The Disappointing Flight of NASA’s Mercury-Atlas 1

With test flights of America’s latest generation of crewed spacecraft being followed by space enthusiasts around the globe, it is widely expected that these flights will be nearly perfect with no major problems encountered. What is frequently forgotten all these decades later is how often the first test flights of crewed spacecraft failed at the dawn of the Space Age as engineers worked to perfect a wide range of new technologies all at once. One of the more heartbreaking of these early failures was NASA’s first attempt to launch their brand new Mercury spacecraft into space on July 29, 1960 for the uncrewed Mercury-Atlas 1 mission.

Artist concept of the Mercury capsule with its launch escape system. (NASA)

The Plan

The goal of NASA’s Project Mercury was to send a single astronaut into orbit using a modified version of the Atlas D ICBM built by the Convair division of General Dynamics – the largest rocket the US had available at the time. The highly innovative Atlas used an integral balloon tank design where the millimeter-thick, stainless steel structure acted as both the outer shell and propellant tanks with internal pressure providing the rigidity needed to keep it from collapsing. To further improve its performance, the Atlas used an equally innovative propulsion system developed by North American Aviation’s Rocketdyne Division (today part of Aerojet Rocketdyne) which was designated MA-2. It consisted of a pair of Rocketdyne LR-89 boosters generating 687 kilonewtons of thrust each and a central LR-105 sustainer engine rated at 253 kilonewtons. All three of these engines would ignite on the launch pad to get the Atlas off the ground. After the ascending rocket had shed enough mass and gained sufficient altitude, it would jettison the pair of booster engines and their supporting structure. Greatly lightened, the Atlas would continue to accelerate powered by the single sustainer engine and the pair of verniers feeding off the remaining RP-1 grade kerosene and liquid oxygen (LOX) propellants in the tanks.

Diagram comparing the Mercury-Atlas and Atlas ICBM. Click on image to enlarge. (NASA)

The Space Task Group (STG) based at NASA’s Langley Research which was responsible for the Project Mercury naturally wished to include several uncrewed test flights using the Atlas as part of the manned program’s larger test program. This was especially important given the high failure rate during the first test flights of this cutting edge ICBM. The first Atlas-based test flight, designated “Big Joe”, used Atlas 10D to launch a boilerplate model of the Mercury capsule on a suborbital trajectory on September 9, 1959. Among the objectives was to test Mercury’s ablative heat shield under actual reentry conditions as well as test the recovery systems. Although the Atlas failed to jettison its booster engines during ascent, resulting in the capsule coming down 800 kilometers short of its planned recovery zone 3,200 kilometers downrange, the flight proved that the ablative heatshield worked as well as verified the aerodynamic stability of the Mercury capsule design (see “Giving Mercury Its Wings: The First Test Flights of NASA’s Mercury Program”).

The launch of the Mercury Big Joe mission from LC-14 during the early-morning hours of September 9, 1959. (USAF)

For the second Atlas flight of the Mercury program, the intent was to fly an actual production model Mercury spacecraft on a brief suborbital flight. The objectives of this mission included verifying the structural integrity of the Mercury spacecraft during flight, determine the spacecraft’s heating rates and flight dynamics during reentry, determine the adequacy of Mercury’s recovery systems as well as train Project Mercury personnel with launch and recovery operations. The Atlas 50D rocket was assigned to support this mission to be designated Mercury-Atlas 1 (MA-1). This rocket was essentially identical to Atlas 10D flown in the Big Joe mission save for a thickening of the stainless steel used in the fuel tank at the base of the rocket by 0.03 to 0.08 millimeters and the addition of the Abort Sensing and Implementation System (ASIS) to be used in the event of a failure during ascent.

Atlas 50D being prepared for the Mercury-Atlas 1 mission. (Convair via SDASM)

Mercury spacecraft number 4 built by McDonnell Aircraft in St. Louis was assigned to the MA-1 test flight. Unlike later flights, this spacecraft would not be flown with a launch escape system mounted on top since the system was still under development and not required to support this mission’s objectives. Instead, this capsule was fitted with a tower stub needed to hold a thermal fairing in place on the nose of the spacecraft which protected an antenna and the parachute cannister. Without the launch escape system, the ASIS was set up to inhibit spacecraft separation during an abort situation until 170 seconds after launch when the tower was no longer needed to support launch abort options.

Mercury Spacecraft No. 4 being mounted atop Atlas 50D. Note the short launch escape tower stub holding a thermal fairing at the top of the spacecraft. (Convair via SDASM)

Spacecraft No. 4 also did not include an astronaut couch, display panels or an environment control system. Also excluded was the attitude control system to further simplify the spacecraft and its operation. This allowed the spacecraft to simulate a complete control system failure where the attitude of the spacecraft during reentry would be maintained by the inherent aerodynamic stability of capsule design. The capsule would include a 90-kilogram instrumentation package built by NASA’s Lewis Research Center (today known as the Glenn Research Center) similar to the one carried on the Big Joe flight. It housed a pair of cameras, tape recorders and a 16-channel telemetry system to monitor the spacecraft’s condition. The instrumentation included a set of 50 temperature sensors to monitor heating loads during ascent and reentry. While the spacecraft carried a retrorocket package, the retrorockets themselves were inert. Only the posigrade motors needed to separate the spacecraft from the Atlas were live. The total spacecraft mass at launch was 1,162 kilograms, including the retropack and the tower stub.

Map showing the planned trajectory of the Mercury-Atlas 1 mission with the location of tracking and recovery assets as they were to be deployed. Click on image to enlarge. (NASA)

The mission called for liftoff from Launch Complex 14 (LC-14) at Cape Canaveral down the Atlantic Missile Range. After booster engine separation, MA-1 would ascend to a maximum altitude of 182 kilometers before arcing back towards the Earth under the power of the sustainer engine. The altitude at sustainer cutoff would be 166.7 kilometers with the spacecraft travelling at 5,777 meters per second at an angle of 3.61° below the local horizontal. This trajectory would simulate a return from orbit. After enduring reentry with peak braking loads of 16.3 g, the drogue chute would be deployed at an altitude of 13 kilometers followed by the main parachute at three kilometers. The reserve parachute was not to be used on this flight and was carried simply as ballast. The Mercury capsule would then splashdown 2,400 kilometers downrange after a flight of about 16 minutes when it would be recovered.

The All Too Brief Flight

When STG first drew up its first test schedule in January 1959, the Mercury-Atlas 1 flight was penciled in for launch in November 1959. Delays in spacecraft construction and the availability of Atlas rockets eventually pushed this overly ambitious launch date out by eight month to July of 1960. Pressure on Project Mercury only increased when the Soviet Union launched a prototype of its crewed spacecraft on an unmanned orbital test flight on May 15, 1960 (see “Korabl-Sputnik & The Origin of the Soviet Vostok Program”). The first piece of mission hardware to arrive at Cape Canaveral was Atlas 50D on May 17, 1960. Six days later, Spacecraft No. 4 arrived ready for flight save for flight instrumentation, parachutes and pyrotechnic devices. After its post shipment inspection and initial systems checks, Atlas 50D was erected on the pad at LC-14 on June 30. On July 6, Spacecraft No. 4 was mated to the Atlas for the first time.

Mercury Spacecraft No. 4 shown mounted on top of Atlas 50D in preparation for the Mercury-Atlas 1 mission. (NASA)

After a successful fuel tanking test, the Mercury capsule was removed on July 7 and returned to Hanger S to correct issues uncovered during the mating test as well as rework selected instrumentation and telemetry packages. In the mean time, Atlas 50D completed a LOX tanking test on July 8. Spacecraft No. 4 was mated to the Atlas again on July 11 to prepare for the Flight Acceptance Composite Test (FACT) of the full stack in two days. While the Convair team had met all of its objectives for Atlas 50D, problems were encountered with the capsule stretching out the FACT to July 18. Afterwards, the capsule was removed once more to make final corrections while Atlas 50D successfully performed a live firing of its MA-2 propulsion system on July 21. Spacecraft No. 4 was mated to Atlas 50D for the last time on July 26 to begin final preparations for a launch attempt in three days.

Mercury-Atlas 1 shown with the gantry in place as it is being prepared for launch. (NASA)

Mercury-Atlas 1 began its final 215-minute countdown at 3:55 AM EST on July 29, 1960 under overcast skies with intermittent rain. The countdown proceeded smoothly with only minor problems encountered until a hold was called at the T-35 minute mark to finish pyrotechnic hookup and address issues with cameras at the launch complex. The hold was extended to 30 minutes as the weather conditions and camera coverage were assessed. Another brief hold in the countdown was called at the T-7 minute mark to allow the LOX tank top off to be completed. At T-19 seconds, another one-minute hold was called to correct a minor blockhouse issue. The countdown was then recycled to the T-25 second mark.

The launch of Mercury-Atlas 1 from LC-14 on July 29, 1960. (NASA)

Mercury-Atlas 1 lifted off from LC-14 at 8:13:03 AM EST and quickly accelerated out of sight as it penetrated the overcast with a ceiling varying from 450 to 2,700 meters. All seemed to be going well with MA-1 which was travelling at 466 meters per second (Mach 1.56) at an altitude of 10.3 kilometers 58.2 seconds after launch as maximum dynamic pressure (max q) was approached. At 58.5 seconds after launch, a large disturbance was recorded subjecting the Mercury capsule to a forward force of 25 g. While the spacecraft seemed undamaged by the event, all telemetry from the Atlas was lost less than a second later as ground radar detected multiple objects.

Although the overcast prevented a view from the ground, it was apparent that MA-1 had broken up near max q. Spacecraft No. 4 continued transmitting for another 143 seconds after the Atlas failure. While the Atlas ASIS had shutdown the MA-2 engines upon sensing the abort situation, the Mercury capsule remained attached to the booster’s remains since its abort sequence was inhibited until 170 seconds after launch. MA-1 impacted the Atlantic about 10 kilometers downrange 198 seconds after launch.

The remains of Mercury Spacecraft No. 4 after the recovered pieces were reassembled. (NASA)

With this heartbreaking failure, the long task of determining its cause began. The wreckage of Atlas 50D and Spacecraft No. 4 were located in about 18 meters of water near its predicted impact point and efforts were made to recover as much debris as possible. Initial suspicions for the failure centered on the thermal fairing and tower stub breaking loose at max q with the debris puncturing the LOX tank. There were also concerns that the absence of the launch escape tower had altered the aerodynamics of the ascending stack resulting in excessive drag, acceleration and bending loads on Atlas causing its stainless steel skin to buckle just behind the capsule. NASA called for the interface with the Atlas to be redesigned and the forward section of the Atlas stiffened while the Mercury-Atlas trajectory was altered to reduce bending loads in future flights. Investigating and correcting these issue further delayed Mercury-Atlas flights as NASA struggled to launch the first person into space.

Follow Drew Ex Machina on Facebook.

General References

Loyd S. Swenson Jr., James M. Grimwood and Charles C. Alexander, This New Ocean: A History of Project Mercury, NASA SP-4201, 1966

“Post Launch Report for Mercury-Atlas No. 1 (MA-1)”, Space Task Group, NASA, August 2, 1960

“Flight Test Report Mercury/Atlas MA-1 (Atlas 50D) July 29, 1960”, WS-107A-1 Flight Test Working Group, August 22, 1960