[X] My Assistant

[GregM]

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[dvandorn]

The Apollo deep cores were retrieved using segmented tubes. There was an initial "long tube" that was just under a meter long, and IIRC three extensions of about 30 to 40 cm each that were screwed onto the previous tube segment.

Because the suits were so stiff it was difficult to drill the tube completely into the ground, with the drill head going down to surface level, a total of about 2.5 meters of tube were provided, but the deepest core was just more than 2 meters deep.

There was one point at which you *did* see the crews carrying around a 2.5-meter tube, though -- when they extracted the cores from the ground. The whole tube, all four pieces, was pulled out of the ground and then unscrewed into its constituent segments. This provided some serious difficulty on Apollo 15, as well, and they ended up returning the long tube and the three extensions as two separate units, as opposed to breaking them all down into their individual segments. (And yes, these cores were returned in bags, exposed to the crew air environment, as opposed to being placed inside sealed vacuum containers. They wouldn't fit inside the SRCs.)

The heat flow probes were emplaced in a similar fashion, by attaching a succession of hollow tubes to the drill. However, the heat flow probes were simply placed directly into the hollow drill stems (which, for the heat flow holes, were *not* open at the pointy end). Thus there was never a question of the physical surroundings of the heat flow probe, and there was never the possibility of a drilled hole collapsing before the probe was inserted.

Interestingly, the way the drill was designed, you had to drill your heat flow holes first and *then* drill the deep core sample. The heat flow drill stems attached to the drill slightly differently than the sample tubes, to allow for the pushback of material filling the sample tubes. Once you attached a sample tube to the drill, you couldn't use it to drill heat flow stems into the ground. This was a specific concern on Apollo 16, where the HFE electronics box was torn from its cable after the first heat flow hole was drilled, but before the second hole had been drilled. Charlie Duke went on to drill the core sample, and was reminded that he couldn't drill another heat flow hole after he did this. He responded that, if they could by some miracle fix the HFE electronics cable, he was simply planning on trying to drop the second probe into the deep core sample hole.

On all of the missions that included the HFE (four in all, although it was only deployed successfully on two), the alternate plan in case the drill failed was to dig a long trench and bury the probes lengthwise... which never made a lot of sense to me.

-the other Doug