by Mark Anson
No, she was alone, and all she had was Wesley’s words to sustain her.
Tracey looked steadily at her. ‘Very well. We will begin by presenting the case against you, and you will then have the opportunity to speak in your defence. I understand that you will not be calling any witnesses?’
‘No sir.’
Tracey nodded, and she could see him assessing in his mind how long this was going to take. ‘In that case, may I ask Colonel Jordan to open the case against you.’
A shock ran through Clare’s body. Jordan was the head of the Advanced Tactical Training School – much of USAC’s interception doctrine and procedures had been written by him. If they had intended to go easy on her, this wasn’t the way.
Jordan glanced at some papers in front of him, and looked levelly at Clare, sat there alone in front of the panel.
‘Captain Foster, on July seventeenth of 2148, you were in command of the USAC interceptor Mesa, conducting an attack bombing run on asteroid 2010 TG4. Following a partially-successful de-rotation charge on the asteroid, you took the Mesa towards the target, which was still rotating at a dangerous speed. Despite clear orders to the contrary, you ignored the warnings of the Executive Officer, Lieutenant Collins, and you continued the approach to less than minimum safe distance …’
It didn’t go as she’d hoped.
She realised, within a few minutes of Jordan starting to speak, that they had abandoned her. Every aspect of her performance that day, even down to her conversation with Randall beforehand, when he had offered to let Collins do the run for her, was presented in the most negative terms they could muster.
The death of her father, far from being a possible explanation for her behaviour, became an example of her lack of judgement. She should have listened to Randall, and handed over command of the Mesa to Collins when she could, and assisted him in hitting the target. Nobody would have blamed her. Instead, she stubbornly refused to acknowledge that her judgement might be flawed, that—
It went on. They played the cockpit voice recorder tapes, listening to the sound of the flight computer’s strident warnings, of Collins telling her:
‘I’m your XO. This is too close for safety.’
Jordan presented a detailed trajectory analysis, showing that the close approach could have been avoided, and the charge placed successfully. The coloured velocity and acceleration vectors on the screen blurred in Clare’s eyes, as she realised she was being hung out to dry.
‘I’m your XO. This is too close for safety.’ The words repeated in her mind as she listened, and responded to their questions, but there was little she could say that they hadn’t already anticipated.
There was no mention of her recent mission, no recognition, no saving of her career.
She was outside again, waiting to go in. She felt numb with shock; her reputation and performance had been taken apart, piece by piece in front of her. Too late, she realised that she should have brought someone as a character witness, anything, to mitigate the stream of criticism that was directed at her.
When it was her turn to speak, she had faltered over her opening words. She explained how much she wanted to make a successful deflection, how she took a risk, and that the deflection had been a success. She had spoken of the shock of seeing the Las Vegas take a direct hit, of having to reorganise the attack. And lastly, and it was right at the end, she mentioned her father. She knew by then that none of it was any use, but she said it anyway.
The cross-examination of her testimony had been particularly harsh. The officer introduced as Colonel Helligan had been brutal, tossing aside her grief and her shock, and focusing on her lack of judgement in not handing over command to Collins. At the end, she was barely able to keep herself from hanging her head in shame, but she kept her chin up, staring resolutely at a spot on the wall just behind the panel.
They would be talking amongst themselves now, she thought, rearranging their papers, nodding to each other. We seem to be all agreed. We can’t have captains flouting standing orders. And allowing a civilian to gain control of a ship she was responsible for. A sad end to a promising career. Where could she be posted next? Somewhere where her talents could be out to use, but where she would be less likely to make such an error of judgement again. A training role, perhaps? Colonel Helligan had some openings on Guam.
Would the Colonel take her under his wing, try to salvage something of this sad affair? The Colonel frowned. It might be difficult for her to accept such a role, but he would try. A lot would depend on her, and her attitude.
Heads nodded. The Colonel would try. A lot would depend on her. It was as it should be. Were they all ready to ask Captain Foster back in?
When she went back in, she would see her sword on the table in front of her. In an age-old tradition, if the hilts faced her, she would be innocent of the charges. If it was pointed towards her, then she would know the bad news before it was delivered.
The door to the courtroom opened.
‘Ma’am, they’re ready for you now.’
Clare Foster, captain in the United States Astronautics Corps, stood up and carefully straightened her uniform. She lifted her chin, and keeping her head high, she waited as the door was held aside for her, and went into the room where her sword lay.
Background Material
BACKGROUND NOTES
The asteroids
Most people have heard of asteroids, especially the giant impact about 65 million years ago that brought about the mass extinction event at the end of the Cretaceous Period, ending the age of the dinosaurs. But what exactly are asteroids, and where do they come from?
A mere fifty years ago, a textbook on the solar system would have shown nine planets (Pluto, at that time, was considered one of the planets, an accolade it no longer holds) with Neptune and Pluto taking turns with the honour of being the outermost body. The book would also have shown a ‘ring’ of small objects between the orbits of Mars and Jupiter, the largest of the gas giants. These are the main belt asteroids; a collection of assorted small bodies that fill a ‘missing gap’ where a planet could have existed.
The Solar System is now understood to be a much larger and more complex system than this simple model suggested. Early attempts to explain the asteroids suggested that they were the debris of a larger planet, shattered in some primordial collision. Modern observations, however, show that this perception is misleading, and the main belt asteroids are just one group of a vast number of small bodies that orbit the Sun at varying distances and locations. Recent work on the dynamics of the early Solar System suggests that most the asteroids may never have been part of any planet at all, and are planetesimals that never quite made it to form a planet. Gravitational interactions with the early Jupiter perturbed them into tilted, eccentric orbits that resulted in them smashing into one another at high velocities, preventing them from accreting into a larger body. Further interactions with Mars and Jupiter gradually shepherded this rubble into the main belt, and two other areas located 60° ahead and behind Jupiter in its orbit (the Trojan asteroids, occupying the Lagrangian L3 and L4 libration points).
The total mass of the asteroids in these regions combined is thought to be about 3.0 x 1021 kg, or roughly 4% of the mass of the Moon. They vary from the biggest, Ceres, at 975 kilometres diameter, to objects less than a hundred metres across. The four largest asteroids – Ceres, Pallas, Hygiea and Vesta – account for over fifty percent of the total mass, with the number of asteroids at smaller sizes increasing in a roughly logarithmic distribution, until there are literally tens of millions of asteroids below one kilometre in size.
Asteroids are divided by their composition into three main groups: the chondrites, the stony asteroids, and the metallic asteroids. The most common type is the chondrites, which account for over seventy percent of known asteroids. Chondrites are very dark, almost black, and their composition reflects the carbon-rich makeup of the primordial solar disk. Some of them are thought to be the extinct cores of ancient come
ts.
Asteroids are further divided into families by their orbital characteristics, and association with other objects – for instance the Earth-crossing asteroids.
It is important to appreciate that the asteroid main belt, while having a comparatively large concentration of small objects, is almost entirely empty space, and most asteroids above a certain size are millions of kilometres from any neighbour.
Further out in the Solar System, beyond the distant orbit of Neptune, there is a further, even larger realm of asteroids and other objects, called the Kuiper Belt. The Pluto-Charon system is perhaps the best-known member, and is now classified as a dwarf planet.
Some of the objects in the Kuiper belt are neither asteroids nor dwarf planets, but are comets. Comets are small, irregular-shaped bodies composed mainly of ice, dirt, frozen gases and other volatiles. Occasionally, they are perturbed from their orbits and fall in towards the Sun and inner planets. As they draw closer to the Sun they heat up and lose some of their volatile components in great tails, often millions of kilometres in length. It is these immense tails that give comets their spectacular comas in the night sky.
Comets also move incredibly fast, which is why they often only last a few days in the night sky. As they fall inwards from their distant orbits towards the Sun, they trade their potential energy for kinetic energy. Were a comet to strike Earth, it would cause considerably more devastation than a slower-moving asteroid of the same size, due to the comet’s greater kinetic energy.
The chances of a collision
The Inner Solar System has been bombarded by objects from space – comets, asteroids and planetesimals – since primordial time. The surfaces of Mercury and the Moon, which are less altered by tectonic processes than Earth, Mars or Venus, show this graphically. Most of the impacts date from the late heavy bombardment – a time when the planet Neptune was moving outward into the Kuiper belt, sending great showers of objects inwards. The impact rate then fell off, as the Solar System settled down into a dynamically more stable situation.
About ten thousand tonnes of material falls to Earth every day; one only needs to lie in a field one summer’s night and watch the night sky to see several shooting stars or meteors. Most of these are the size of grains of sand, but larger objects are commonplace. Many burn up in the atmosphere, but some are large enough to make it to the ground as meteorites.
Occasionally, much larger objects survive to Earth’s surface and cause devastation. The Tunguska impact is an example of a body thought to be about a hundred metres across that exploded over Siberia in 1908, levelling an area of about two thousand square kilometres. The Chelyabinsk event of 2013 was caused by an object about twenty metres in diameter that also exploded above ground.
Even more impacts are suspected to occur, but go unreported because they take place over water, or remote locations.
There is very little chance of detecting a chondritic body less than a hundred metres across until it impacts; they are very dark and move very fast, and there would be no warning of its impact. Larger bodies reflect more sunlight and can be seen in surveys, but there is still a class of bodies known as lost asteroids whose orbits were not computed with enough accuracy before they disappeared from view.
Thanks to considerable efforts by several organisations working together under the Spaceguard programme (itself a reference to Arthur C. Clarke’s classic sci-fi novel Rendezvous with Rama) there are now believed to be no objects with a diameter greater than one hundred metres that have any chance of collision with Earth in the next few hundred years.
2010 TG4
2010 TG4 is of course a fictitious object, loosely based on the real asteroid 2004 TG10, which is monitored and classified as a Potentially Hazardous Asteroid (PHA) by the Minor Planet Center. Its orbital period, eccentricity and inclination suggest that it is indeed related to the much-larger Comet Encke, discovered in 1786 by Pierre Mechain. Its orbit takes it out beyond Mars, and back in again to within the orbit of Mercury, before retreating again.
2004 TG10, and the other planet-crossing asteroids that lie close to the ecliptic plane, are dangerous over geologic time in that their orbits are unstable; gravitational effects caused by interactions with the inner planets will eventually cause them to plunge into the Sun, hit one of the planets, or be ejected from the inner Solar System altogether. Their orbits can also be altered by a collision with another body, and this scenario is described in the story.
The chance of an orbit perturbation like this causing any object (or fragments of it) to head directly towards Earth is vanishingly small. What might be more likely is that the perturbed orbit would evolve over many centuries, making many close passes to Earth before finally impacting. For dramatic purposes, this process has been shortened in the story.
Asteroids that were originally part of another larger parent body are not unusual. At one point, the asteroid that ended the age of the dinosaurs was also believed to be a fragment of Comet Encke, but this theory is now thought to be incorrect.
Asteroids have an enormous destructive potential because of their speed – the impact energy is proportional to the square of the object’s velocity, making even large boulders extraordinarily dangerous. Objects above a few hundred metres deliver enough energy to cause widespread regional devastation, and anything much above about three kilometres would potentially end human life on the planet. Yet despite delivering destruction on a global scale, asteroids and comets are also thought to have brought life to the early Earth, by delivering quadrillions of tonnes of water, and helping to form the oceans that we see today, where life on Earth evolved.
Psyche
The large asteroid Psyche (or 16 Psyche, to use its formal astronomical name) is a real object, discovered in 1852 by Annibale de Gasparis, in the main asteroid belt between the orbits of Mars and Jupiter. It is extremely dense for its size (240 km), and contains about 0.8% of the total mass of the asteroid belt. Radar observations suggest that Psyche is almost entirely nickel-iron, which explains its very high density, and it is thought that Psyche could be the exposed core of a much larger parent body, shattered in an ancient impact. Other asteroids are far less dense by comparison.
Psyche is the largest M-type (metallic) asteroid discovered, making it unique amongst the asteroids. Psyche’s unique nature, and the possibility of mining such a rich concentration of metal, makes it a promising target to explore. A Psyche orbiter mission was selected as a NASA Discovery mission in January, 2017, for a planned launch date in 2023.
Deflection strategies
Large objects – more than a few kilometres in diameter – are extremely difficult to deflect if they are on a collision course with a populated world, unless you are lucky enough to get several years’ notice. Fortunately, such objects are extremely rare, having been shuffled into relatively stable orbits billions of years ago. The real hazard comes from much smaller objects, which are worryingly common. The minimum size of a ‘catastrophic’ object is coming down with every passing decade, as our population rises and cities grow ever larger and more vulnerable to damage. Had the object that caused the Tunguska impact hit Manhattan Island, or central Italy, or Hong Kong, instead of a remote and sparsely-inhabited wilderness, then the perception of threats from space would today be very different.
Simply attempting to ‘destroy’ an incoming asteroid by bombarding it with nuclear explosions, Hollywood-style, is unlikely to be successful. Even if the object could be broken up, the effect would be to create a shotgun-like swarm of smaller objects, each capable of regional devastation. Indeed, many asteroids are thought to resemble ‘rubble piles’ held loosely together by gravitational or frictional forces, and any attempt at destroying them would result in them shattering.
A more promising method is to alter the velocity of an incoming object by a tiny amount, which if applied sufficiently far in advance would result in the object missing Earth completely. The key parameter is warning time.
Deflection techniques include u
sing space vehicles to push against small objects, using a laser to vaporise the surface and create a small rocket effect, or carefully-placed nuclear explosions just above the surface to impart an impulse to the body without shattering it. The most appropriate method will depend on the circumstances, and the asteroid’s physical characteristics. Most asteroids rotate, so some of these techniques need careful timing to succeed, and this scenario is described in the story.
The Mesa
The deep space interceptors described in the story are stripped-down versions of the passenger-carrying space tugs described in Acid Sky and Below Mercury. The primary requirement of an interceptor is for a large ∆V (delta-vee) capability, to match position and velocity with target objects, and then to achieve deflection with the most appropriate method.
The Mesa is one of the Philadelphia-class interceptors, based on the San Diego-class deep space tugs. This second-generation interceptor features a stronger and more compact design, and a gas core nuclear engine that utilises a nuclear reaction taking place in an incandescent, fissile gas (uranium tetrafluoride) to vaporise and expand the liquid propellant, providing high levels of thrust. The engine uses a closed-cycle system, keeping the fissioning gas inside a transparent container, and heating the fuel through intense thermal radiation.
Alternative propulsion systems for deep space include various kinds of electric and electromagnetic thrusters. Although these are remarkably efficient compared to nuclear thermal engines, they do not offer the very high thrust levels that are necessary for asteroid interception, deflection, and tolerable journey times in a manned spaceflight context.