by Jeff Pollard
Over the Indian Ocean, the final deorbit burn was performed. Lasting less than a minute, the burn pushed the astronauts into their seats at just a quarter G. But to the people who had been in weightlessness for two weeks, it felt much stronger than that.
With the deorbit burn performed, the Griffin Trunk, along with the solar panels, was discarded, blown off by explosive bolts and exposing the Griffin's heat shield for the first time all mission. Tim then gave the Griffin another push with a short burst from thrusters, making sure that the Griffin and the Trunk would be far apart when they both intersected the atmosphere in about 20 minutes. The Trunk would be totally consumed by fire, and any small parts remaining would harmlessly fall into the Pacific Ocean.
The first noticeable sign of re-entry is visual. Trails of ionized gas are a blur outside the windows well before the astronauts would feel the capsule slowing down. Soon their deceleration would be difficult to ignore. The PICA-EX heat shield performed marvelously and the crew were subjected to a comfortable re-entry with a peak of only six Gs. As per their training, the astronauts take shallow breaths, keeping their lungs almost full the whole time. A deep breath would be very difficult to take as you would have to overcome the sextupled weight of your chest. Having grown accustomed to the weightlessness of orbit, the six Gs seemed even stronger, but the personally tailored foam-lined seats helped.
Kingsley was already imagining their welcome on the SpacEx cutter. A documentary crew was there waiting to film the recovery of the capsule from the sea as well as their first steps back on the surface. The mission was being covered world-wide like no recent space mission.
As the capsule dropped through 30,000 feet it had slowed to less than 400 mph. If unimpeded, the Griffin would slow all the way to about 140 mph, its terminal velocity. Friction with the atmosphere took away more than 17,000 mph, the parachutes would only be asked to cover that last 120 mph to allow a nice soft splashdown instead of a deadly impact. Having slowed to sub-sonic, the Griffin had left the danger of burning up like a meteor. The last major danger was more in the realm of a head-on collision at highway speeds. Then again, it doesn't matter if you bleed off 17,000 mph only to fail to get rid of that last 100 mph, dead is dead.
“Coming through 30,000 feet,” Kingsley reads off the telemetry. “Here come the drogues.”
But the drogue chutes didn't come. “Negative on the drogues,” Commander Bowe says.
“Doesn't look like the computer gave the order,” Kingsley says.
“Overriding,” Commander Bowe says, hitting the button to release the drogues, something the computer had failed to order for some unknown reason.
Normally the three drogues were automatically released by the flight computer at 30,000 feet and each would stabilize the Griffin and eventually yank out the main chutes at a safer speed, when the mains wouldn't be torn to shreds.
As the drogues deployed, one drogue failed to open immediately, instead it became tangled around the other two drogues. It wasn't a serious problem as the drogues only helped the mains come out. The mains could be deployed manually by a motor that would physically push them up out of their recessed positions. However, when deployed in this manner, they would be less likely to open correctly. So when there were only two good drogues, there really was no cause for alarm. That was until an error hidden deep in the Griffin's programming reared its ugly head.
The Griffin's thrusters that rolled the capsule to keep control during re-entry were supposed to be shut-off at around 100,000 feet as they were no longer necessary and they could interfere with the parachutes. Unbeknownst to the crew, the flight computer had accidentally been set into a passive mode during re-entry. Some aspects of the flight computer worked much like cruise control in a car. It would automate a task (like maintaining speed) until there was an input from the pilot, at which point it would give up control. You don't want to have to turn off cruise control to stop your car, instead, when you hit the brakes it automatically turns off the cruise control. While coming in during re-entry, Commander Tim Bowe took control to manually roll the capsule to add lift and send it farther downrange. This was because the flight computer was set to deliver the Griffin to set GPS coordinates at a point in the sea, however the SpacEx cutter wasn't at that point, but about fifty miles west of that point because of rough seas.
So when Commander Bowe rolled the capsule and sent the Griffin a bit farther downrange, the flight computer flipped into a passive mode so that it wouldn't automatically turn things on and off or deploy parachutes at an inopportune time.
After Commander Bowe performed the roll, he turned the flight computer back to active-control, however the error hidden in the Griffin's flight computer showed up here. Since the flight computer still saw the initial destination fifty miles west of the new destination, it realized that it was impossible to reach the original target with just passive controls. Only by burning the landing engines could the Griffin change its trajectory enough to hit that target. Since the flight computer knew it would require a major maneuver, it refused to turn on. It should have then notified both Commander Bowe and Kingsley that it saw its instructions as impossible. They could have then quickly changed the target destination to the new target and the flight computer would have been perfectly capable of landing the capsule from there.
However, the flight computer didn't tell anyone that it saw its instructions as impossible and so it refused to turn on. But the real problem came when Bowe flipped the flight computer back to active and the display said that it was active. When given impossible instructions, the display should have shown the flight computer was still passive, but a mistake in the programming led to both Kingsley and Commander Bowe seeing the flight computer in control. Had either of them been very focused, they would have seen that the flight computer's target destination had not been updated and that something was up. But instead, they concentrated more on the telemetry, the parachutes, the altitude.
So when the capsule hit 30,000 feet, the flight computer was not active and thus was not going to order the drogues to deploy. So Commander Bowe gave that order and the drogues came out. One drogue became twisted and initiated a roll. Had the flight computer been active, it would have already shut down the roll-control thrusters that try to maintain the present roll-state of the capsule. But it wasn't, and so when the capsule started to roll because of the twisted drogue, the roll-control thrusters fired up to stop that rolling motion. The thrusters worked so quickly that the passengers didn't even notice the capsule was rolling at all. The highly toxic nitrogen tetroxide and unsymmetrical dimethylhydrazine propellants for the control thrusters were now burning just feet away from delicate parachutes.
Caroline is the first to realize the roll-control thrusters are on, though she doesn't really understand the problem. She hears the pulsing of the thrusters and is the first to mention it. Kingsley and Bowe were perhaps a bit too preoccupied with the parachutes to notice the relatively quiet sound of the control thrusters against the much louder sound of the wind.
After she mentions the noise, Kingsley looks to another panel and sees that the roll-control thrusters are indeed firing.
“Why are those firing?” Kingsley asks Bowe.
“They shouldn't be,” Bowe replies quickly. Kingsley manually turns them off and the capsule then begins to roll. The roll causes the two good drogues to start to get tangled with each other. “They're tangling!”
“Go ahead and deploy the mains manually,” K says to Bowe.
“Roger,” Bowe says. He presses the button and just feet above them a motor pushes the parachutes out of their recessed position and they start to open. Without the help of any good drogues, it would take a little longer for the mains to properly open. Kingsley and Bowe closely watch the feed from the docking camera that shows the chutes above them. One of the mains shreds immediately. A second main seems to open properly only to then tear away from where the lines connect to the capsule.
“Shit, their covered in hydrazine,
” Kingsley says ominously. The spent fuel from the roll-control thrusters had bathed the chutes in corrosive liquid that was now eating through the chutes and the lines.
“Alright, looks like we have just one good chute,” Bowe says. “How hard will we hit the water?”
“We can't trust that it will hold,” Kingsley says. “But 40 mph if we're lucky.”
“Alright, let's get the landing thrusters online.” Bowe says.
Theoretically, they could turn on the landing thrusters and slow the capsule to a soft splashdown. Theoretically. That's all the certainty they have because no capsule returning from space had ever made a powered landing. No Griffin had even attempted it, though they had planned to try it with several Cargo Griffins, they had yet to try it. Activating the rockets while they faced a headwind of over 150 mph was not necessarily a slam dunk, even if the fuels were hypergolic. To further complicate matters, the roll-control thrusters worked on the same fuel that the main landing engines used, and since those roll-control thrusters had fired continuously for some time before being noticed, the fuel in the tanks was a little low. That meant they would have to activate the landing engines a little later than they otherwise would.
“Watch the fuel gauge,” K says.
“I see it,” Bowe says. “I want to fire them up now, make sure they work.”
“K,” Kingsley says. Bowe pushes the throttle up and hits the button to activate the landing engines. Nothing happens. They fall through 25,000 feet with one good parachute and no landing engines.
“Negative ignition,” K says, seriously alarmed now. “Alright, everybody out of your seats and get your parachutes on. We might have to ditch.”
The parachutes, large enough to fit over their flight suits, were stored in a panel underneath Arnold's seat. Parachuting wasn't a very good proposition while wearing a flight suit. In his head, Kingsley gives them each about a 25% chance of drowning. Ordering everyone to parachute was likely a death sentence for one of them. Staying in this capsule under one good chute was a death sentence for everyone. While the passengers unbelted and panicked while trying to extract the chutes, Kingsley tried to figure out why the landing engines weren't turning on.
“That means you too,” Kingsley says to Bowe. Bowe isn't going to abandon his post yet and simply looks back to K defiantly.
“Why won't this thing light,” Bowe says, hitting the activate button again.
It wouldn't light because the computer wasn't listening to any inputs for the landing engines. It wasn't listening because the bug in the software that prevented the flight computer from attempting a drastic maneuver to change its trajectory had frozen the landing engine input at zero. The freezing of the input was supposed to only effect the flight computer and not the pilot's controls, which should have automatically overridden whatever the flight computer was doing. But the same bug that showed the flight computer as active when it was passive had confused not just the crew, but also other parts of the flight computer, which now saw the order to activate the landing engines as coming from the flight computer and not from the pilot.
Kingsley and Bowe didn't know this, nor did anyone at Mission Control as the two groups tried to figure out a solution before they either hit the sea or ordered everyone to try their luck under a personal parachute. They ran diagnostics, they flipped settings and tried again, but none of these measures would overcome the bug in the flight computer.
Kingsley cursed the computer as he realized that the capsule might very well kill five people because of some error in programming preventing him from turning on perfectly good engines. The three passengers were still struggling to get their chutes strapped on, something they could do in less than a minute in a calm situation.
“Maybe we should get our parachutes on,” Bowe says, looking to Kingsley as they passed through 15,000 feet. Bowe starts undoing his straps. Caroline kneels in her seat next to Kingsley, parachute in hand, looking to him, her eyes begging him to get out of his seat and both help her with her chute and to put on his own.
“Hawthorne, what are my exact coordinates?” Kingsley says with a calm pilot voice. He would never break rule number one of being a pilot. Mission Control comes back and told Kingsley his precise GPS location.
“Recovery, Griffin, how rough are the seas?” Kingsley asks. Caroline stares at him, jaw agape, wondering what in the world he is doing. Obviously he isn't thinking clearly.
“Fifteen foot seas,” the call came back from the cutter.
“Hold on,” K says to his passengers who are all out of their seats. He presses the button to cut all the chutes and the Griffin starts falling a bit faster as the capsule leaves the chutes behind.
“What are you doing!?” Bowe shouts as he slips from the sudden acceleration while trying to put on his chute. Kingsley's stomach rises up in his chest as they drop, but he ignores this feeling and enters the exact coordinates of the Griffin into the flight computer, changing the altitude from their present position to an altitude of 15 feet, and doing some math in his head to put the destination a little bit east of where they currently are.
Then Kingsley flips the flight computer back to active. Having updated the destination, the flight computer saw that it was right on target, with a trajectory taking it almost exactly to its goal. With the parachutes already having been cut, the flight computer automatically entered an abort mode in which it would perform a powered landing. The sub-routine that watched to make sure the computer wasn't doing anything drastic like trying to abruptly change course, the very sub-routine that had the bug, saw that the flight computer was working within its parameters, and thus it unlocked the restrictions on the flight computer. The flight computer saw the low fuel and shifted into an alternate landing profile where it would wait until an altitude of 2000 feet to activate the landing engines. The more abrupt the landing burn was, the less fuel it would require. This is because the longer burn has more “gravity loss,” which is usable thrust that is lost to fighting gravity. Hovering is all gravity loss, so a longer burn, while not a hover, has more gravity loss. The opposite of a hover, a suicide burn, has almost no gravity losses.
Kingsley could have then powered up the landing engines and found out whether his quick-thinking had done the trick and piloted them in for a safe splashdown, but he didn't want to try to override the flight computer right now, since the bug that got them in this mess was in the area of flight computer-pilot-interaction and overrides. He didn't want to risk running back into the bug which he didn't yet fully understand. So that meant they couldn't know if his gambit worked until they hit 2000 feet and the flight computer ordered the landing engines to fire up. They were at 10,000 feet and falling at 300 mph as Kingsley undid his straps and sat upright, putting on his parachute that he hoped he wouldn't need to use.
“Blow it?” Bowe said, standing up and reaching for the hatch.
“Not yet!” Kingsley replied. Kingsley whips his chute on in a flash and gets back in his seat.
“Everybody get in your seat!” K orders.
“What!?” Branson shouts.
“K! They won't fire!” Bowe shouts.
“Now!” K orders. Everyone gets in their seats, following K's lead, but not understanding why. The Griffin falls through 5000 feet, falling at about 200 mph. If the engines didn't kick in at 2000 feet, they would have less than 12 seconds before they hit the water. When they hit 2000 feet, either the engines kick in and they are hit with about 1.5 G from the engines slowing them, or they'll continue in free-fall and have only about 10 seconds before the capsule hits the water. That's 10 seconds to blow the hatch and get 5 people out the door.
K eyes the altimeter as it rushes toward zero. 2200. 2100. 2050. 2010.
“Now!” K shouts, banging his hand on a panel. Just then the landing engines turn on and push everyone down in their seats. The engines' rumble can easily be heard in the capsule and the sound of the wind rushing by disappears.
“What did you do?” Bowe asks, amazed.
“Percussive maintenance,” K replies simply.
The capsule slows through 85 mph at 1000 feet. At 500 feet they're going only 65 mph. The capsule comes to a near stop, dropping at only 5 mph as it reaches the target altitude of 15 feet. The sea has 10 foot swells and the Griffin happens to come down in the trough of a wave. At its near hover, it doesn't so much splashdown as it is splashed upward by a wave. The engines shut down and the cabin of the Griffin is practically silent as it begins to bob in the seas.
To the three passengers, the end of the flight is like a sensory deprivation tank. Arnold and Richard look out the windows of the capsule to make sure that they have indeed safely landed in the ocean.
It was in fact, the softest landing back on Earth in the history of manned space-travel. Not even the shuttle, landing on a runway, could top the smoothness of this splashdown.
“Hawthorne, Griffin 7, we are at stable one,” Kingsley says as calmly as he can. Tim punches him on the shoulder with glee.
The rest of the world witnessed their splashdown as the SpacEx cutter was a mere four hundred yards away. The documentary crew captured the capsule coming down in a blaze of glory, perched atop eight long flames.
The cutter then pulls alongside the Griffin within five minutes of splashdown. A crane extends from the ship and two trained divers walk across the crane and jump on top of the bobbing capsule to attach the crane's cables to the top of the capsule. The crane raises the capsule out of the water and sets it down on deck. The numerous cameras crowd around as the inward-opening hatch disappears into the cabin. The first one out of the capsule and into the limelight is Sir Richard Branson.
Branson hogs the attention while talking about being the first paying customer to Earth orbit on a private spaceship. The passengers are out first, then Commander Bowe insists on Kingsley going out before him. As Kingsley exits, the attention turns to him, the modern day Howard Hughes, but he dismisses the attention quickly and heads into the ship to find Caroline who has made a bee-line to the bathroom.