'Then get on with it - and bear in mind you are a crew member in space.'
'Aye aye, sir.'
He had in fact 'picked the easy one'; the basic tack-around-Earth-for-Mars problem had been solved by the big computers of Luna Pilot Station before they blasted off. To be sure, Luna Pilot's answer would have to be revised to fit the inevitable errors, or deviations from flight plan, that would show up when they reached perigee rounding Earth - they might be too high, too low, too fast, too slow, or headed somewhat differently from the theoretical curve which had bem computed for them. In fact they could be sure to be wrong in all three factors; the tiniest of errors at blast-off had a quarter of a million miles in which to multiply.
But nothing could be done to compute the corrections for those errors for the next fifteen or twenty hours; the deviations had to be allowed to grow before they could be measured accurately.
But the blast back to shape an ellipsoid home to Luna was a brand-new, unpremeditated problem. Captain Stone had not refused it out of laziness; he intended to do both problems but had kept his intention to himself. In the meantime he had another worry; strung out behind him were several more ships, all headed for Mars. For the next several days there would be frequent departures from the Moon, all ships taking advantage of the one favorable period in every twenty-six months when the passage to Mars was relatively 'cheap', i.e., when the minimum-fuel ellipse tangent to both planet's orbits would actually make rendezvous with Mars rather than arrive foolishly at some totally untenanted part of Mars' orbit. Except for military vessels and super expensive passenger-ships, all traffic for Mars left at this one time.
During the four-day period bracketing the ideal instant of departure ships leaving Leyport paid a fancy premium for the privilege over and above the standard service fee. Only a large ship could afford such a fee; the saving in cost of single-H reactive mass had to be greater than the fee. The Rolling Stone had departed just before the premium charge went into effect; consequently she had trailing her like beads on a string a round dozen of ships, all headed down to Earth, to tack around her toward Mars.
If the Rolling Stone vectored back and shaped course for Luna rather than Mars, there was a possibility of traffic trouble.
Collisions between spaceships are almost unheard of; space is very large and ships are very tiny. But they are possible, particularly when many ships are doing much the same thing at the same time ia the same region of space. Spacemen won't forget the Rising Star and the patrol vessel Trygve Lie - four hundred and seven dead, no survivors.
Ships for Mars would be departing Luna for the next three days and more; the Rolling Stone, in rounding Earth and heading back to Luna (toward where Luna would be on her arrival) would cut diagonally across their paths. Besides these hazards, there were Earth's three radio-satellites and her satellite space station; each ship's flight plan, as approved by Luna Pilot Station, took into consideration these four orbits, but the possible emergency maneuver of the Rolling Stone had had no such safety check. Roger Stone mentally chewed his nails at the possibility that Traffic Control might refuse permission for the Rolling Stone to change its approved flight plan - which they would do if there was the slightest possibility of collision, sick child or no.
And Captain Stone would ignore their refusal, risk collision and take his child home - there to lose his pilot's license certainly and to face a stiff sentence from the Admiralty court possibly.
Besides the space station and the radio satellites there were the robot atom-bomb peace rockets of the Patrol, circling the Earth from pole to pole, but it was most unlikely that the Rolling Stone's path would intersect one of their orbits; they moved just outside the atmosphere, lower than a spaceship was allowed to go other than in landing, whereas in order to tack the Rolling Stone would necessarily go inside the orbits of the radio satellites and that of the space station wait a minute - Roger Stone thought over that last idea. Would it be possible to match in with the space station instead of going back to Luna?
If he could, he could get Lowell back to weight a couple of days sooner - in the spinning part of the space station!
The ballistic computer was not in use; Castor and Hazel were still in the tedious process of setting up their problems. Captain Stone moved to it and started making a rough set-up directly on the computer itself, ignoring the niceties of ballistics, simply asking the machine, 'Can this, or can this not, be done?'
Half an hour later he gave up, let his shoulders sag. Oh, yes, he could match in with the space station's orbit - but at best only at a point almost a hundred degrees away from the station. Even the most lavish expenditure of reaction mass would not permit him to reach the station itself.
He cleared the computer almost violently. Hazel glanced toward him. 'What's eating you, son?'
'I thought we might make port at the station. We can't.'
'I could have told you that'
He did not answer but went aft. Lowell, he found, was as sick as ever.
Earth was shouldering into the starboard port, great and round and lovely; they were approaching her rapidly, less than ten hours from the critical point at which they must maneuver, one way or the other. Hazel's emergency flight plan, checked and rechecked by the Captain, had been radioed to Traffic Control. They were all resigned to a return to Luna; nevertheless Pollux was, with the help of Quito Pilot, Ecuador, checking their deviations from the original flight plan and setting up the problem of preparing a final ballistic for Mars.
Dr Stone came into the control room, poised near the hatch, caught her husband's eye and beckoned him to come with her.
He floated after her into their stateroom. 'What is it?' he asked. 'Is Lowell worse?'
'No, he's better.'
'Eh?'
'Dear, I don't think he was spacesick at all.'
'What's that?'
'Oh, a little bit, perhaps. But I think his symptoms were largely allergy; I think he is sensitive to the sedative.'
'Huh? I never heard of anyone being sensitive to that stuff before.'
'Neither have I, but there can always be a first time I withdrew the drug several hours ago since it did not seem to help him. His symptoms eased off gradually and his pulse is better now.'
'Is he okay? Is it. safe to go on to Mars?'
'Too early to say. I'd like to keep him under observation another day or two.'
'But - Edith, you know that's impossible. I've got to maneuver.' He was wretched from strain and lack of sleep; neither had slept since blast-off more than twenty-four hours earlier.
'Yes, I know. Give me thirty minutes warning before you must have an answer. I'll decide then.'
'Okay. I'm sorry I snapped at you.'
'Dear Roger!'
Before they were ready to 'round the corner' on their swing past Earth the child was much better. His mother kept him under a light hypnotic for several hours; when he woke from it he demanded food. She tried letting him have a few mouthfuls of custard; he choked on the first bite but that was simply mechanical trouble with no gravity - on the second bite he learned how to swallow and kept it down.
He kept several more down and was still insisting that he was starved when she made him stop. Then he demanded to be untied from the couch. His mother gave in on this but sent for Meade to keep him under control and in the bunk-room. She pulled herself forward and found her husband. Hazel and Castor were at the computer; Castor was reading off to her a problem program while she punched the keys; Pollux was taking a doppler reading on Earth. Edith drew Roger Stone away from them and whispered, 'Dear, I guess we can relax. He has eaten - and he didn't get sick.'
'Are you sure? I wouldn't want to take even a slight chance.'
She shrugged. 'How can I be sure? I'm a doctor, not a fortune-teller.'
'What's your decision?'
She frowned, 'I would say to go on to Mars.'
'It's just as well.' He sighed. 'Traffic turned down my alternate flight plan. I was just coming back to tell you.'
'Then we have no choice.'
'You know better than that. I'd rather tell it to the judge than read the burial service. But I have one more card up my sleeve.'
She looked her query; he went on. 'The War God is less than ten thousand miles behind us. If necessary, by using our mass margin, in less than a week I could match with her and you and the baby could transfer. She's a "tumbling. pigeon" since they refitted her - anything from Luna-surface to a full gravity.'
'I hadn't thought of that. Well, I don't think it will be necessary but it's a comfort to know that there is help close by.' She frowned. 'I would not like to leave you and the children to shift for yourselves - and besides, it's risky to use your margin; you may need it badly when we approach Mars.'
'Not if we handle the ship properly. Don't you worry; Hazel and I will get it there if we have to get out and push.'
Pollux had stopped what he was doing and had been trying to overhear his parents' conversation. He was unsuccessful; they had had too many years' practice in keeping the kids from hearing. But he could see their intent expressions and the occasional frowns; he signaled his twin.
Castor said, 'Hold it, Hazel. Time out to scratch. What goes, Pol?'
"'Now is the time for all good men".' He nodded toward their parents.
'Right. I'll do the talking.' They moved aft.
