Free Farmer in the Sky by Robert A. Heinlein

it. If we were going to turn mass into energy, we needed more mass with which to surround the reaction, a very special sort of mass that would not turn into energy when we didn't want it to and would hold the reaction where we wanted it. Ordinary metal wouldn't do; one might as well use soft butter.
    “But the Kilgore equations showed how to do that, too, when they were read correctly. Now has anyone here any notion of how much energy you get when you convert a chunk of mass into raw energy?”
    Nobody knew. “It's all in that one equation,” he said, “good old Doc Einstein's 'E equals M C squared.' It comes out that one gram of mass gives nine times ten to the twentieth power ergs.” He wrote it down for us: 1 gm. = 9 x l0 20 ergs.
    “Doesn't look like much, does it?” he said. “Now try it this way:” He wrote down
    900,000,000,000,000,000,000 ergs.
    “Read it off. Nine hundred thousand million billion ergs. It still doesn't mean much, does it? Figures like that are impossible to comprehend. The nuclear physicists keep a barrel of zeroes around handy the way a carpenter does a keg of nails.
    “I’ll try once more,” he went on. “A pound of mass, any old mass, say a pound of feathers, when converted into energy equals fifteen billion horsepower-hours. Does that give anyone a notion of why the Mayflower was assembled out in an orbit and will never ever land anywhere?”
    “Too hot,” somebody said.
    “'Too hot' is an understatement. If the Mayftower had blasted off from Mojave space port the whole Los Angeles Borough of the City of Southern California would have been reduced to a puddle of lava and people would have been killed by radiation and heat from Bay City to Baja California. And that will give you an idea of why the shielding runs right through the ship between here and the power plant, with no way at all to get at the torch.”
    We had the misfortune to have Noisy Edwards along, simply because he was from the same bunk room. Now he spoke up and said, “Suppose you have to make a repair?”
    “There is nothing to go wrong,” explained Mr. Ortega. “The power plant has no moving parts of any sort”
    Noisy wasn't satisfied. “But suppose something did go wrong, how would you fix it if you can't get at it?”
    Noisy has an irritating manner at best; Mr. Ortega sounded a little impatient when he answered. “Believe me, son, even if you could get at it, you wouldn't want to. No indeed!”
    “Humph!” said Noisy. “All I've got to say is, if there isn't any way to make a repair when a repair is needed, what's the use in sending engineer officers along?”
    You could have heard a pin drop. Mr. Ortega turned red, but all he said was, “Why, to answer foolish questions from youngsters like yourself, I suppose.” He turned to the rest of us. “Any more questions?”
    Naturally nobody wanted to ask any then. He added, “I think that's enough for one session. School's out.”
    I told Dad about it later. He looked grim and said, “I'm afraid Chief Engineer Ortega didn't tell you the whole truth.”
    “Huh?”
    “In the first place there is plenty for him to do in taking care of theauxiliary machinery on this side of the shield. But it is possible to get at the torch, if necessary.”
    “Huh? How?”
    “There are certain adjustments which could conceivably have to be made in extreme emergency. In which case it would be Mr. Ortega's proud privilege to climb into a space suit, go outside and back aft, and make them.”
    “You mean——”
    “Imean that the assistant chief engineer would succeed to the position of chief a few minutes later. Chief engineers are very carefully chosen, Bill, and not just for their technical knowledge.”
    It made me feel chilly inside; I didn't like to think about it.
7.    Scouting in Space
    Making a trip in a space ship is about the dullest way to spend time in the world, once the excitement wears off. There's no scenery, nothing to do, and no room to do it in.