Vengeance 10

The cloud along the western horizon had broken, and reddish light rushed through to flood the distant hills. Below, the city, shrouded in a century of industrial grime, remained grey and dismal. Memling began by describing his chance meeting in 1938 with Wernher von Braun and Franz Bethwig, his subsequent flight from the train, and the encounter with von Braun three days before, which had led to his glimpse of the sealed area.

‘I studied mechanical engineering and was also a member of the British Interplanetary Society,’ he continued, noting that Paul did not smirk or grin at the name as so many others had. ‘Before the war I helped to develop several small rockets that used liquid fuels. I am quite familiar with some of the problems.’

Paul nodded. ‘I think I understand. Tell me about what you saw at the works.’

‘There was sufficient time for me to get a good look. It was a bell-shaped object one and half metres high and half that wide. The bottom flared into a bell muzzle as a rocket nozzle would do. Above the nozzle was a spherical container from which a series of pipes depended. The sphere was most certainly the combustion chamber.’

‘How can you be certain of the size?’

‘The soldiers were moving another one inside. It was on a standard factory cart which stands exactly thirty-six centimetres high on its wheels. I measured one. The rocket motor rose to the level of the soldier’s chin. When he stood upright, he was as tall as I am, which is one point eight metres exactly.’

‘You are very perceptive. Where did you obtain the performance characteristics?’

Memling cleared his throat. ‘An engineer must be a good observer. As for the specifications… I–I calculated them from the dimensions of the engine.’

Paul nodded for him to continue.

‘From the apparent diameter’ — Memling’s voice was feverish with the urgent need to make this man understand — ‘of the nozzle it is possible to estimate the width of the rocket. From the diameter of the combustion chamber it is possible to construct a series of estimates of specific thrust based on the fuels that might be employed. Given that, the rate of fuel and oxidiser use can be estimated, which suggests the amount of fuel that can be carried and thus the possible range. That, in turn, provides an estimate of the weight of explosive that can be carried. Military considerations would further limit the choice of weights; for instance, it would make no sense to shoot a fifty-kilogram payload a thousand kilometres or a six-thousand-kilogram payload ten kilometres.’

Paul was watching the sunset, and Memling wondered if he was really listening. ‘Von Braun told me two years ago that their major problem was to contain the twenty-nine-hundred-degree-centigrade temperatures developed in the combustion chamber. He mentioned at the time they were using liquid oxygen. The only fuels that combine with liquid oxygen to produce that temperature are petrol and alcohol. Knowing the fuel and oxidiser, the combustion temperature, and approximating the rate of propellant/oxidiser feed — which is dictated by the combustion rate — it is possible to calculate speed and range versus payload. The targets are obvious and all within a four-hundred-kilometre range of occupied European territory.

‘For instance, a rocket capable of striking London from this side of the Channel will travel approximately two hundred kilometres from, say, the vicinity of Antwerp. If we assume that the rocket must travel at least three hundred metres per second, and the fuel consumption is thirty kilograms per second, or twice the acceleration of gravity, you can calculate to find that the rocket must produce five hundred and sixty thousand horsepower. With that figure you can refine your assumptions and define such characteristics as fuel load, desirable payload in explosives, and so on. These, of course, provide you with the maximum and minimum dimensions of the rocket.’

Paul had remained silent throughout the discourse, and Memling was afraid that he had overdone it. The Belgian was staring out over the city to the western horizon where the storm clouds had regrouped, forcing the sun to retreat.

‘You are certain of these calculations?’ he asked, and when Memling nodded, he smiled. ‘I was an artillery officer, of the rank of lieutenant colonel. I am an engineer by training.’ He was silent a moment, then stood and motioned Memling to walk with him. They started back along the path, Memling pushing his bicycle and cursing his rumbling stomach.

‘I will do this much,’ Paul said after they had covered half the distance. ‘A message will be sent to London briefly describing your information and conclusions. They may well want a follow-up report.’

Memling clenched his fists on the handlebars and strove to keep his voice normal. He shook his head. ‘That won’t do.’

Paul glanced at him in surprise. ‘Why not, may one ask?’

Memling described the reception his report had received in 1938.

‘Perhaps things have changed… new personnel..’