The Mote in God's Eye

Blaine fiddled with his screen controls to produce a 3-d graph overhead. He cut in the privacy switch to hide his doodles from the rest of the crew. Around him the bridge officers attended to their duties, Cargill and Sailing Master Renner huddled together near the astrogation station, Midshipman Staley settled next to the helmsman ready to assist if needed but mostly there to learn how to handle the ship. Blaine’s long fingers moved over the screen controls.

A long green velocity line, a short lavender vector pointing in the opposite direction—with a small white ball between. So. The intruder had come straight from the direction of the Mote and was decelerating directly into the New Cal system… and it was somewhat bigger than Earth’s Moon. A ship-sized object would have been a dimensionless point.

A good thing Whitbread hadn’t noticed that. There’d be gossip, tales to the crew, panic among the new hands… Blaine felt the metallic taste of fear himself. My God, it was big.

“But they’d have to have something that big,” Rod muttered. Thirty-five light years, through normal space! There never had been a human civilization that could manage such a thing. Still—how did the Admiralty expect him to “investigate” it? Much less “intercept” it? Land on it with Marines?

What in Hannigan’s Hell was a light sail?

“Course to Brigit, sir,” Sailing Master Renner announced.

Blaine snapped up from his reverie and touched his screen controls again. The ship’s course appeared on his screen as a pictorial diagram below tables of figures. Rod spoke with effort. “Approved.” Then he went back to the impossibly large object on his view screen. Suddenly he took out his pocket computer and scribbled madly across its face. Words and numbers flowed across the surface, and he nodded.

Of course light pressure could be used for propulsion.

In fact MacArthur

did exactly that, using hydrogen fusion to generate photons and emitting them in an enormous spreading cone of light. A reflecting mirror could use outside light as propulsion and get twice the efficiency. Naturally the mirror should be as large as possible, and as light, and ideally it should reflect all the light that fell on it.

Blaine grinned to himself. He had been nerving himself to attack a space-going planet with his half-repaired battle cruiser! Naturally the computer had pictured an object that size as a globe. In reality it was probably a sheet of silvered fabric thousands of kilometers across, attached by adjustable shrouds to the mass that would be the ship proper.

In fact, with an albedo of one— Blaine sketched rapidly.

The light sail would need about eight million square kilometers of area. If circular, it would be about three thousand klicks across.

It was using light for thrust, so… Blaine called up the intruder’s deceleration, matched it to the total reflected light, divided… so. Sail and payload together massed about 450 thousand kilograms.

That didn’t sound dangerous.

In fact, it didn’t sound like a working spacecraft, not one that could cross thirty-five light years in normal space. The alien pilots would go mad with so little room—unless they were tiny, or liked enclosed spaces, or had spent the past several hundred years living in inflated balloons with filmy, lightweight walls… no. There was too little known and too much room for speculation. Still, there was nothing better to do. He fingered the knot on his nose.

Blaine was about to clear the screens, then thought again and increased the magnification. He stared at the result for a long time, then swore softly.

The intruder was heading straight into the sun.

MacArthur decelerated at nearly three gravities directly into orbit around Brigit; then she descended into the protective Langston Field of the base on the moonlet, a small black dart sinking toward a tremendous black pillow, the two joined by a thread of intense white. Without the Field to absorb the energy of thrust, the main drive would have burned enormous craters into the snowball moon.

The fueling station crew rushed to their tasks. Liquid hydrogen, electrolized from the mushy ice of Brigit and distilled after liquefaction, poured into MacArthur’s tankage complexes. At the same time Sinclair drove his men outside. Crewmen swarmed across the ship to take advantage of low gravity with the ship dirtside. Boatswains screamed at supply masters as Brigit was stripped of spare parts.

“Commander Frenzi requests permission to come aboard, sir,” the watch officer called. Rod grimaced. “Send him up.” He turned back to Sally Fowler, seated demurely in the watch midshipman’s seat.

“But don’t you understand, we’ll be accelerating at high gees all the way to intercept. You know what that feels like now. Besides, it’s a dangerous mission!”

“Pooh. Your orders were to take me to New Scotland,” she huffed. “They said nothing about stranding me on a snowball.”