Looked at that way, rockets shouldn't push
hard in a Dabney field. There oughtn't to be any gain to be had by the
field at all. You see?"
Cochrane fumbled in his head.
"Oh, yes. I thought of that. But there is an advantage. The ship does
work."
"Because," said Jones, triumphant again, "the field-effect depends
partly on temperature! The gases in the rocket-blast are hot, away up in
the thousands of degrees. They don't have normal inertia, but they do
have what you might call heat-inertia. They acquire a sort of fictitious
mass when they get hot enough. So we carry along fuel that hasn't any
inertia to speak of when it's cold, but acquires a lunatic sort of
substitute for inertia when it's genuinely hot. So a ship can travel in
a Dabney field!"
"I'm relieved," acknowledged Cochrane. "I thought you were about to tell
me that we couldn't lift off the moon, and I was going to ask how we got
here."
Jones smiled patiently.
"What I'm telling you now is that we can shoot rocket-blasts out of the
Dabney field we make with the stern of the ship! Landing, we keep our
fuel and the ship with next to no mass, and we shoot it out to where it
does have mass, and the effect is practically the same as if we were
pushing against something solid! And so we started off with fuel for
maybe five or six landings and take-offs against Earth gravity.
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