'All right, Boyd,' he said, 'I'll take care of this. But if I do, you are going to have to stop calling me "Doc"'
'Yes, sir,' the computerman said, straightening up and saluting. 'I understand, Captain.'
'You sent for me, sir?'
Don looked up and saw Chief Petty Officer Kurikka at the entrance to the wardroom. He waved him forward.
'Come in, Chief. I'm having a meeting in about half an hour, but I wanted to talk to you first. If anyone is able to answer my questions about the Johannes Kepler, you should be the one.' He pointed to the model of the spacer on the table before him. 'I understand that you have been aboard this ship since she was commissioned?'
'Longer than that, sir. I was in the construction gang that assembled the Big Joe in Earth orbit. I switched to the space service then and stayed aboard her.'
With his fair hair and blue eyes the tall Finn did not show his years at all.
'Better than I thought,' Don said. 'Do you think you could explain to me about the precession and wobble that has the computermen so worried?'
Kurikka nodded, and carefully unfastened the model of the ship from its base and held it before him.
'The way they described the Big Joe to us when we were building her is the best way I know. It's a bass drum hooked to a basketball by a gaspipe.'
'You're right - once you hear that you can't forget it.'
'The gaspipe passes through the heads of the drum, with a little sticking out on one side, and all the rest of it on the other. The basketball is on the end of the long chunk of pipe. In the ball is the atomic reactor and the engines. Where the ball is hooked to the pipe is all the radiation insulation and the engine-room. Everything else in the ship is in the drum.
When we are in orbit the whole ship rotates round the main axis of the pipe -which is called the midpipe.'
'I'm with you so far,' Don said, and tapped the drum with his finger. And the drum rotates so fast that the centrifugal force generates the equivalent of one gravity here on A deck. A deck is the first deck in and, like all the decks, goes all the way around the drum. The floor under our feet is the outside skin of the ship. We go up one flight, "up" really being in towards the centre of rotation, to В deck. Then to C deck, which is cargo and storage only, and the last pressurized deck. The interior of the drum is open to space and is for cargo only. Am I right so far?'
'In the green, sir.' Kurikka's impassive face almost bent into a smile, but not quite.
Don spun the pipe between his hands so that the model rotated, and, at the same time, aimed the drum at the light above the table.
'So here is the ship in flight, spinning as she goes. And aiming at that light which well call Mars.'
'That's not quite right, sir. After takeoff and flame-out the ship was flipped end for end, so our main jets are now pointed at Mars. The observatory, back here where the stub of pipe sticks through the drum, is pointed back the way we came.'
Don turned the model end for end and examined it. 'So this is the way we are moving - and spinning at the same time. Then what is wrong?'
The Chief pointed. 'The axis of rotation of our midpipe should be right on line with our course. In that way jets fore or aft can speed us up or slow us down in orbit. We get to the same spot, but we get there sooner or later. Or if course change is needed the lateral jets, here on the centre of balance on the mid-pipe, can alter our course sideways in any degree that is needed. None of that is possible now.'
'Why?'
'Because the meteorite started the axis of our rotation shifting. Were no longer pointing straight down the orbit, and the change is continuing. Its a mighty slow tumble, but that's just what it is. We're tumbling along through space. We can't make any course corrections until we can straighten out the tumble.'
'And unless we do make the course corrections we're going to miss Mars completely.'
With slow seriousness, Chief Kurikka nodded agreement. The long silence that followed was broken by a brisk rapping on the wardroom door. The Chief went over and opened it. Computerman Boyd was outside. '03-00 hours, Captain,' he said. 'The Purser is here with me and Commander Holtz said to tell you he'll be along shortly'
'Come in then. We can get started without him.'
They entered the wardroom - followed by a man whom Don had never seen before. He had straight black hair, now greying, a great flowing moustache and coppery skin. One of the passengers, obviously - but what was he doing here? Before Don could ask the obvious question the Purser, Jonquet, stepped forward. He was Swiss, and had been trained as a hotel manager. So that, even after years in space, he still carried the feeling of a grand hotel about him. He made what could only have been a slight bow and indicated the man with him.
'I hope you will excuse me, Captain, but I have taken the liberty of bringing someone to this assembly whom I wish you to meet. This is Doctor Ugalde, of the University of Mexico. He is one of the foremost mathematicians in the world. I thought that his voice lowered - 'with the death of the other officers, Doctor Ugalde might be able to supply us with aid of importance.'
Don could not be angry. Of course the Purser had no business making decisions without asking him first. But he, a doctor of medicine, had no business acting like a captain. The two cancelled out.
'Thank you,' Don said. 'It was a good idea that I should have thought of myself. Since mathematics seem to be at the core of our problem.'
'Do not expect too much!' Ugalde said, waving his hands excitedly. 'Between the airy heights of abstract mathematics and the practicalities of flying a spaceship is a universe of difference. I have no experience ...'
'None of us has the experience we need,' Don broke in. 'We are going to have to feel our way along, so we can certainly use your help, Doctor. I ask only that you do not reveal to the other passengers how many officers have been killed and what a plight we are in.'
'My word of honour!' Ugalde said, standing up straight and placing his hand over his heart. 'My noble ancestors fought for the freedom of my country and many of them died in its cause. I can do no less.'
Don could not quite see the connection between this and their present danger, but he nodded agreement nevertheless, and asked them all to be seated. Then he explained their problem and the difficulty of correcting it without the skilled knowledge of the dead officers.
'That's the picture,' he concluded, 'and it's not good. Boyd, what's the usual drill in a course correction?'
The computerman chewed his lip and looked around nervously.
'I can't really say, sir. The astrogator would give me the figures already processed for the computer, and I wouldn't do much more than check for transcription errors and feed them into the machine. Sometimes, on complex problems, we would send the figures to Mars Central. They have bigger computers there and staff mathematicians.' His eyes widened at a sudden idea. 'Say, couldn't we do that? Get help by radio, I mean?'
Don shook his head sadly.
'We can't do that - and I don't want that information to leave this room. The main transceiver has been knocked out. The radio operator is jury-rigging a transmitter and receiver. But we don't know how long it will take him - or how powerful they will be when he is finished. So, at least for the moment, we have to forget about outside aid.' He turned to the mathematician. 'Can you help us with this problem?' he asked.
Dr Ugalde stood up instantly and began to pace the floor, one hand behind his back. He seemed to think better this way. 'Impossible, impossible,' he said.
Astrogation as an applied science is a world removed from theoretical mathematics. I know nothing of the forces and measurements involved. A three body problem, of course, that is not difficult. But...'