Voyage (64 page)
Authors: Stephen Baxter
Gregory Dana was at the lectern, fumbling with his thick spectacles, preparing to speak. Udet had not been surprised when Dana had been selected to chair the investigating panel.
On a large screen behind Dana, an image was projected; it showed the Saturn VB stack a few minutes before launch from Pad 39B at Kennedy. The fat MS-IC first stage gleamed white in the sunlight, with its wide tail-fins and the four slim Solid Rocket Boosters clustered around it. It looked like a broken-off piece of some elaborate Moorish temple. The second stage was a squat cylinder atop the MS-IC, bone white, with the silver-gray’ gumdrop shape of an unmanned boilerplate Apollo capsule at the top.
Umbilicals snaked into the stack from the big, complex launch tower, feeding liquid oxygen and propellant into both the liquid stages: hydrogen for the second stage, and RP-1 – kerosene – for the big first stage. Vapor wreathed the upper levels of the booster, dispersing slowly, and Udet could see the sparkle of ice against metal and insulation.
The sky behind the stack was a gray-blue, and heat haze shimmered about the tower.
Udet felt his heart move at the sight. He had never lost his boyish wonder at the sight of such magnificent devices – these heroic machines – wrought by human hands from the raw materials of the Earth, to be hurled toward the planets.
And, of course, that sense of awe was piqued on this occasion by his foreknowledge of the fate of Booster AS-5B04, just a few seconds later.
Udet glanced around. Joe Muldoon, up on the stage with Dana, was moderating the meeting, and much of NASA’s senior management appeared to be in attendance; there were staff from Marshall and Houston and NASA Headquarters, including aides of Tim Josephson, and a heavy representation from the contractors responsible for the system components under scrutiny today.
The presentation was to be a summary of NASA’s preliminary internal report into the problems encountered during the launch of Saturn VB stack AS-5B04, three months earlier. Depending on the
reaction of this audience, and on the NASA hierarchy as a whole to the content of the report, a draft would be finalized and published within the week.
There was an air of tension, anxiety, weariness.
Coming so soon after the Apollo-N tragedy, nobody in the Agency wanted to face up to another disaster, the first loss of a Saturn. Udet had heard the muttering.
Who the hell can we blame for this one?
Dana was speaking, in his thin, frail voice. Udet drew a little more upright in his chair.
‘At six point six seconds before launch, the Saturn’s kerosene-fueled F-1A main engines were ignited in sequence and run up to full thrust, while the entire structure was still bolted to the launch pad. The thrust of the main engines pushed the Saturn assembly upwards, against the restraint exerted by the pin-down bolts anchoring it to the pad. When the Solid Rocket Boosters’ restraining bolts were explosively released the stack’s “stretch” was suddenly relieved …’
On the screen behind Dana, clouds of smoke and steam billowed up around the base of the Saturn stack. Then the four Solid Rocket Boosters ignited, and yellow-white fire plumed from their engine bells. The camera shuddered, as testimony to the acoustic energy spewed out by the stack – but the film was without sound, and the brilliant launch sequence worked through in eerie silence.
The image froze. Billows of smoke stopped their evolutions, and became mounds of gray and white, solid-looking, like dirty ice cream.
Around Udet, rows of lined faces were illuminated by frozen rocket light.
An arrow pointed to a blurred patch of white near the base of the MS-IC; it was just below the ‘A’ of the red stenciled ‘USA’ on the wide hull of the booster.
Dana said, ‘At zero point six eight seven seconds into the flight, photographic data shows a strong puff of vapor spurting from the lower casing of the MS-IC, just above the engine fairing.’ Dana glanced over his shoulder, wrinkling his nose. ‘As you can see here. The two pad cameras that would have recorded the precise location of the puff were inoperative. Computer graphic analysis of film from other cameras indicated the initial vapor came from that level of the MS-IC where the feed from the oxidizer tank exits the propellant tank.’
The MS-IC contained two huge cryogenic tanks. The oxygen tank
was uppermost, and the fuel lower. Fat suction lines carried liquid oxygen through the kerosene tank for combustion in the five huge F-1A engines at the base of the stack. Dana was implying, now, that there had been some kind of problem with that feed.
The film started again, in extreme slow motion; the smoke evolved around the Saturn with glacial slowness. White arrows continued to prod at the offending vapor patches at the base of the MS-IC.
‘Six more distinctive puffs of vapor were recorded between zero point eight three six and two point five zero one seconds. The multiple puffs in this sequence occurred at about four times per second, approximating the frequency of the structural load dynamics and resultant stack flexing …’
The wretched ‘stretch’!
‘You can also see shock diamonds in the F-1A exhaust, another symptom of the stack resonance. At three point three seven five seconds the last vapor was visible below the Solid Rocket Boosters. It became indiscernible as it mixed with rocket plumes and the surrounding atmosphere. Other vapors in this area were determined to be melting ice from the bottom of the MS-IC or steam from the rocket exhaust in the pad’s sound suppression water trays …’
The film began to run at normal speed.
The Saturn tipped away from the launch tower, and rolled, as programmed, onto its back. Udet could see, between the four brilliant stars of the Solid Rocket Booster bells, the pale, almost invisible, smokeless fire of the kerosene-oxygen main engines.
Dana went on, ‘At this point the first indications were received, via telemetry, of a significant reduction in propellant flow to the MS-IC main engines.’
The image froze again. The audience stirred; the sudden cessation of the launch sequence’s hypnotic flow was jarring. An arrow pointed to the five main engine bells.
‘The first visible indication of main engine thrust reduction was detected on image-enhanced film at fifty-eight point seven eight eight seconds into the flight. It is visible in this frame, as a dimming of the plume from the right hand F-1A bell – just here.
‘One film frame later from the same camera, the reduction is visible without image enhancement.’ The engine bell had grown dark, and its four brothers were also clearly ailing. ‘At about the same time telemetry showed a differential between the pressures in the main engine chambers. The right-most booster chamber
pressure was lowest, confirming the growing reduction in the flow of propellant.
‘At sixty-two seconds into the flight, the control system was responding to counter the forces caused by the differential thrusts from the main engines …’
The film ran on, slowly; the main engines flickered or died, but the Solid Rocket Boosters still blazed with fire. The stresses on the stack were enormous, as the SRBs tried to compensate for the loss of the main engines.
No change in the attitude of the complete stack was visible to the naked eye. Udet knew, however, that at this point his doomed Saturn was already fighting for its life.
Dana cleared his throat, and pushed his glasses against his face; his gestures were small, precise, almost apologetic. ‘Analysis has shown that the primary cause of the malfunction evident at this point in the flight was the feeder-valves set in the underside of the MS-IC’s oxygen tank, which carry oxidizer into the feeders to the main engines. Tests have indicated that under certain circumstances, the valve design could go into a “flutter” regime and effectively shut off the supply of oxidizer, resulting in a total failure of all F-1A engines. As was observed here. The frequency of the possible flutter has been shown to be close to the frequency of the launch “stretch” and to oscillations caused by instabilities in the burning of the Solid Rocket Boosters …’
Udet massaged the bridge of his nose, trying to control the irritation that flared within him.
We know this. My team at Marshall, and the contractors independently, determined this root cause of the fault within an hour of the malfunction
. The Saturn had already been vibrating, from the ‘stretch,’ at three or four cycles a second just after launch. Then one of the Solid Rocket Boosters had started vibrating lengthwise, at about the same frequency. Such oscillations had been observed before. But the coincidence of frequency was unfortunate, for that frequency, as it turned out, had been just right to set up standing waves in the valve system carrying liquid oxygen into the main engines …
We know all this, and we are already working to correct the problem. Have you no more wisdom to add than this, Doctor Dana?
But now Dana was continuing; he was describing how some preliminary tests, carried out during the MS-IC’s design stage, had indicated the possibility of a resonant flutter – although no change in the stage’s design had resulted – and he even referred to the
problems encountered with the Apollo-N flight, when similar resonance problems had caused that stack to pogo.
That link with the fatal Apollo-N mishap showed Udet clearly which way the report was shaping.
It was ludicrous, of course; anyone who understood anything of the complexity of a ship like a Saturn – with its millions of moving parts – would recognize the impossibility of adjusting the design to counter
every
possible problem that could be conjured up. There was never the time, or the resources; the realistic way was to balance the risks, and exercise judgment as to what is acceptable, and what must be changed. Why, if one waited for the perfect rocket, one would never fly at all!
Udet felt enormously tired. He was sixty-eight years old now. And sometimes – especially since the death of von Braun – he wondered whether the battle was still worth the effort, whether he still had the strength for the endless struggle to convince the Americans to accept the great rockets he was building for them.
Udet had donned something of the mantle of von Braun, since Wernher’s retirement a decade earlier. He had even inherited Wernher’s office, here on the tenth floor of Marshall’s headquarters building. But Udet had no pretensions; he knew that he was no substitute for Wernher. The Americans had adored von Braun: they responded to him, Udet thought ungraciously, as they did to evangelists, and the salesmen of cars. And, it seemed, questions about the Germans’ past – possible complicity in ‘war crimes’ during the Peenemunde period – were irrelevant for Wernher.
Well, Wernher was dead now. And it was different for Udet. He knew that, try as he might, he could not help but project an aloofness, an aura of the disdainful Prussian aristocrat. The Americans did not trust Udet; and they appeared to find it much easier to believe ill of him than ever they had of von Braun.
And meanwhile, he had been forced to watch as Gregory Dana had risen in status and power within the organization. Being the father of the lost hero James, and the fact that his once-vilified mission mode had been chosen as the basis for the new Mars program, had raised Dana’s status almost to national celebrity.
And now, Dana continued to pronounce his damning testimony on Udet’s life work, his tone dry, level, like a soulless prosecutor.
Udet’s dark, dwarfish twin.
‘Beginning at about seventy-eight seconds, a series of events occurred extremely rapidly that terminated the flight. Telemetered
data indicate a wide variety of flight system actions that support the visual evidence of the photos, as the Saturn struggled against the forces that were destroying it.
‘At seventy-eight point nine seconds the lower strut linking Solid Rocket Booster Number Four and the MS-IC was severed or pulled away. This failure was evidently caused by the abnormal stresses placed on the structure by the failure of the main engines. SRB Four rotated around its upper attachment strut. This rotation is indicated by divergent yaw and pitch rates between the Solid Rocket Boosters.
‘At seventy-nine point one four seconds a circumferential white vapor pattern was observed blooming from the side of the MS-IC. This was the beginning of the structural failure of the MS-IC’s propellant tank, which culminated in the separation of the aft dome of the tank. This released massive amounts of RP-1 from the tank and created a sudden forward thrust of about two point eight million pounds, pushing the propellant tank upwards through the motor casing toward the S-II. At about the same time the rotating SRB Four impacted the lower part of the MS-IC’s liquid oxygen tank. This structure failed at seventy-eight point one three seven seconds, as evidenced by the white vapors appearing in this area …’
The images on the screen continued to unroll, frame by frame, their pace matching Dana’s dry, analytical delivery. The pictures were blurred and shrouded by the haze of distance, and a fog of escaping vapor, but it was just possible to see how the Solid Rocket Booster was swiveling around, and its conical tip was puncturing the flank of the central first stage.
Then brilliance erupted, within the space of one frame, engulfing the image.
‘Within milliseconds there was a massive, almost explosive, burning of the propellant streaming from the bottom of the failed tank. At this point in its trajectory, while traveling at Mach one point nine two at an altitude of forty-six thousand feet, the Saturn was totally enveloped in the explosive burn. The Apollo spacecraft’s reaction control system also ruptured, and a hypergolic burn of its propellants occurred; the reddish-brown colors of this burn are visible on the edge of the main fireball. As you see here. The second stage also ruptured at this point, adding one million pounds of propellant and oxidizer to the fireball. The stack, under severe dynamic loads, had by now disintegrated into several large sections which emerged from the fireball; separate sections which can be identified from film include the instrumentation module, trailing a
mass of umbilical lines, and the first stage’s main engine section with the engines still trailing vapor …’