Apollo A-002: Testing the Limits of the Launch Escape System

One of the more dangerous parts of a space mission is launch which is why almost all crewed spacecraft have had launch abort options to cover all phases of ascent. In order to support abort options on the pad through the earliest parts of the flight, many crewed spacecraft have included a launch escape system (LES) consisting of an independent propulsion package to pull the crew capsule off and away from a malfunctioning launch vehicle and to safety. In the over than six decades of crewed spaceflight, an LES was used only once for the “Soyuz T-10A” pad abort in 1983 (see “Soyuz T-10A: The First Crewed On-Pad Abort”).

The American Apollo, like the earlier Mercury spacecraft, also employed an LES but, its design and operation had to be verified through a series of ground and uncrewed flight tests to ensure that it would work as intended. This was especially important in the early days of the Space Age before the availability of sophisticated computer simulation software. To this end, NASA planners included a series of test flights to validate the operation of the LES under specific stressful conditions Apollo would experience during its ascent into space.

Testing the Apollo LES

The Apollo Launch Escape System (LES) was built by the Lockheed Propulsion Company (whose corporate parent is now part of Lockheed Martin). It consisted of a rocket motor assembly attached to the top of the Apollo Command Module (CM) by means of a truss framework with a total height of 9.9 meters and a mass of 4,200 kilograms. The main propulsion system of the LES of consisted of a solid rocket motor fitted with four nozzles that produced a nominal thrust of 650 kilonewtons for four seconds to lift the CM and LES away from the launch vehicle in case of an abort situation on the pad or during the initial phases of ascent. It also included a deployable canard system and a pitch motor rated at 18 kilonewtons to help stabilize the CM/LES during an abort and steer it out of the path of the malfunctioning launch vehicle. A smaller solid rocket motor with a pair of nozzles producing about 140 kilonewtons of thrust was used to pull the LES off of the ascending Apollo spacecraft when it was no longer needed to support abort options about three minutes after launch.

Diagram illustrating the major components of the Apollo Launch Escape System (LES). Click on image to enlarge. (NASA)

In order to test Apollo hardware under the most stressing flight conditions that it would experience during an abort situation at high altitudes and velocities, NASA contracted the production of the Little Joe II rocket. The original Little Joe was developed to perform abort tests in support of the Mercury program starting in 1959 (see “Giving Mercury Its Wings: The First Test Flights of NASA’s Mercury Program“). The Little Joe was meant to be a simple, adaptable and inexpensive launch vehicle that would employ various combinations of readily available solid rocket motors firing together or in a preplanned sequence to lift test hardware to a desired speed and altitude to exercise the LES under a range of stressing abort situations. On May 11, 1962, the Convair Division of General Dynamics got the contract to develop and build the larger Little Joe II to support the Apollo program.

Diagram showing the typical configuration of the Apollo-Little Joe II. Click on image to enlarge. (NASA)

The Little Joe II was a fin-stabilized rocket with the same 3.96-meter diameter as the Apollo CM it was to lift. With the Apollo CM, a dummy service module (SM) and flightworthy LES in place, the Apollo-Little Joe II had a total height of 26.2 meters. The internal configuration of the Little Joe II allowed up to seven Aerojet General Algol 1D solid rocket motors to be carried with each producing 465 kilonewtons of thrust for 40 seconds.  Similar Algol motors were being used at this time as the first stage in NASA’s Scout all-solid launch vehicle. Up to six smaller Recruit solid motors could also be carried to provide a 1.5 second kick to aid in liftoff. By varying the number and firing sequence of all these motors, a large range of abort situations could be simulated to altitudes as great as 60.9 kilometers (although none of the Apollo abort tests would actually fly that high).

An exploded view of the Little Joe II and its major components. Click on image to enlarge. (NASA)

A typical test would have the Little Joe II lift the CM/LES combination to a desired altitude and velocity at which point the LES would ignite and pull the CM away from the rocket to perform the abort test and subsequent recovery sequence.  The White Sands Missile Range (WSMR) in New Mexico was chosen as the launch site for the abort tests because of the increasingly busy schedule at Cape Kennedy hampered abort test scheduling.  In addition, land recoveries were easier to perform and less expensive than water recoveries.

Diagram showing the events of a typical Apollo-Little Joe II abort test flight. Click on image to enlarge. (NASA)

Like other early test flights of the Apollo, the first abort flights with the Little Joe II did not use actual Apollo flight hardware. Instead engineers employed boilerplate models which mimic the mass, shape and dynamic properties of actual flight hardware but otherwise only carried systems and instruments needed for the tests being conducted. Their low cost and adaptability made boilerplate models ideal for the first Apollo engineering test flights.

The Apollo A-002 Flight

By the end of 1964, NASA had already successfully flown a CM boilerplate for the first Apollo Little Joe II flight (see “The First Apollo Little Joe II Launch”) as well as two boilerplate spacecraft on orbital flights with the Saturn I which tested LES separation under actual flight conditions, among other engineering tasks (see “The First Apollo Orbital Test Flight”, and “The Second Apollo Orbital Test Flight”). The objectives of the second Apollo Little Joe II flight, designated A-002, were to demonstrate the LES performance at maximum dynamic pressure or “max q”. Also to be tested for the first time on this flight was the Boost Protective Cover (BPC). The BPC was a structure attached to the LES which covered the CM and was built of fiberglass and cork. It helped to protect the outer hull and windows of the Apollo CM during its initial ascent and jettisoning of the LES.

Diagram showing the configuration of Little Joe II vehicle number 12-51-1 for the Apollo A-002 abort test. Click on image to enlarge. (General Dynamics)

In order to meet the objectives for this flight, Little Joe II vehicle number 12-51-1 was fitted with a pair of Algol motors and four smaller, quick-burning Recruit rocket motors. With all six motors ignited at launch from WSMR Launch Complex 36, this Little Joe II generated 1,600 kilonewtons of thrust at lift off. Little Joe II 12-51-1 was also the first to be fitted with an active attitude control system (ACS) using a combination of hydraulic actuators to move control surfaces on the rocket’s fins and a reaction control system using hydrogen peroxide jets. This system was required to initiate a pitch up maneuver 35.5 seconds after launch to produce the required angle of attack limit for this test just prior to LES ignition. At this time, the Apollo-Little Joe II would be at an altitude of 9.5 kilometers traveling at Mach 1.5. The LES would be activated two seconds later at an altitude of 10.3 kilometers.

BP-23 being raised into position atop of the Little Joe II in preparation for the A-002 flight. (NASA)

The payload for this mission consisted of BP-23 and its LES which had a combined mass of 11,492 kilograms. In addition to carrying the flight systems needed to support the mission, BP-23 carried a radar beacon, instrumentation to make a total of 95 in-flight measurements and a telemetry transmitter to return the data live during the flight. With this payload mounted atop Little Joe II 12-51-1, the total launch mass of the stack was 42,788 kilograms including 3,905 kilograms of ballast.

The launch of Apollo-Little Joe II A-002 on December 8, 1964 carrying BP-23. (NASA)

After an uneventful 8-hour countdown, the A-002 mission lifted off from LC-36 on an azimuth of 0° and an elevation angle of 84.03° at 8:00 AM MST on December 8, 1964. During ascent, the Little Joe II initiated its “pitch up” maneuver 2.4 seconds earlier than intended due to a computer error subjecting the ascending vehicle to about 29% greater dynamic loads than planned. Still, the LES activated 35.7 seconds after launch and pulled BP-23 away from its launch vehicle. About 11 seconds later, the LES canards were deployed in order to turn the CM into the proper blunt side first attitude for LES jettison 121.3 seconds after launch. After reaching a peak altitude of 15.35 kilometers above sea level, the CM’s recovery system was activated 123.3 seconds after launch at an altitude of 7.16 kilometers. BP-23 safely landed in the New Mexico desert on its three parachutes 9.99 kilometers downrange after a flight lasting 7 minutes and 23 seconds. The only significant issue during the flight was that the new BPC was damaged during the test indicating that its design was structurally inadequate.

The recovery of BP-23 following the A-002 flight. (NASA)

As for the rest of the flight hardware, the Little Joe II 12-51-1 launch vehicle broke up shortly after the abort, as expected, due to excessive aerodynamic loads. Debris from the rocket were scattered over a large area about six kilometers downrange. The four control fins and the reaction control system were located, deactivated, and recovered for post flight analysis along with other key components. Not found were the command destruct module assembly and the BPC which had disintegrated after LES jettison. The spent LES was also recovered from the desert downrange of the launch site.

The remains of the LES from the A-002 flight burrowed into the desert floor following its jettisoning. (NASA)

Following the A-002 flight, BP-23 was found to still be in excellent condition. After recovery, the boilerplate CM was refurbished and redesignated BP-23A. It was subsequently reflown for the second (and last) pad abort test, PA-2, launched from White Sands on June 29, 1965. BP-23A survived this test and is currently on display in the Davidson Saturn V Center at the US Space and Rocket Center in Huntsville, Alabama.

Pad abort test PA-2 flown on June 29, 1965 using the refurbished BP-23A. (NASA)

Related Reading

“The First Apollo Little Joe II Launch”, Drew Ex Machina, May 13, 2014 [Post]

“Soyuz T-10A: The First Crewed On-Pad Abort”, Drew Ex Machina, September 26, 2019 [Post]

General References

David Baker, The Rocket: The History and Development of Rocket & Missile Technology, Crown, 1978

Neil A. Townsend, “Apollo Experience Report – Launch Escape Propulsion Subsystem”, NASA Technical Note D-7083, March 1973

“Little Joe II Test Launch Vehicle, NASA Project Apollo – Final Report Volume II Technical Summary”, General Dynamics Convair Division GDC-66-042, May 1966