Gradually the effect of the excitatory beam upon the molecules of the wall became noticeable. A spot the size of a dime began shining faintly at the point of focus of the ray-gun. It wavered uncertainly, now dimming, now brightening as Moore, strove to steady his tired arm...

The spot of brightness was now flickering into the orange-yellow and Moore knew that the melting point of the beryl-steel alloy would soon be reached. He found himself forced to watch the spot only at widely-spaced intervals and then only for fleeting moments...

Then, so suddenly that Moore did not realize it for a few moments, he was through. A tiny fissure formed at the bottom of that little pit made by the ray-gun and in less time than it takes to imagine, the churning water within had its way.

The soft, liquid metal at that spot puffed out, sticking out raggedly around a pea-sized hole. And from that hole there came a hissing and a roaring. A cloud of steam emerged and enveloped Moore.

Through the mist he could see the steam condense almost immediately to ice droplets and saw these icy pellets shrink rapidly into nothingness.

For fifteen minutes, he watched the steam shoot out.

Then he became aware of a gentle pressure pushing him away from the ship. A savage joy welled up within him as he realized that this was the effect of acceleration on the ship’s part. His own inertia was holding him back.

That meant his work had been finished — and successfully. That stream of water was substituting for the rocket blast.

(Water Tank Reaction Mass from 'Marooned off Vesta' by Isaac Asimov)

“You mean,” stammered Brandon, “that the water spout is pushing us toward Vesta; like a rocket exhaust.”

“Exactly — same thing as — rocket exhaust,” panted Moore, “action and reaction. Is located — on side opposite Vesta — hence pushing us toward Vesta.”

Shea was dancing before the porthole. “He’s right, Brandon, me boy. You can make out Bennett’s dome as clear as day. We’re getting there, we’re getting there.”

“We’re approaching in spiral path on account of original orbit,” Moore felt himself recovering. “We’ll land in five or six hours probably. The water will last for quite a long while and the pressure is still great, since the water issues as steam.”

“Steam — at the low temperature of space?” Brandon was surprised.