1965-027A
Project SNAPSHOT was a joint effort between the US Air Force and the Atomic Energy Commission (AEC) to test a fully functioning nuclear reactor in Earth orbit. The vehicle was attached to Agena 7001.
SNAP 10A was 440 kg including a 102 kg shield and a 14 kg heat shield.
A secondary payload sometimes described as an ionosphere beacon experiment is actually the SECOR geodetic satellite.
A fairing covered the reactor at launch; two side panel heat shields were jettisoned on orbit.
The SNAP is 436 kg, but there is also a cylindrical instrument section carrying secondary payloads and equipment; the Agena/instrument section was 1964 kg for a total dry mass of 2400 kg. Actual on orbit mass would be less than this by the mass of the heat shield and possibly the nose fairing.
SNAP is a cone 3.5m long 1.3m dia, the instrument section is around 1.3m long 1.5m dia and the Agena about 6.3m long 1.5m dia.
The reactor (40 kW nominal reactor power for 500W of provided electrical power) had U235 fuel moderated by ZrH and with beryllium reflectors; NaK-78 coolant was circulated through the system. It converted heat to energy via a SiGe thermoelectric converter. The reactor is shielded using lithium hydride. In addition to an aerodynamic nose fairing, the thermoelectric converter is surrounded by an ejectable heat shield "to prevent NaK plugging prior to startup", i.e. to prevent freezing of the NaK. The reactor had 37 fuel elements in a triangular array.
An ion engine test was carried; electromagnetic interference caused false horizon sensor data and `severe' attitude perturbations.
The reactor is described in SNAP Reactor Overview (S. Voss, 1984), AFWL-TN-84-14.
1965-27E, Catalog SSN 01399, has been associated with three different objects.
(1) An object in a 111.51 min, 1270 x 1321 km x 90.2 deg orbit was observed from Jun 1965 to Apr 1971. It appears to be a duplicate of the SNAPSHOT payload.
(2) An object in a 106.89 min, 1024 x 1141 km x 89.9 deg orbit was observed from Dec 1968 to Sep 1970. Based on its orbit and orbital plane it was probably a duplicate of 1965-48A, Transit NNS O-4; element sets on 1969 Feb 11 and 1970 Sep 13 are essentially identical.
(3) An object in a 101.07 min, 750 x 867 km x 90.5 deg orbit was first observed in Nov 1972. In Jul 1988 it had decayed to 671 x 739 km; all SSN 01399 elements since 1972 have been for this object. It is probably Transit debris - and might be associated with the 1972 TRIAD launch which was in a similar orbit and was close in orbital plane in Nov 1972. However, the inclination is different by 0.4 deg.
In around 1979, small debris objects began to be cataloged from SNAPSHOT. It is believed they emanate from the Agena and are similar to other small debris from SEASAT's Agena. The objects were released over many years rather than in one event.
| SNAPSHOT | |||
| Date | Time | Event | Orbit |
|---|---|---|---|
| 1965 Apr 3 | 2124 | Launch by Atlas Agena D | V |
| T+2:14 BECO | |||
| 2126 | Booster sep | ||
| 2128 | T+4:29 Atlas SECO | ||
| 2128 | Atlas sep | ||
| 2130 | T+6:00 Agena MES-1 | ||
| Nose cone ejected | |||
| 2133:40 | T+9:40 Agena MECO-1 | 161 x 1290? x 90.0 | |
| 2222? | Ionosphere beacon jettison at 1300 km | ||
| 2222:17? | T+58:17 Agena MES-2 10s | 111.6 1282 x 1313 x 90.0 | |
| 2222:27? | T+58:27 MECO-2 | ||
| 2230? | EGRS sep (rev 0) | ||
| 1965 Apr 4 | 0105 | Reactor startup | |
| Ion engine telemetry failed | |||
| 0300? | Reactor critical | ||
| 1965 Apr 4 | 0500? | Full power 600W | |
| 0738? | `sensible heat' generated, H+0 | ||
| 1965 Apr 4 | 0744? | H+6min Heat shield halves ejected (reactor at 275F, L+10:20?) | |
| 0942? | Rev 7, Temp switch closure | ||
| 1965 Apr 5 | 0530? | Rev 18, ion engine operation | |
| EMI problems cause vehicle slew | |||
| Ion engine shut down | |||
| 1965 Apr 10 | 0524 | Passive control phase begins | |
| 1965 May 16 | 1635 | Voltage regulator failed, auto shutdown, rev 555. | |
| F+1h reflectors ejected but connected by cables | |||
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