from the booster. Either the astronaut or the ground controllers could initiate an abort manually, but some potential failures during flight could lead to disaster before an abort could be manually triggered.
The Mercury-Redstone's automatic in-flight abort sensing system solved this problem by monitoring the rocket's performance during flight. If it detected an anomaly which might threaten the astronaut, such as loss of flight control, engine thrust, or electrical power, it would automatically abort, shutting down the engine and activating the capsule's escape system. (To keep the rocket from falling on people or facilities in the launch area, automatic engine shutdown was disabled during the first 30 seconds of flight, while the rocket was still over land.) An automatic abort could be triggered by any of the following conditions:
Like many rockets, the Mercury-Redstone also had a destruct system so ground controllers could destroy a malfunctioning rocket before it could threaten people on the ground. But for the Mercury-Redstone, the astronaut would need time for the escape system to carry him a safe distance from the rocket before it was destroyed, so the destruct system would automatically delay itself until three seconds after an abort was given.
The most visible difference between the Jupiter-C first stage and the Mercury-Redstone was in the section just below the Mercury capsule and above the propellant tanks. This section was known as the aft section, a term which was inherited from the military Redstone. (The actual rear end of the rocket was called the tail section.) The aft section held most of the Mercury-Redstone's electronics and instrumentation, including the guidance system, as well as the adapter for the Mercury capsule. In the military Redstone and the Jupiter-C first stage, when the rocket had burned out, its lower portion, containing the rocket engine and propellant tanks, would separate from the aft section and be discarded, and the aft section, with its guidance system, would direct the top half of the rocket during its unpowered ballistic flight. However, in the Mercury-Redstone, the aft section was permanently attached to the lower portion of the rocket. When the rocket had shut down, the Mercury capsule would separate from the aft section and would rely on its own guidance.
Other changes were made to improve the Mercury-Redstone's reliability. The standard Redstone's ST-80 inertial guidance system was replaced in the Mercury-Redstone with the simpler LEV-3 autopilot. The LEV-3, whose design dated back to the German V-2 missile, was not as sophisticated or as precise as the ST-80, but it was accurate enough for the Mercury mission and its simplicity made it more reliable. A special instrument compartment was built in the "aft section" to hold the most important instrumentation and electronics, including the guidance system, the abort and destruct systems, the telemetry
instrumentation, and the electrical power supplies. To reduce the chance of failure in this equipment, this compartment was cooled before launch and kept pressurized during flight.
The space between the pressurized instrument compartment and the capsule was originally intended to hold a parachute recovery system for the rocket. When this system was abandoned, the compartment was used for ballast to improve stability in flight. Unlike the standard Redstone, the Mercury-Redstone's length and heavy payload caused it to become aerodynamically unstable later in the flight as it reached supersonic speeds, but the extra ballast delayed the onset of this effect past the most critical period of maximum aerodynamic forces, known as "max Q
".
The recovery system, at the top of the rocket, would have used two stages of parachutes. In the first stage, a single parachute, 17 feet (5.2 m) in diameter, would stabilize the rocket's fall and slow its descent. This parachute would then draw out a set of three main parachutes, each 67 feet (20.4 m) across. The rocket would come down in the Atlantic Ocean, to be recovered by ship.
To determine the feasibility of this system, several tests were performed on full-sized Redstones, including water impact and flotation tests, and an exercise at sea in which a floating Redstone was picked up by a Navy recovery ship. All these tests showed recovery of the rocket to be workable. Further development was halted, however, due to lack of funding, so the parachute system was not tested.
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
's Project Mercury
Project Mercury
In January 1960 NASA awarded Western Electric Company a contract for the Mercury tracking network. The value of the contract was over $33 million. Also in January, McDonnell delivered the first production-type Mercury spacecraft, less than a year after award of the formal contract. On February 12,...
, was the first American
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
manned space booster. It was used for six sub-orbital Mercury flights from 1960–61; culminating with the launch of the first, and 11 weeks later, the second American (and the second and third humans) in space.
A member of the Redstone rocket family
Redstone (rocket family)
The Redstone family of rockets consisted of a number of American ballistic missiles, sounding rockets and expendable launch vehicles operational during the 1950s and 60s. The first member of the family was the PGM-11 Redstone missile, from which all other members were derived. The first large U.S...
, it was derived from the U.S. Army's Redstone ballistic missile
Ballistic missile
A ballistic missile is a missile that follows a sub-orbital ballistic flightpath with the objective of delivering one or more warheads to a predetermined target. The missile is only guided during the relatively brief initial powered phase of flight and its course is subsequently governed by the...
and the first stage
Multistage rocket
A multistage rocket is a rocket that usestwo or more stages, each of which contains its own engines and propellant. A tandem or serial stage is mounted on top of another stage; a parallel stage is attached alongside another stage. The result is effectively two or more rockets stacked on top of or...
of the related Jupiter-C
Jupiter-C
The Jupiter-C was an American sounding rocket used for three sub-orbital spaceflights in 1956 and 1957 to test re-entry nosecones that were later to be deployed on the more advanced PGM-19 Jupiter mobile missile....
launch vehicle; but to make it man-rated, its structure and systems were modified to improve safety and reliability.
The four subsequent Mercury manned flights used the more powerful Atlas booster
Atlas LV-3B
The Atlas LV-3B, Atlas D Mercury Launch Vehicle or Mercury-Atlas Launch Vehicle, was a man-rated expendable launch system used as part of the United States Project Mercury to send astronauts into low Earth orbit. It was derived from the SM-65D Atlas missile, and was a member of the Atlas family of...
to enter low Earth orbit
Low Earth orbit
A low Earth orbit is generally defined as an orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km...
.
Modifications from the Redstone missile
The standard military Redstone lacked sufficient thrust to lift a Mercury capsule into the ballistic sub-orbital trajectory needed for the project; however, the first stage of the Jupiter-C
Jupiter-C
The Jupiter-C was an American sounding rocket used for three sub-orbital spaceflights in 1956 and 1957 to test re-entry nosecones that were later to be deployed on the more advanced PGM-19 Jupiter mobile missile....
, which was a modified Redstone with lengthened fuel tanks, could carry enough propellant to reach the desired trajectory. Therefore this Jupiter-C first stage was used as the starting point for the Mercury-Redstone design. The Jupiter-C's engine, however, was being phased out by the Army, so to avoid potential complications such as parts shortages or design revisions, the Mercury-Redstone designers chose the Rocketdyne
Rocketdyne
Rocketdyne was a Rocket engine design and production company headquartered in Canoga Park, California, United States. The company was related to North American Aviation for most of its history. NAA merged with Rockwell International, which was then bought by Boeing in December, 1996...
A-7 engine used on the latest military Redstones.
The standard Redstone was fueled with a 75 percent ethyl alcohol solution, but the Jupiter-C first stage had used hydyne
Hydyne
Hydyne, also unofficially known as Bagel fuel, is a mixture of 60% unsymmetrical dimethylhydrazine and 40% diethylenetriamine , developed in 1957 at Rocketdyne for use in liquid-fuel rockets....
fuel, a blend of 60 percent unsymmetrical dimethylhydrazine (UDMH) and 40 percent diethylenetriamine (DETA). This was a more powerful fuel than ethyl alcohol, but it was also more toxic, which could be dangerous for an astronaut in a launch pad emergency. Furthermore, hydyne had never been used with the new A-7 engine. The Mercury-Redstone designers rejected hydyne and returned to the standard ethyl alcohol fuel.
The most important change in making the Mercury-Redstone a suitable vehicle for an astronaut was the addition of an automatic in-flight abort sensing system. In an emergency where the rocket was about to suffer a catastrophic failure, an abort would activate the launch escape system
Launch escape system
A Launch Escape System is a top-mounted rocket connected to the crew module of a crewed spacecraft and used to quickly separate the crew module from the rest of the rocket in case of emergency. Since the escape rockets are above the crew module, an LES typically uses separate nozzles which are...
attached to the Mercury capsule, which would rapidly eject it from the booster. Either the astronaut or the ground controllers could initiate an abort manually, but some potential failures during flight could lead to disaster before an abort could be manually triggered.
The Mercury-Redstone's automatic in-flight abort sensing system solved this problem by monitoring the rocket's performance during flight. If it detected an anomaly which might threaten the astronaut, such as loss of flight control, engine thrust, or electrical power, it would automatically abort, shutting down the engine and activating the capsule's escape system. (To keep the rocket from falling on people or facilities in the launch area, automatic engine shutdown was disabled during the first 30 seconds of flight, while the rocket was still over land.) An automatic abort could be triggered by any of the following conditions:
- Pitch, yaw, or roll angle deviating too far from the programmed flight profile,
- Pitch or yaw angle changing too rapidly,
- Pressure in the engine's combustion chamber falling below a critical level,
- Loss of electrical power for the flight control system, or
- Loss of general electrical power (including power for the abort sensing system itself), which could indicate a catastrophic failure.
Like many rockets, the Mercury-Redstone also had a destruct system so ground controllers could destroy a malfunctioning rocket before it could threaten people on the ground. But for the Mercury-Redstone, the astronaut would need time for the escape system to carry him a safe distance from the rocket before it was destroyed, so the destruct system would automatically delay itself until three seconds after an abort was given.
The most visible difference between the Jupiter-C first stage and the Mercury-Redstone was in the section just below the Mercury capsule and above the propellant tanks. This section was known as the aft section, a term which was inherited from the military Redstone. (The actual rear end of the rocket was called the tail section.) The aft section held most of the Mercury-Redstone's electronics and instrumentation, including the guidance system, as well as the adapter for the Mercury capsule. In the military Redstone and the Jupiter-C first stage, when the rocket had burned out, its lower portion, containing the rocket engine and propellant tanks, would separate from the aft section and be discarded, and the aft section, with its guidance system, would direct the top half of the rocket during its unpowered ballistic flight. However, in the Mercury-Redstone, the aft section was permanently attached to the lower portion of the rocket. When the rocket had shut down, the Mercury capsule would separate from the aft section and would rely on its own guidance.
Other changes were made to improve the Mercury-Redstone's reliability. The standard Redstone's ST-80 inertial guidance system was replaced in the Mercury-Redstone with the simpler LEV-3 autopilot. The LEV-3, whose design dated back to the German V-2 missile, was not as sophisticated or as precise as the ST-80, but it was accurate enough for the Mercury mission and its simplicity made it more reliable. A special instrument compartment was built in the "aft section" to hold the most important instrumentation and electronics, including the guidance system, the abort and destruct systems, the telemetry
Telemetry
Telemetry is a technology that allows measurements to be made at a distance, usually via radio wave transmission and reception of the information. The word is derived from Greek roots: tele = remote, and metron = measure...
instrumentation, and the electrical power supplies. To reduce the chance of failure in this equipment, this compartment was cooled before launch and kept pressurized during flight.
The space between the pressurized instrument compartment and the capsule was originally intended to hold a parachute recovery system for the rocket. When this system was abandoned, the compartment was used for ballast to improve stability in flight. Unlike the standard Redstone, the Mercury-Redstone's length and heavy payload caused it to become aerodynamically unstable later in the flight as it reached supersonic speeds, but the extra ballast delayed the onset of this effect past the most critical period of maximum aerodynamic forces, known as "max Q
Max Q
In aerospace engineering, the maximum dynamic pressure, often referred to as maximum Q or max Q, is the point at which aerodynamic stress on a vehicle in atmospheric flight is maximized...
".
Proposed parachute recovery system
The Mercury-Redstone designers originally planned for the rocket to be recovered by parachute after its separation from the Mercury capsule. This was the first significant effort to develop a recoverable launch vehicle and the first to reach the testing phase.The recovery system, at the top of the rocket, would have used two stages of parachutes. In the first stage, a single parachute, 17 feet (5.2 m) in diameter, would stabilize the rocket's fall and slow its descent. This parachute would then draw out a set of three main parachutes, each 67 feet (20.4 m) across. The rocket would come down in the Atlantic Ocean, to be recovered by ship.
To determine the feasibility of this system, several tests were performed on full-sized Redstones, including water impact and flotation tests, and an exercise at sea in which a floating Redstone was picked up by a Navy recovery ship. All these tests showed recovery of the rocket to be workable. Further development was halted, however, due to lack of funding, so the parachute system was not tested.
Flights
Mercury-Redstone flights were designated with the prefix "MR-". Confusingly, the Mercury-Redstone boosters used for these flights were designated in the same way, usually with different numbers. (In photographs, this designation can sometimes be seen on the rocket's tail end.) Two rockets, MR-4 and MR-6, were never flown.| Flight designation | Rocket designation | Launch date | Comments |
|---|---|---|---|
| MR-1 Mercury-Redstone 1 Mercury-Redstone 1 was the first Mercury-Redstone mission in the Mercury program and the first attempt to launch a Mercury spacecraft with the Mercury-Redstone launch vehicle. Intended to be an unmanned sub-orbital flight, it was launched on November 21, 1960 from Cape Canaveral, Florida... |
MR-1 | November 21, 1960 | Empty capsule; launch abort; rocket shut down at liftoff due to electrical fault |
| MR-1A Mercury-Redstone 1A Mercury-Redstone 1A was launched on December 19, 1960 from LC-5 at Cape Canaveral, Florida. The mission objectives of this unmanned suborbital flight were to qualify the spacecraft for space flight and qualify the system for an upcoming primate suborbital flight. The spacecraft tested its... |
MR-3 | December 19, 1960 | Empty capsule |
| MR-2 Mercury-Redstone 2 Mercury-Redstone 2 was an American space mission, launched at 16:55 UTC on January 31, 1961 from LC-5 at Cape Canaveral, Florida. Mercury spacecraft No... |
MR-2 | January 31, 1961 | Carried chimpanzee Ham Ham the Chimp Ham , also known as Ham the Chimp and Ham the Astrochimp, was the first chimpanzee launched into outer space in the American space program... |
| MR-BD Mercury-Redstone BD Mercury-Redstone BD was an unmanned booster development flight in the U.S. Mercury program. It was launched on March 24, 1961 from Launch Complex 5 at Cape Canaveral, Florida... |
MR-5 | March 24, 1961 | Empty nonfunctional "boilerplate" capsule |
| MR-3 Mercury-Redstone 3 Mercury-Redstone 3 was the first manned space mission of the United States. Astronaut Alan Shepard piloted a 15-minute Project Mercury suborbital flight in the Freedom 7 spacecraft on May 5, 1961 to become the first American in space, three weeks after the Soviet cosmonaut Yuri Gagarin had carried... |
MR-7 | May 5, 1961 | Carried astronaut Alan Shepard Alan Shepard Alan Bartlett Shepard, Jr. was an American naval aviator, test pilot, flag officer, and NASA astronaut who in 1961 became the second person, and the first American, in space. This Mercury flight was designed to enter space, but not to achieve orbit... |
| MR-4 Mercury-Redstone 4 Mercury-Redstone 4 was the second United States manned space mission, launched on July 21, 1961. The Mercury program suborbital flight used a Redstone rocket. The spacecraft was named Liberty Bell 7 piloted by astronaut Virgil I. "Gus" Grissom. It reached an altitude of more than 118.26 mi ... |
MR-8 | July 21, 1961 | Carried astronaut Gus Grissom Gus Grissom Virgil Ivan Grissom , , better known as Gus Grissom, was one of the original NASA Project Mercury astronauts and a United States Air Force pilot... |