A thermal blanket is seen on the right in flight toward a narrow miss of the ALSEP experiments. A smaller object on the left is headed in the direction of the LRRR. Frame from the 16mm DAC film taken out the LMP's window 3.25 seconds after first ascent stage motion. The blanket will impact the surface about 10-12 meters north of the Central Station at about 6.8 seconds.
(1) During final crew activities on the surface, secure or stow
debris which could be a hazard to long-term experiments or
(2) Ensure that landing areas are sufficiently far from experiment sites and structures. In the case of the Apollo LM, an adequate separation would have been something in excess of 200 m (subject top analysis of other liftoff films).
For the purposes of the following discussion, we can call the 16-mm frame showing first sustained upward displacement 'frame16-00'.
In the 16mm film, the thermal blanket is first visible at the
frame16-23, which is about 1.9 seconds after first spacecraft
Frame16-24 is the second of the 16-mm frames showing a thermal blanket flying away from the LM from the vicinity of the MESA. This frame was taken about 2.0 seconds after first spacecraft motion. Just beyond the blanket, note the edge of the continuous area of darker, disturbed lunar soil that is about 20 meters out from the MESA. See, also, pre-launch window photo AS15-88-11951.
Close examination of the 16mm film indicates that the blanket impacts the surface just north of the Central Station about 6.9 seconds after first spacecraft motion and about 5.6 seconds after the blanket's presumed launch from the MESA. The distance flown is about 110 meters, giving a ground speed of about 20 m/s. The launch elevation angle, A, is approximated by sin A = t g / 2 V where t is the time of flight (5.6 seconds), g is lunar gravity (1.62 m/s/s), and V is the ground speed (20 m/s). These values give A = 13 degrees.
Film strip of the blanket in flight. Note that the frames are not evenly spaced in time. Click anywhere on the strip for a larger version. (1) Frame16-27 (2.25 seconds) A comparison with Frame 16-24 (above) and subsequent frames in this strip shows that various tumbling motions were imparted to the blanket during launch. Because the Moon has no atmosphere, these motions will persist until impact at the ALSEP site.; (2) Frame16-29 (2.42 seconds) Note the change in blanket orientation and the separate piece of debris on the left, moving in the general direction of the LRRR; (3) Frame16-39 (3.25 seconds) The blanket has been inflight for about 2 seconds and has flown roughly 40 meters from the MESA. It's current height above the ground is about 5.75 m; (4) Frame16-60 (5.00 seconds) The blanket has been in flight for about 3.7 seconds, is about 72 meters from the MESA, and about 5.5 meters up, starting its ballistic descent; (5) Frame16-63 (5.25 seconds) Changes in LM orientation are about to take the blanket out of the field-of-view for a short time. The blanket is now about 5.1 meters above the surface; Frame 16-78 (6.5 seconds) The blanket is passing 2-3 meters north of the Heat-Flow Experiment module at a height of perhaps 1.5 meters. Note that the piece of debris flying toward the LRRR is still off the ground; (6) Frame16-82 (6.83 seconds) The impact has begun; (7) Frame16-87 (7.25 seconds) The blanket's shadow is visible again, suggesting that it is in flight again. The dark mark created during the impact is about 3 meters long and 0.5 meters wide; (8) Frame 16-90 (7.50 seconds) The blanket is definitely in flight; (9) Frame16-106 (8.82 seconds) The dark mark made during the impact seems more indistinct, suggesting that it represented shadowing by lofted dust. The LM's shadow is now in the field-of-view; (10) This frame from the 16mm film shows the final resting place of the blanket and, also, a portion of the Descent Stage.
Three TV frames have been combined to show the apparent motion of a bright patch that appears above the apparent horizon at 2.9 seconds after first spacecraft motion and reaches the righthand edge of the TV field-of-view at about 3.3 seconds. Approximate angular scales are shown on the righthand and top edges and are derived from the fact that the TV is about 160 meters from the LM and that the separation of the north and south footpads is about 11 meters. For comparison, projected positions (Xs) are given for the thermal blanket at 1.3 seconds (the presumed launch time), 2.3 and 3.3 seconds. As expected from the 13 degree launch elevation angle, the projected blanket trajectory is much shallower than that of the bright patch.