Arcot had been afraid his father would be worried about that, so he framed his explanation carefully. "Dad, we figured this ship out to the last decimal place; it's the best we can make it. Remember, the molecular motion drive will get a trial first; we'll give it a trial trip when we leave the sun. If there's any trouble, naturally, we'll return. But the equipment is standard, so we're expecting no trouble.
"The only part that would require a trial trip is the space-control apparatus, and there's no way to give that a trial trip. Remember, we have to get far enough out from the sun so that the gravitational field will be weak enough for the drive to overcome it. If we tried it this close, we'd just be trying to neutralize the sun's gravity. We'd be pouring out energy, wasting a great deal of it; but out away from the sun, we'll get most of the energy back.
"On the other hand, when we do get out and get started we will go faster than light, and we'd be hopelessly beyond the range of the molecular motion drive in an instant. In other words, if the space-control drive doesn't work, we can't come back, and if it does work, there's no need to come back.
"And if anything goes wrong, we're the only ones who could fix it, anyway. If anything goes wrong, I'll radio Earth. You ought to be able to hear from me in about a dozen years." He smiled suddenly. "Say! We might go out and get back here in time to hear ourselves talking!
"But you can see why we felt that there was little reason for a trial trip. If it's a failure, we'll never be back to say so; if it isn't, we'll be able to continue."
His father still looked worried, but he nodded in acquiescence. "Perfect logic, son, but I guess we may as well give up the discussion. Personally, I don't like it. Let's see this ship of yours."
The great hull was two hundred feet long and thirty feet in diameter. The outer wall, one foot of solid lux metal, was separated from the inner, one-inch relux wall by a two inch gap which would be evacuated in space. The two walls were joined in many places by small lux metal cross-braces. The windows consisted of spaces in the relux wall, allowing the occupants to see through the transparent lux hull.
From the outside, it was difficult to detect the exact outline of the ship, for the clear lux metal was practically invisible and the foot of it that surrounded the more visible part of the ship gave a curious optical illusion. The perfect reflecting ability of the relux made the inner hull difficult to see, too. It was more by absence than presence that one detected it; it blotted out things behind it.
The great window of the pilot room disclosed the pilot seats and the great switchboard to one side. Each of the windows was equipped with a relux shield that slid into position at the touch of a switch, and these were already in place over the observatory window, so only the long, narrow portholes showed the lighted interior.
For some minutes, the elder men stood looking at the graceful beauty of the ship.