SLOW CRASH extract by Geoff Nelder

On his way back he tripped as his helmet bleeped into life. An emergency return to ship call! He cursed his clumsiness as he spent nearly five minutes getting upright and back to the airlock. Perspiration bathed his body as he relaxed slightly once back in the command room and saw only one flashing red light. Stretching his neck to read the message on the console as he tried, unsuccessfully, to kick off the tailored space suit, he saw the emergency related to some aspect of navigation. Relax again. He placed the suit in the cleaning unit before settling into his swivel chair before the computer and asked it to tell him the worst.

"Collision in eighty-eight point five three hours."

"What? What's going to hit us way out here?"

"This asteroid will be impacted by another asteroid," the computer had a warm feminine voice but its message was still chilling.

"When is the estimated time of impact? No. You've already said that - eighty-eight hours. How far away is it now?" Singer's brain was racing. He couldn't leave without taking at least enough of this asteroid to set him up for life.

"The intercepting asteroid is a hundred and twelve point seven miles away travelling on a near parallel course but closing at one point two seven miles per hour."

"One mile per hour! You can't call that a collision. How big is it?"

"Two thousand five hundred and twenty seven metres diameter."

In desperation to save his retirement wealth, Singer quizzed the computer about the chances that the incoming asteroid might miss but to no avail. On request. the computer regurgitated its memory buffers with adjustments made by the unique statistics of the situation.

"Collision predicted is of the category known as a Slow Crash. Depending on the geological structure of both asteroids, the impact has an eighty-three percent probability of causing disintegrating fractures of both. The slow speed will not lessen the impact since the masses of the asteroids are so great. Enough to disintegrate the planet."

"Just a minute. Some of your connections must have oxidised. Surely a slow crash is impossible. As soon as any two masses get close enough their combined gravitational pull would accelerate them into a frenzied smash-up. It's just not possible for two asteroid-sized lumps to touch each other gently." He was mischievously delighted to put one over on the computer. The exhilaration didn't last long.

"You are correct for a two particle problem. However..." Singer groaned as the computer gave him a lecture on the complications of multiple particle gravitational fields, the added effects of electro-magnetic fields and even of the influence of the electrical field from a nearby giant gas planet. All in all it added up to the result that it was possible, however improbable, for a collection of debris to be in a dynamic equilibrium as they journeyed together in an orbit around a large body. It was also feasible for a slight perturbation of the fields to edge some of the particles into closer proximity, the acceleration between two being offset by others around them.

Singer felt cheated and morose but after a long think, asked the inevitable question. "Right, let's see. How much time have we to salvage what we can before we have to get away?"

"If the Space-Digger left the asteroid in eight-seven point two hours we should be able to escape any detritus from the collision."

"Right, so we have until then to grab ourselves the juiciest chunks and get them out with the rest of our haul in tow."

There was something that the computer knew would upset Singer but it wasn't programmed to anticipate the pilot's feelings so it held back.

Singer made himself a meal and was leisurely sipping a hot drink while deciding how to make a rapid survey of the asteroid when he suddenly felt an urge to see the incoming asteroid for himself. He ordered up the necessary co-ordinates and punched them into the viewscope. Seconds later a crowded sky filled the large coloured screen. Cross-hairs targeted the ingressor as a pale spot. Nothing seemed to move even though everything moved in more or less the same direction at over 160.000 miles per hour. Everything, except for that splodge that was imperceptibly inching its way closer.

Well, before he blasted off to safety, he was going to salvage what he could. He was going to have to organise a quick mineralogical survey, get any individual samples that might be intrinsically valuable aboard the SpaceDigger and maybe he could blast a sizeable number of pieces off the asteroid and gather them before having to get clear of the area. It needn't be a total write-off: after all, the projected collision might do him a favour by fragmenting the asteroid into more manageable chunks.

He tried to recall what he knew of slow crashes but couldn't. The computer library wasn't much help either. Did it create an explosive impact so the heat of even a slow contact, from friction, fusion gas ignition or radiation, would send projectiles at great speeds in random directions? How far should he stand-off to be a safe observer? Might the two asteroids fuse together and go into a spin like a dumbbell? He set about the survey and during the next twelve hours was able to retrieve some pleasing samples and store them in the hold. Several times while he was floating around on the surface he looked up at the incomer and at his other neighbours. He could never get used to admiring the firmament. Even the silent blackness in between the steady stars drew him. He knew there were several cosmological theories mostly variants of big bang.

He decided he ought to give himself a wide margin of error and put some distance between himself and the coming rendezvous. He sat at the easy-access console and initiated the instructions for take off and escape to a safe distance. Nothing. Singer stared unbelieving at the machine as it politely informed him take off was out of the question.

"But why not?"

"Evidence from back-interpolation indicates it was our presence that caused sufficient perturbation in the localised magnetic and gravity fields to initiate the imminent collision."

"So? Let's get out of here. Make some more perturbations. Oh I get it, there's a directive saying I'm not to disturb planetary motions,' Singer was exasperated.

The sultry feminine voice resumed analysis, 'Since the evidence shows taking off will cause at least three more collisions to occur. I'm programmed to prevent a worsening of the situation."

"But only from the point of view of the asteroids not mine!"

The console stayed silent. It obviously regarded the last statement as rhetorical. Singer tried another approach to change the computer's mind while his stomach told him panic might take over at any minute.

"What could change your decision?"

"A direct order from base is the only way to override any of my computed probability decisions."

"Doesn't the life of your pilot get any consideration in your metal conscience?"

"Only in as far as it does not interfere with the prime directives. It is imperative not to disrupt planetary motions."

Singer thought through this and tried again as if he was cross-examining a witness for the prosecution, "And is the incoming asteroid big enough to be a planet ?"

"It is. That is not all, this asteroid is also within the category size of a small planet."

"Ah! Got you!" Singer raised his voice triumphantly, "Why have you been helping me to take this 'planet' to pieces if you have a directive not to damage it?"

"That is not my programmed directive. Taking parts of any planet does not significantly affect its path of motion but moving about in this unusually dense collection of small planetoids and asteroids is clearly disruptive."

Singer was speechless. He stood up and poured himself a stronger than recommended concentration of liquid stimulant while his mind grappled with the increasingly horrifying situation. He dug out the technical files that were in book form so the computer couldn't tell he was investigating the possibility of taking the ship over on manual. It was another blind. He could turn off the computer but not without disabling the ship stranding him. The system was fail-safed to prevent a pilot from sabotaging or hijacking his own vessel.

The next forty-eight hours were torturous. He went for walks and gazed up time and again to seek some inner peace with himself, to accept his fate, take what was coming as yet another experience and think of a set of words that might unlock the computer.

The threatening asteroid increased in size almost as he stared at it. He stared until his eyes watered. In desperation, he sat heavily on the stool in front of the console and tried everything again for the fifth time. Still no joy.

Out of academic interest he asked the computer if any other asteroids were displaced by their presence.

"Six discernible bodies are moving along routes that are not on the same course they were. Many smaller meteorites are also on impact courses with other bodies besides this one."

Singer thought he could see a way to getting the computer on his side.

"Ah, so even if we sat here until impact, there are already other changes in the equilibrium of the swarm that could create greater havoc than if we took off?"

"That is possible. It would be necessary to compute the trajectories of each body, identify their impact targets, assess the individual probabilities of either disintegration or ricochet deflection and compute the resonance or secondary flight paths that resulted. At each impact the certainty of forecasting the flight paths and hence the stability of the total swarm reduces by thirty-six percent."

"Umm - can you compute the effects of our take-off in the same way?"

"With ease but the probabilities of assessing the secondary impacts remain the same."

"So. the future of the stability of this swarm is virtually indeterminate whether or not we take off!"

"Affirmed." The computer voice synthesiser hardly seemed to pause between its answers in contrast to Singer's agonised synapse-wringing deliberations.

After a long deep breath, Singer launched into what he hoped would be the clincher.