Heat Flow Experiment
.jpg?lang=en) The Apollo 17 Heat Flow Experiment on the Moon | |
| Acronym | HFE |
|---|---|
| Notable experiments | Apollo 16 & 17 |
The Heat Flow Experiment was a lunar science experiment that aimed to measure the rate of heat loss at the surface of the moon. Four experiments were carried on board Apollo missions. Two experiments were successfully deployed as part of Apollo 15 and Apollo 17. The instrument on Apollo 16 was deployed but the cable from it to the ALSEP central station was broken and the experiment was rendered inoperable. A heat flow experiment was carried on board Apollo 13 but the mission was aborted in-flight and the instrument never reached the surface.[1]
Background
Establishing some of the thermal properties of the moon's surface was already feasible by the time of the Apollo missions. Measuring of infrared emissions via telescope and the measuring of microwave emission spectra from the the moon was already possible from the surface of the earth. [2] These already has established some of characteristic of the moon's surface including temperature, thermal conductivity and heat capacity.[1] The degree to which these properties were limited by the low levels of IR emission, long wavelengths limiting data resolution, and how the moons thermal properties vary with depth.[1]
No one person can be attributed with the proposal to measure heat flow from the moon given the large number of proposals NASA sought from academia, industry and from science groups at NASA itself. Several of these proposed such an experiment.[1] The result though was that a small committee was formed to explore how thermal measurements of the moon could be taken.[1] The committee decided that the focus of any thermal experiment should be focused on heat flow from the moon's interior.[1]
The committee considered a number of approaches that included multiple probes and another that included "blankets". The blanket technique was initially ruled out due to the complexity of matching the thermal albedo of the blanket probes with that of the moon's surface.[1] The method settled on that become the basis for the instrument was a cylindrical heater paired with a temperature sensor a set distance away. [1] Further work by this group established that the probe would need to be inserted into the subsurface to avoid large temperature fluctuations caused by the day-night cycle at the surface.[1] Bendix Corporation were selected as the principal contractor for the instrument and Arthur D. Little as the sub-contractor.[1] Gulton Industries Inc. were selected to develop the electronic circuitry.[1]
Due to the need for the probe to be placed at depth below the regolith surface, it was know that a drill to penetrate the lunar surface would be required.[1] Development of the drill was lead by Martin Marietta, who had previous experience developing tools for NASA.[1]
Instrument
Missions
The heat flow experiment was originally planned to be first carried on Apollo 13 however due to the mission that occurred this did not occur. This instrument burnt up in Earth's atmosphere whilst still on board the Lunar Module.[1] There was not sufficient time to add the HFE to Apollo 14.[1]
Apollo 15
Drilling of the holes on Apollo 15 was undertaken by David Scott, the missions commander. After drilling down 100 cm, the drill started to become ineffective but despite a number of challenges Scott managed to drill down to a depth of 170 cm. By this point however Scott was having to apply his full weight and the decision was made to insert the first probe to prove out functionality.[1] A second drill hole was started but difficulties with drilling were experienced immediately and finishing of the second drill whole was delayed for the second mission EVA. The second drill hole only managed to make a depth of 100 cm and the probe was not fully below the lunar surface.[1] Despite these difficulties, the probes were able to take readings.[1]
The cause of the challenges was due to the fact that the deeper levels of the lunar soil had been undisturbed for at least half a billion years. This resulted in extreme compaction that meant further compression of the material could not occur with large amounts of force.[1]
Apollo 16
On Apollo 16 the holes for the probes were dug by Charles Duke who managed to drill down to 3 meters bellow the surface.[3] The drill on Apollo 16 had been modified to rectify the issues experienced on the prior mission, Apollo 15. The experiment came to an end before it started when John Young managed to damage the cables after getting them wrapped about his feet.[3] Whilst the cabling has been designed to resist tensile strains from being tugged, it was not designed to resist tearing motions.[1] Repairing was considered but rejected due to it needing several hours of surface time.[3]
Apollo 17
Both of the Apollo 17 boreholes were drilled without problem and both probes were installed without issue, continuing to operate for several years.[1]
Science
The failure of apollo 13 Template:Tq is only for quoting in talk and project pages. Do not use it in actual articles.
See also
References
- ^ a b c d e f g h i j k l m n o p q r s t u Langseth, M. G. (1977). "Lunar heat-flow experiment". NASA.
- ^ Clark, S. P. (1965). "Some calculations pertaining to the feasibility of measuring lunar heat flow Final report". NASA.
- ^ a b c Ulivi, Paolo; Harland, David Michael (2004). Lunar Exploration: Human Pioneers and Robotic Surveyors. Springer-praxs. p. 172. ISBN 1-85233-746-X.