Implicit in the accomplishment of the missions we have discussed is a considerable improvement of the already substantial capabilities shown in the Apollo 11 mission. We shall enumerate a number of improvements that we think can be expected by 1972, although we should point out that the estimates are somewhat uncertain. The present capability is for a mission lasting 10.8 days, with a total of 22 hours spent on the moon; by 1972 a 16-day mission with 78 hours on the moon should be possible. The payload of scientific instruments delivered to the surface should increase from 300 to 600 pounds and the amount of material of scientific interest returned to the earth from 150 to 300 pounds. Landings, which are now limited to the equatorial zone, may be possible on most of the front face of the moon, and it may also be possible to land within 0.5 kilometer of a target area instead of within 10 kilometers as now. For men outside the lunar module the walking radius on the moon should increase from 100 meters to four kilometers, and the total distance covered during a single extravehicular activity from 500 meters to several kilometers. The capacity of the life-support pack worn by the astronauts as they move about the lunar surface may be increased by as much as 50 percent from the present 4,800 Btus. It may also be that the command module will be able, while it is in orbit around the moon, to launch a subsatellite that could make additional measurements.
These new capabilities seem within reach when considered individually. It will not be possible to have them all, because a few are mutually exclusive. For example, if it were decided to land a 600-pound load of scientific instruments on the moon, it probably would not be possible to equip the astronauts to traverse as much as 10 kilometers of the lunar surface.
It also seems probable that a constant-volume suit will be available for lunar astronauts soon. With the present variable-volume suit the astronaut has to do a considerable amount of work against the suit. He also cannot bend his waist or his ankles. The constant-volume suit will require about 30 percent less work for equivalent tasks because almost no work will have to be done against the suit. It will also be flexible at the waist and the ankles. With this suit the astronaut should have considerably more mobility on the lunar surface.
Even so, several of the sites we have discussed cannot be explored adequately unless the astronauts have more mobility than walking provides. Indeed, the radius of mobility ought to be about 30 kilometers from the landing site. Obviously a vehicle will be needed. Two approaches are possible: the vehicle could crawl along the lunar surface at a few miles per hour or it could fly over the surface at low altitude. The ground vehicle has the advantage of enabling the occupants to stop and look at interesting objects, whereas a rocket-powered flying platform makes it possible to move rapidly from one point of major interest to another. A flying vehicle could also move vertically, as will be desirable at certain lunar sites. Although both flying and crawling vehicles have distinct advantages, both are expensive, and it may well be that only one capability will be developed.
Inasmuch as the most that can be expected of a landing party is the exploration of 10 to 100 square kilometers in the vicinity of the landing site, the nine additional landings now planned will cover only about one part in 10,000 of the front face of the moon. In order to obtain a more comprehensive picture of the surface, including the far side, and to look for classes of features missed at the landing sites, NASA plans to use instruments mounted in the service module for remote sensing from orbit. The sensors will be put into service starting at about the sixth landing.