SM-65C Atlas
 Atlas C awaiting launch (USAF) | |
| Function | Prototype ICBM |
|---|---|
| Manufacturer | Convair |
| Country of origin | United States |
| Launch history | |
| Status | Retired |
| Launch sites | LC-12, CCAFS |
| Total launches | 6 |
| Successes | 3 |
| Failures | 3 |
| First flight | 24 December 1958 |
| Last flight | 24 August 1959 |
The SM-65C Atlas, or Atlas C was a prototype of the Atlas missile. First flown on 24 December 1958, the Atlas C was the final development version of the Atlas rocket, prior to the operational Atlas D. It was originally planned to be used as the first stage of the Atlas-Able rocket, but following an explosion during a static test on 24 September 1959, this was abandoned in favor of the Atlas D.
The Alas C test program began with the successful flight of 3C on December 24, 1958. On January 27, Missile 4C's guidance system quit working about a minute into flight, but the flight control system managed to compensate. The missile impacted in the South Atlantic some 40 miles (64 km) off target and the reentry vehicle also failed to separate.
Missile 5C (February 20) was a complete failure when the fuel disconnect valve did not close properly at booster separation. Fuel tank pressure was lost, leading to reversal of the intermediate bulkhead and missile self-destruction at T+172 seconds.
Missile 7C (March 19) suffered a guidance system failure at T+85 seconds, followed by premature booster cutoff at T+129 seconds. The Atlas's programmer sent a command to jettison the booster section at T+151 seconds, the point where normal BECO was supposed to occur. The sustainer engine thus burned until T+282 seconds, well past its normal cutoff point. Vernier cutoff took place at T+304 seconds. The Atlas traveled along an unstable trajectory for the remainder of powered flight, which made it impossible to determine where impact would occur. As such, the planned recovery of the RVX-2 reentry vehicle, which also failed to separate from the missile, was abandoned.
The final two C-series flights (8C on July 21 and 11C on August 24) were successful. Missile 8C was the third attempt to fly an RVX-2 reentry vehicle (the second attempt on a D-series Atlas had failed three months earlier) and the first successful one. Sixty-three minutes after launch, it was successfully recovered. Missile 11C carried a movie camera in the nose cone which filmed missile separation and a large portion of the Earth's surface on a 250-mile (402 km) lob, taking it to an apogee of 700 miles (1126 km). Recovery of the film capsule was successful.
One of the more significant upgrades to the Atlas C was the addition of motion detectors in the gyroscope package to ensure proper operation. This was implemented after the first B-series Atlas had failed in flight due to launch crews neglecting to power on the gyroscopes and would soon become a standard part of all ballistic missile guidance systems.
Missile 9C was designated for the Atlas-Able launch, which would take place in October 1959 from LC-12 at Cape Canaveral. The vehicle used the elongated propellant tanks first seen on Missiles 10B and 13B, but unfortunately this design change did not work as well here.
On September 24, the Atlas was prepared for a planned 12-minute PFRT (Pre-Flight Readiness Test). The upper stages were unfueled and the satellite was not on the launch vehicle. All went normally for two minutes when a fire erupted in the thrust section of the Atlas. Fed by leaking liquid oxygen, it proved impossible to put out with pad extinguishers and soon a huge inferno was raging on LC-12. Thirty-seven seconds after the fire began, the Atlas toppled over in a massive fireball, the biggest explosion seen at Cape Canaveral up to that point. The pad was severely damaged, with both umbilical towers totally destroyed, the concrete launch stand caved in, and the service tower knocked over. It would take months of repairs to get it back online. The final explosion was believed to be the result of fire-induced damage to the pneumatic system resulting in loss of tank pressure and structural failure of the Atlas. At around 35 seconds, the intermediate bulkhead collapsed, causing the LOX to fall into the RP-1 tank and mix. The propellants turned into a gel that detonated with the force of 20,000 pounds (9070 kg) of TNT and resulted in an extremely powerful explosion that caused extensive pad damage.
Investigators concluded that the disaster was due to the above-mentioned configuration change on the Atlas C, in addition to several weight-saving modifications unique to Missile 9C. When the Atlas was assembled at Convair, workmen attached a helium vent line to a port near the bottom of the RP-1 tank, below the anti-slosh baffles. Helium pressure gas from the vernier propellant tanks leaked into the sustainer RP-1 turbopump, leading to cavitation and rupture of the propellant lines. This then caused the fire that led to vehicle destruction. It was not clear whether the fire had been started by rupture of a LOX duct due to sudden pressure change from the helium venting or rubbing of the turbopump blades against the metal casing due to overspeed caused by the pump running without propellant in it. The accident was ultimately ruled to be the result of poor engineering judgement in attaching the vernier helium vent line to the bottom of the RP-1 tank.
After this debacle, it was decided instead to use the operational Atlas D for space launches instead of the developmental Atlas C.
Six flights were made. These were all sub-orbital test flights of the Atlas as an Intercontinental Ballistic Missile, with three tests succeeding, and three failing.
All Atlas C launches were conducted from Cape Canaveral Air Force Station, at Launch Complex 12.
Launch history
| Date | Time (GMT) | Serial | Apogee | Outcome |
|---|---|---|---|---|
| 1958-12-24 | 04:45 | 3C | 900 kilometres (560 mi) | Success |
| 1959-01-27 | 23:34 | 4C | 900 kilometres (560 mi) | Partial failure. Guidance system failed, however the flight control system managed to keep the missile on a stable path and impact was close to the target point. |
| 1959-02-20 | 05:38 | 5C | 100 kilometres (62 mi) | Failure. Valve malfunction during staging led to loss of tank pressure and reversal of the intermediate bulkhead. The missile destroyed itself at T+174 seconds. |
| 1959-03-19 | 00:59 | 7C | 200 kilometres (120 mi) | Partial failure. Premature booster engine shutdown due to an electrical malfunction at T+131 seconds led to an unstable flight trajectory. |
| 1959-07-21 | 05:22 | 8C | 900 kilometres (560 mi) | Success |
| 1959-08-24 | 15:53 | 11C | 900 kilometres (560 mi) | Success |
See also
References
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