PI/Engineer: Robert L. Kovack, Stanford Univ.
Other Contacts: Joel S. Watkins, UT-Galveston; Pradeep Talwani, Stanford Univ.
Apollo Flight Nos.: 17
Apollo Exp't No. S 203
Discipline: lunar seismometry
Weight: 25.1 kg, total; 7.1 kg geophones, 17.6 kg explosives
Dimensions: several packages - see reference
This is an extension of the Active Seismic Experiment carried on A-14 and 16. The data were planned to determine the internal characteristics of the lunar crust to a depth of several kilometers. Eight explosive charges (containing from 57 to 2722 g of high explosive) were deployed at distances between 100 m and 3.5 km from an array of 4 identical geophones. These charges were later detonated by a timer after LM ascent stage lift-off, and seismic measurements were obtained. The electronics for the experiment were one of the ALSEP packages. A whip antenna was deployed near the HFE which sent the signals to these charges. For stability, the antenna was mounted to the subpallet to which the HFE had been mounted for transport.
Unloading from the LM: As part of ALSEP.
Transporting by foot or MET: The geophones were carried as part of the ALSEP.
Loading/unloading tools/exp'ts on LRV:
The explosive charges were carried on the traverses for deployment at distant sites - see figure for placement on the LRV. No particular hazards or problems were encountered.
The geophone array was part of the ALSEP on A-17. Explosive charges were placed at distant locations while on field geology traverses. Charges deployed within line-of-site of the ASLEP were deployed in shallow depressions.
Operations were spread out over the 3 EVAs. The ALSEP electronics module containing the 4 geophones was deployed on EVA 1 without difficulty. The timeline allotted 29 minutes to deploy and photograph them. Two explosive packages were also deployed on the 1st EVA, 3 on 2nd EVA, and 3 on EVA 3. See "hazards" for arming sequence of the explosive package. The packages needed to be in the sun to ensure temperatures above 5deg C before activation. Also, each explosive package had to have a telescoping antenna pulled out.
Check-out of experiment: from Earth
Operation of experiment:
From JSC via the ALSEP command system. The explosive charges were set off after the crew left. Also, the crash of the ascent stage of the LM was recorded. High and low scan rates could be selected.
Repairs to experiment: NA
Recovery/take-down of experiment: NA
Stowing experiment for return: NA
Loading/unloading samples on LRV:
There were temperature requirements on the timers in the explosive packages that constrained LRV operations in the shade.
Loading of exp't/samples into the LM: NA
Stowing of package once in the LM: NA
Sampling operations - soil, rocks: NA
Navigating/recognizing landmarks: NA
Were there any hazards in the experiment?
i.e. hazardous materials (explosive, radioactive, toxic), sharp objects, high voltages, massive, bulky, tripping hazards, temperatures?
Explosive charges were used for active sounding. These were deployed by the crew while on traverses, but not activated until after departure. All 8 were fired. An explosive package was activated by removing 3 pull pins. Removal of the 1st pin activated the SAFE/ARM slide timer, which was preset at ~90 hours (each one varied slightly). Removal of the second pull pin released the SAFE/ARM slide from its constrained SAFE position. Removal of the 3rd pin removed a constraint on the firing pin and activated the thermal battery timer. The LSPE transmitter, which was located on the ALSEP central station, transmitted a repetitive pulsed carrier signal. A series of 3 pulses properly spaced in time was required to elicit a FIRE signal from the signal processor within the explosive package and to detonate the explosives train. The thermal battery, activated by the timer, had a minimum life of 2 min., ensuring that at least 1 firing pulse set was received while the explosive package was energized electrically. One of the explosions was seen via TV by using the camera of the LRV after departure of the crew.
There was concern late in the A-17 mission planning when someone raised the possibility that the larger charges could conceivably throw debris to altitudes where the CSM was still gathering orbital data two days later. Although it was a remote possibility, the idea of "shooting down" the last mission after it had successfully landed and returned to orbit did not sit well with NASA Headquarters. After a hastily convened group of explosive (Bureau of Mines, NRL, and others) and cratering/impact experts met it was calculated that the risk was in the range of 10^-5 to 10^-6, which was good enough to allow the experiment to proceed.
Was lighting a problem? No.
Were the results visible to the crew? No.
Would you recommend any design changes? No comments by crew.
Were any special tools required? No, although the LRV was used to deploy the charges.
Was the orientation of the experiment (i.e. horizontal/vertical) important? Difficult?
The arrangement of the geophones was planned to gather seismic signals.
Was the experiment successful? Yes.
Were there related experiments on other flights?
See S 033, Active Seismic Experiment, on A-14 and A-16. See also S 031 - Passive Seismic Experiment (Package).
Where was it stored during flight?
Explosive packages stored in Quad III in 2 groups of four. The rest of the unit was in Quad IV on the MESA.
Were there any problems photographing the experiment? No.
What pre-launch and cruise req'ts were there?
power, thermal, late access, early recovery?
What was different between training and actual EVA? No comments by crew.
What problems were due to the suit rather than the experiment? No comments by crew.
Any experiences inside the LM of interest from the experiment/operations viewpoint?
No comments by crew.
A-17 Preliminary Science Report
Apollo 17 Mission Report
Apollo 17 Final Lunar Surface Procedures, Vol. 1: Nominal Plans, MSC, 11/6/72
Apollo Lunar Surface Experiments Package - Apollo 17 ALSEP (Array E) Familiarization Course - Handout for class of 1 September 1972, in JSC History Office
Apollo Scientific Experiments Data Handbook, JSC-09166, NASA TM X-58131, August, 1974, In JSC History Office.
Apollo Program Summary Report, section 3.2.11 Lunar Seismic Profiling Experiment, JCS-09423, April, 1975.
ALSEP Array E Critical Design Review Presentation Material, NASA/MSC - Bendix Aerospace Systems Division, NAS9-5829, 14 - 18 June 1971, in JSC History Office.
Personal communication, Jack Sevier to Tom Sullivan, 18 May 1993.