Nagel was becoming perturbed over their oxygen consumption. He had set up the small tanks containing algae in a nutrient solution, tending them like a mother hen. In time, if the cultivation were successful, the small algae farm would convert the carbon dioxide from their respiration into oxygen. At the present time the carbon dioxide was being absorbed by chemical means. As things stood, it was necessary for the entire crew to don spacesuits every time one of them left the cabin. Each time the cabin air was lost in the vacuum of the moon. Crag pointed out there was no alternative until the airlock was completed, a fact which didn't keep Nagel from complaining. * * * * * Otto Richter recovered fast. Before another day had passed--the Aztec continued to operate by earth clock--he seemed to have completely recovered. It was evident that concussion and shock had been the extent of his injuries. Crag didn't know whether to be sorry or glad, he didn't, in fact, know what to do with the man. He gave firm orders that Richter was never to be left alone--not for a moment. He told him: "You will not be allowed in the area of any of the electronic equipment. First time you do ..." He looked meaningfully at him. "I understand," the German said. Thereafter, except for occasional trips to the commode, or to help with work, he kept to the corner of the space cabin allotted him. Larkwell came up for the evening meal wearing a grim look. He extended his hand toward Crag, holding a jagged chunk of rock nearly the size of a baseball. Crag took the hunk and hefted it thoughtfully. "Meteorite?" The others clustered around. "Yeah. I saw a hole in that cleared off section and reached down. There she was, big as life." "If that had hit this pipe we'd be dead ducks," Prochaska observed. "But it didn't hit," Crag corrected, trying to allay any gathering nervousness. "It just means that we're going to have to get going on the rill airlock as soon as possible." "How will loss of Able affect that?" Nagel asked curiously. "Only in the matter of size," Crag explained. "The possible loss of a drone was taken into account. The plastiblocks are constructed to make any size shelter possible. We'll start immediately when Baker lands." He looked thoughtfully at the men. "Let's not borrow any trouble." "Yeah, there's plenty without borrowing any more," Prochaska agreed. He smiled cheerfully. "I vote we all stop worrying and eat." Another complication arose. Drone Baker would be in orbit the following morning. Prochaska had to be prepared to bring it down. He was busy moving his equipment into one compact corner opposite the commode. He rigged a curtain around it, partly for privacy but mainly to mark off a definite area prohibited to Richter.