V. Engineering Mechanics Performance

A. Temperature Control Failure Analysis (L. B. Katter)

1. There are six transducers directly indicating structure temperature. Three of these (two on sun sensors and one on the +Y jet vane actuator) read within the predicted band. The remaining three, namely: the helium tank, the nitrogen tank and the temperature control transducers read 4, 16 and 8 degrees above the top of their predicted bands, respectively.

In addition, there are six transducers which indirectly indicate the structure temperature. These are the gyro, the boost regulator, the attitude control DC converter, the transponder, the battery and power switch and logic temperature transducers. Five of these six indicate the structure to be within predicted band, one (the transponder) indicates the structure was 100 above band.

In summary, we have four transducers indicating that the structure stabilized slightly above its predicted band and eight transducers indicating that the structure stabilized within its predicted band. As the predicted bands for all measurements were significantly narrower than the respective tolerable limits, all twelve of the above measurements fell well within their tolerable

limit.

As the RA-4 internal power differs slightly from that of RA-3, the paint patterns must be modified anyway. It is presently planned to include in this modification a slight increase in painted area on the basis of the RA-3 results.

2. Solar panel temperatures were observed to stabilize at approximately 1450 F, some 23° F above the maximum predicted. This effect would result from any or all of the following three causes.

(1) Solar cells exhibit a higher absorptance of solar

energy than was thought possible.

(2) Solar cells exhibit a lower emittance of infrared

energy than was thought possible.

(3) The black paint used on the back structure of the

panels exhibit a lower emittance than was thought

possible.

It will probably not be possible to separate these three effects. Very accurate data is needed during the spacecraft pass through the earth shadow for any such calculation to be meaningful.

The remote possibility that the observed temperature measurements are due to poor thermal contact of the transducers with the panel surfaces will be removed on RA-4 by painting the front transducers white. No action directed toward lowering the panel temperatures is planned as any such action would involve major re-design of the panel

structure.

3. The gamma ray spectrometer temperature indicated a gradual climb during the entire portion of the flight before midcourse maneuver, going significantly off scale and over 40 cycles above the upper limit of its calibration. Although extrapolations of this magnitude are open to serious question, the data are undergoing detailed analysis. At present it is not possible to explain this phenomenon with any reasonable set of parameters.

Any changes to the paint pattern on the RA-4 spectrometer must be considered very carefully as they can be incorporated only at the expense of temperature stability during the terminal maneuver.

B. Extensions and Pyrotechnics

1. The following extensions were noted at the correct times:

Solar panels

Garma Ray boom

Omni-antenna

No verification of the radar altimeter extension was obtained

although the event channel was in lock at the time.

2. All squib firing event pulses were recovered except the one for midcourse motor ignition. The only abnormalities associated with any of these were the transmitter failure at the time the solar panels were extended and the lack of confirmation of altimeter extension.

There is

no data telemetered which would give any indication of what happened to

the altimeter.