Mercury-Redstone 1A

The story of Mercury-Redstone 1A does not begin on 19 December 1960 but in the objectives NASA had written for Mercury-Redstone 1. MR-1A carried no test of its own: it repeated, item by item, what the previous flight should have demonstrated. That copied character explains its designation — a letter appended to the earlier mission rather than a new number — and it also makes the flight an unusually clean record of how Project Mercury recovered from a setback: without redesigning the mission, without widening its objectives, and without using the delay to slip extra tests aboard.

The 21 November 1960 attempt had failed as briefly as it did spectacularly. The launch ended in a premature cutoff of the launch vehicle engines when the vehicle had risen about an inch off the pad; the cutoff activated the emergency escape system, and the Redstone settled back onto the pad with only slight damage. The cause was traced to a premature loss of electrical ground power to the booster. Because the spacecraft had received a cutoff signal, the escape tower and the recovery sequence fired, and the capsule came through undamaged and available for reuse. Seen from the hardware side the outcome was almost benign: neither spacecraft nor booster was destroyed, and the programme kept the material for another try.

Before that attempt there had been one that never reached the final count. On 7 November 1960 the mission was scrubbed because of a helium leak in the relief valve of the spacecraft's reaction control system. Counting all three, MR-1A was the third assault on a single set of objectives, and the programme chronology says so explicitly.

MR-1 was not the only reverse of those weeks. On 8 November 1960 Little Joe 5 was launched from Wallops Island, the first of the series to carry a McDonnell production spacecraft, to check the capsule in an abort simulating the most severe launch conditions. The flight was normal until 15.4 seconds after lift-off, when the escape rocket motor ignited prematurely; the spacecraft did not detach from the launch vehicle until impact and was destroyed. The failure was attributed to several possible causes, all involving the clamp-ring limit switches or their rigging, and a repeat of the mission had to be scheduled. Thirteen days later came the MR-1 failure.

In parallel, NASA personnel met at Langley Field on 16 November 1960 to review the test programmes, establish the causes of the Mercury-Atlas 1 failure and determine the readiness status of Mercury-Atlas 2. In the month before MR-1A, in other words, the Redstone, Little Joe and Atlas branches of the programme each had an open failure on the table. That is the real scale of what rode on a flight that, on paper, merely repeated what had already been planned.

The vehicle that flew as MR-1A was capsule number 2, the same one from the 21 November attempt. It had been delivered to the launch site on 23 July 1960 and its preparation record eventually totalled twenty-one weeks, with the explicit remark that the spacecraft was reworked after the MR-1 launch attempt in which the launch vehicle malfunctioned. That rework is the material difference between the two missions: the capsule had endured an escape-tower firing and a full recovery sequence on the ground, and had to be restored to flight condition. NASA's uncrewed-missions summary refers to it as spacecraft number 2A, a distinction that points to the post-incident reconfiguration.

The booster, by contrast, was a different article. The Redstone assigned to MR-1A was shipped to Cape Canaveral on 3 December 1960. Barely four weeks separated the failure from the new flight, and only half of that time passed with the booster already at the Cape — a cadence that shows how firmly the programme regarded the problem as bounded rather than structural.

The programme's test-objectives appendix lists five items for MR-1A. The first was to qualify the spacecraft-booster combination for the Mercury-Redstone mission, broken down into three concrete quantities the flight had to produce: a Mach number of approximately 6 during powered flight, a period of weightlessness of about five minutes, and a deceleration of approximately 11 g on reentry. The remaining four were system qualifications: the posigrade rockets, the recovery system, the launch, tracking and recovery phases of operation, and the Automatic Stabilization and Control System including the Reaction Control System.

The chronology adds the second-order purpose that governed the schedule: qualify the spacecraft for space flight and qualify the flight system for the primate flight scheduled shortly thereafter. MR-1A was therefore not a milestone in its own right but the door that had to be opened before Mercury-Redstone 2 could fly with a living passenger.

MR-1A lifted off from Launch Complex 5 at Cape Canaveral on 19 December 1960. Attention centred on how the spacecraft-launch vehicle combination behaved through the successive flight sequences: powered flight, acceleration and deceleration, performance of the posigrade rockets, performance of the recovery system, performance of the launch, tracking and recovery phases of the operation, and other flight events including retrorocket operation in a space environment and the operation of the instrumentation.

All of those sequences were met. Tower separation, spacecraft separation, spacecraft turnaround, retrofire, retropackage jettison and landing-system operation occurred or were controlled as planned. The trajectory produced a maximum altitude of 130.68 statute miles — 690,000 feet in the programme's flight data summary, about 210.3 km — a maximum range of 234.8 statute miles and a maximum space-fixed velocity of 4,909.1 miles per hour, equivalent to 7,200 feet per second space-fixed and 6,350 feet per second earth-fixed. Total flight duration was 15 minutes and 45 seconds, with some five and a half minutes of weightlessness, a maximum dynamic pressure of 560 pounds per square foot and a peak acceleration of 12.4 g.

Recovery closed the mission without incident: fifteen minutes after landing in the Atlantic Ocean, the recovery helicopter picked up the spacecraft.

The flight was rated completely successful, yet the chronology does not present it as flawless. It records one explicit exception: the launch vehicle cutoff velocity was slightly higher than normal. That is the only departure from plan the institutional source notes, and it appears as a caveat — "except that…" — inside an otherwise clean balance sheet. The excess cutoff velocity is consistent with the flight's final figures, which came out above those of a nominal Mercury-Redstone profile, and it foreshadows one of the matters the programme would have to settle before putting a man atop the same rocket.

Work did not end when the capsule was hoisted aboard. The MR-1A postlaunch system evaluation tests were completed at Cape Canaveral on 16 January 1961, and the data showed that the instrumentation system, the communication system and other components had operated satisfactorily during the mission. That verification, performed on recovered hardware rather than on telemetry alone, is what turned "the flight went well" into a formal qualification of the systems.

There is also an operational result the chronology credits jointly to MR-1 and MR-1A: during both launches the complete Mercury Control Center staff operated for the first time. In that particular respect the November failure and the December success served the same end — the first full shakedown of the flight-control organisation.

The handover to Mercury-Redstone 2 was immediate and is documented by date. On 2 December 1960, before the flight, the Space Task Group had forwarded to the Marshall Space Flight Center the weight and balance values for capsule 5, the one assigned to MR-2. On 20 December 1960, a single day after the MR-1A success, the Redstone launch vehicle for MR-2 — the chimpanzee Ham flight — was delivered to Cape Canaveral. And on 31 January 1961, six weeks after MR-1A, MR-2 flew with the primate aboard.

The MR-2 objectives show precisely what MR-1A had spared it. While MR-1A shouldered the qualification of the spacecraft-booster combination, the posigrade rockets, the recovery system, the phases of operation and the stabilisation and control system, MR-2 could devote itself to what could not be tested without a living passenger: obtaining physiological and performance data on a primate in ballistic space flight, qualifying the Environmental Control System and the aeromedical instrumentation, qualifying the landing bag system, partially qualifying the voice communication system and qualifying the mechanically actuated side hatch. Without 19 December that division of labour would have been impossible, and MR-2 would have had to absorb the basic qualification of the combination as well.

Success did not spare the Redstone one more test before crewed flight. On 24 March 1961, after analysing launch vehicle behaviour on MR-1A and MR-2, officials at the Marshall Space Flight Center and the Space Task Group concluded that a number of problems still needed correcting before crewed flight arrived: jet-vane vibration, instrumentation compartment vibration, failure of the thrust-controller system and several other areas requiring attention. Solutions were formulated, but a flight was judged necessary to verify them, and the Mercury-Redstone Booster Development test was scheduled and flown for that purpose.

That epilogue places MR-1A exactly where it belongs in the programme: it was the mission that proved the combination worked end to end and that allowed the move to a primate flight, not the one that declared the Redstone fit to carry an astronaut. Between 19 December 1960 and Alan Shepard's flight of 5 May 1961 there still lay MR-2, the March review and the booster development flight.