They waited again and, instead of the course corrections, they received a request for the amount of reaction mass that remained in their tanks. This was sent back as quickly as possible and there were minutes of silence as they waited for the answer, for the corrections that would get them back into the proper orbit for Mars. The message finally came.
'Hello Big Joe,' the voice rasped and, although the man speaking tried to sound happy, there was an undertone of worry in his voice. 'We are not saying that this is the final answer, the figures are being re-run, and something will be done. But the truth is... well... you have been in an incorrect orbit for too long a time. It appears that, with the reaction mass you have remaining... there is not enough to make a course correction for Mars. Your ship is on an unchangeable orbit into outer space.'
In the silence that followed this shocking announcement, the rapping on the control-room door sounded unnaturally loud. An air tenders mate came in and saluted, throwing a quick glance around at the silent men. He handed a slip of paper to Don.
'I thought I had better bring these readings directly to you, sir. I just ran the test a few minutes ago.'
Don stirred himself, it took an effort to think of other problems after what they had just heard. He took the slip and looked, uncomprehending, at the piece of paper.
I'm sorry, could you tell me what these figures mean?'
The air tender pointed to the row of numbers on the right, and to the last one which was circled in red.
'These are the percentages of oxygen concentration in the air. You'll notice they have been going down steadily. These are the figures taken every five hours, since the accident. The change has been slow, but there is now an abrupt drop, here in the last number. I think the radiation from the solar storm knocked out a lot of phytoplankton. That, in addition to what we lost with the water, is putting us below equivalency.'
'What does that mean?'
'Well, simply, sir, the people in the ship are turning oxygen into carbon dioxide faster than the plants can replace the oxygen. We're running out of breathable air.'
Don shook himself. There were too many problems at once.
'How long before it reaches the danger level?' he asked.
'Days at least, I'm not sure. But something should be done now...'
'Not at the present moment. I'll be down to air control as soon as I can. Who is in charge?'
The crewman, he could not have been over twenty years old, looked uncomfortable. 'Well, Lieutenant Hong is dead, so I guess that leaves me.'
'What's your name?'
'Hansen, Air Tenders Mate 3rd Class Hansen.'
'All right, Hansen, you are now acting air control officer. Do your work well because we all depend upon you.'
'Yes, sir,' Hansen said, squaring his back and saluting.
He'll do the job, Don thought, watching the man leave. Then memory of the message from Mars returned, and with it a feeling of sick depression. He returned to Kurikka.
'What is this reaction mass that Mars Central is so worried about?' he asked. 'I hate to act stupid, but medical studies leave little time for reading about anything else. I thought this ship was powered by atomic engines ?'
'It is, sir, but we still need reaction mass. A rocket moves not by pushing against anything, but by throwing something away. Whatever is thrown away is called reaction mass. In chemical rockets it is burning gas. The gas goes in one direction, the rocket goes in the other. The more you throw away, the more reaction you get and the faster you go. You also get more reaction by throwing something away faster. That is what we do. Our reaction mass is made up of finely divided particles of silicon. It's made from steel plant slag, vaporized in a vacuum, so the particles are microscopic. These particles are accelerated by the engines to an incredible speed. That's what gives us our push.'
Don nodded. 'Seems simple enough -at least in theory. So, although we have unlimited power from the atomic engines, we don't have enough reaction mass for the course change required?'
'Right, sir. Normally we carry more than enough mass for our needs, because the course corrections are made as early as possible. The more the ship gets away from the right orbit, the more mass is needed to get us back. We've waited a little too long this time.'
Don refused to give in to the feeling of gloom that swept the control-room.
'Can't we use something else for reaction mass?' he asked.
Kurikka shook his head. 'I'm afraid not. Nothing is small enough to get through the injectors. And the engines are designed to run with this kind of reaction mass only.' He turned away and, for the very first time, Don saw that the rock-like chief petty officer was feeling defeat. 'I'm afraid there is nothing we can do.'
'We cant give up!' Don insisted. 'If we can't change the orbit to the correct one, we can certainly alter it as much as possible, get it closer to the correct one.'
'Maybe we can, Captain, but it won't help. With all our mass used to change course we won't have enough for deceleration.'
'Well at least we'll be closer to Mars. There must be other ships there that can match orbits with us and take everyone off. Let's ask Mars Central about it.'
The answer was infuriatingly slow in coming, and not very hopeful.
'We are running all the possibilities through the computer here, but there is nothing positive yet. There are no deep-spacers here who can aid you, and the surface to satellite ferries don't have the range to reach you, even with your correct orbit. Don't give up hope, we are still working on the problem.'
'Great lot of good that does us,' Sparks muttered. 'You're not in our shoes'
'I am afraid I must disagree with Chief Kurikka and say that his last statement is wrong,' Ugalde said. He had been standing in a daze of concentration for a long time, and did not realize that the Chief's last' statement had been spoken almost fifteen minutes earlier. 'There is something we can do. I have examined the situation from all sides and, if you will permit me to point out, you are looking at only part of the problem. This is because you have stated the question wrong.' He began to pace back and forth.
'The problem is to alter our orbit to the correct one, not to find more mass. Stated this way the problem becomes clear and the answer is obvious.'
'Not to me,' Kurikka said, speaking for all of them.
Ugalde smiled. 'If we cannot get more reaction mass, then we must get less mass for our present quantity of reaction mass to work against.'
Don smiled back. 'Of course! Ihats it! We will just have to lighten ship.'
'It is important that everything that is jettisoned be weighed first,' Ugalde warned. 'This will be needed in the computations. And the faster it is done the better our chances will be!'
'We start right now,' Don said, pulling over a notepad and electric stylo. 'I want to list everything that is not essential to the operation of the ship and the lives of everyone aboard. Suggestions?'
'The passengers' luggage of course,' Ugalde said. They should keep what they are wearing and the rest will be discarded.'
The purser moaned. 'I can see the lawsuits already.'
'I'm sure that the company is insured,' Don said, making a note. 'Their luggage or their lives - that is really not much of a choice. They can keep their valuables and personal items, but anything that can be replaced has to go. You'd better have them all assembled in the main dining-hall in fifteen minutes. I'll come up and tell them myself'
Jonquet nodded and left. Don turned to the others.
'The dining-tables, chairs, dishes, most of the kitchen equipment,' Kurikka said, counting off the items on his fingers. 'All the frozen meat and refrigerated food. We can live off the dehydrated emergency rations which use recycled water.'