0' THIS is absolutely your last chance, said sign held up by technicians to Gemini 1 l's crew, Astronauts Charles Conrad and Richard Gordon. The astronauts took chance. In addition to a spacewalk, two stands, first docking maneuver ever carried out on initial orbit of a flight, and a tether maneuver in which two spacecraft whirled around each other at opposite ends of a 100-foot line, Gemini 11 set an altitude record almost three times greater than that of Soviet Union. The launch, delayed for three days, finally got off perfectly, although there were some nervous moments when an apparent cabin pressure leak was discovered. After hatch cover was resealed, leak failed to reappear, so flight got official OK. Scarcely an hour and a half after launch, Gemini II was docked with its waiting Agena target. Beautiful, said ground control. The pilot, Conrad, then pulled away from Agena and docked again. Things were going so smoothly that even Gordon had a try at it, and did perfectly. All three docking maneuvers were controlled completely from spacecraft. Charles Conrad, now a veteran astronaut, had been in space once before, on eight-day Gemini 5 flight last August, when he was co-pilot to Gordon Cooper. Gordon, however, was a rookie. Though he has been an astronaut since 1963, closest he had ever come to space before Gemini 11 was as part of back-up crew for Gemini 8. Gemini 8 was first spacecraft to dock with an Agena, though Gemini 6 and 7 had previously faced each other nose to nose in orbit. Gemini 9 rendezvoused three times with a substitute target docking adapter, but was undble to dock because clamshell doors covering docking collar failed to jettison completely. Gemini 10 was more successful, docking with one Agena and rendezvousing with another. The most spectacular part of Gemini program has been dockings, but spacewalks. Only hours before Gordon was to have stepped out of Gemini 11 for a 107-minute walk, astronauts noticed their first mechanical hitch. At 6:00 a.m. on second day in orbit, Conrad reported to ground control in Houston that No. 8 thrustor (out of 16) was not up to snuff. There are thrustors all over a Gemini spacecraft, and they have accounted for considerable trouble in past. Gemini 5 (Conrad's first flight) had thrustor problems, as did Gemini 8, which had to come down two days early because of it. Also on flight, David Scott's spacewalk was greatly curtailed due to a malfunctioning thrustor in OAMS (Orbital Attitude Maneuvering System). No. 8, a tiny rocket engine controlling role of spacecraft around its long axis, did present a critical problem since spacecraft was still locked to Agena and would remain so throughout spacewalk. Nevertheless, spacewalk had its own problems. Two flights ago, Gemini 9 spacewalker Eugene Cernan found himself virtually unable to see, due to perspiration from his body which fogged inside of his faceplate. To remedy situation, National Aeronautics and Space Administration installed a more efficient air conditoning system in suit of Gemini 10 spacewalker Michael Collins. Apparently it worked. Gordon, however, evidently found his workload greater than did Collins. The result was that perspipation running into his right eye made Gordon unable to see with it, and Conrad called him back into spacecraft rather than risk having a temporarily blind copilot on his hands. Total time elapsed: 44 minutes, instead of 107. Astronaut flight surgeon Dr. Charles Berry said that compared to some of other astronauts Gordon perspires very freely. The discovery that work may be more difficult in weightlessness of space rather than on earth came as a shock to NASA scientists, and proposals for remaining Gemini spacewalk have included ideas ranging from lightening workload to picking crew by their physical reactions to heavy work. On third day, Sept. 14, Conrad fired main engine of Agena, to which Gemini 11 was still attached, cried Whoop-de-doo, and shot up to a new record altitude of 850 miles. After exclaiming about view (just fantastic) and taking some radiation measurements, he flew spacecraft back down to a 180-mile-diameter circular orbit, where Gordon stood up on seat for 128 minutes taking pictures. Splashdown was a dream. When spacecraft landed in Atlantic, less than 21/2 miles from recovery ship, NASA described feat as the best landing we've ever had. Gemini 12's flight, tentatively set for Oct. 31, has been lengthened from three days to four, NASA officials announced after recovery of Gemini 11. However, they said decision had been made a month before. EXPERIMENTERS I