Riding Rockets

CHAPTER 35 Riding a Meteor

“Fifty seconds.” Hoot gave the time remaining until the OMS deorbit burn. I floated behind Jerry Ross and watched the countdown on the computer displays. As the burn execute time neared, I tightened my grip on Jerry’s seat. The one-quarter G of the thrusting OMS engines was trivial but it was enough to put anything unrestrained on the back wall, me included.

Astronauts have great faith in the OMS engines. They are the essence of simplicity. They have no spinning turbo-pumps to worry us, not even an igniter to fail and jeopardize our lives. The fuel and oxidizer are pushed into the combustion chamber by helium pressure, and their chemical composition causes them to ignite on contact. No spark needed. Getting stuck in orbit would ruin your whole day, so having a deorbit engine that was as foolproof as possible eased one of our perennial worries.

At time-zero the cockpit shuddered under the hammer of the two engines. Small bits of food crumbs, which had escaped our cleanup, drifted to the back wall. Hoot and Guy watched the computer displays of helium pressures, temperatures, and other indications of engine performance. They were all nominal.

The burn, and its acceleration on our bodies, ended. We were back in weightlessness. Hoot checked the residuals, which indicated the error of the maneuver. They were negligible. Whatever fate awaited us, we were now irrevocably committed. The OMS deorbit burn had clipped 200 miles per hour from our speed and changed our orbit so its low point was into the Earth’s atmosphere. There was no way we could climb back up to the temporary sanctuary of orbit.

According to the checklist I should have been strapped into the mid-deck seat, but there was nothing to do or see down there, so I had asked Hoot if I could hang out on the flight deck and shoot some video of the early part of reentry. I would get into my seat before the Gs got too high.

During the next twenty-five minutes we fell across the Indian Ocean, across the darkened continent of Australia, and shot into the night sky of the great Pacific basin. In our dive toward perigee, Atlantis gained back the velocity lost in the deorbit burn and added more. Shuttles achieved their peak speed on reentry, not ascent. The ride was as smooth and silent as oil on glass. The machine was on autopilot, with only her rear thruster jets active. Those were holding Atlantis’s nose 40 degrees high and presenting her wounded belly to the approaching atmosphere. Her aerodynamic control surfaces, the elevons on the wings and rudder on the tail, wouldn’t be able to hold her in attitude until we were much deeper into the atmosphere. If the rear thrusters failed, we would slowly drift out of attitude, tumble, and die. But an RCS system failure was far down on our lists of worries. The thruster jets were just smaller versions of the OMS engines, using a simple blow-down helium pressure feed system with propellants that burned on contact.

Hoot called the descent. “Mach 25.1…340,000 feet…Guidance looks great.” We were slightly faster than 25 times the speed of sound and at an altitude of 64 miles. Our little green bug was tracking perfectly down the center energy line. We were on course for Edwards AFB, still 5,000 miles away.

The atmosphere had thickened enough to become an obstacle to our hypersonic sled. Compression against Atlantis’s belly heated the air to a white-hot glow now visible from the front windows. I wondered what was happening underneath us. I had visions of molten aluminum being smeared backward like rain on a windshield. None of our instruments or computer displays showed Atlantis’s skin temperature. Only Houston had that data. I wondered if they would call us if they saw it rising. I hoped not. Such a call would definitely have us all tensed up as we died. Even Hoot wouldn’t be able to laugh away that MCC call. I looked at our displays and meters, not sure which would be the first to reveal a heat-shield problem. They were all in the green. Hoot would later tell me his eyes were never long from the elevon position indicators, certain a left-right split in those instruments would be the first hint the right wing was melting.

With the nominal displays I was happy to consider that our worries might have been misplaced. Maybe we had been alarmists. Maybe the damage was minor, as MCC had indicated. I still couldn’t believe that, but I prayed it was the case. I would have no problem offering the flight director, the CAPCOM, and everybody else an apology for having questioned their judgment.

“Three hundred ten thousand feet…still holding Mach 25…some Gs starting to build.”

Hoot didn’t have to tell me about the Gs. Dressed in my LES I had added more than sixty pounds to my body. My zero-G-acclimated muscles were finding it difficult to bear that weight against even a small G-load.

I looked upward through the top windows. As I had seen on STS-41D a snake of plasma flickered over us and slithered into the black. Periodically it would pulsate in incandescent-bright flashes that filled the cockpit like camera flashes. I wished I had paid more attention to the reentry light show during my Discovery mission. Wasn’t this plasma ribbon brighter? Weren’t those flashes more frequent? Was it Atlantis’s vaporized skin enhancing the show? There were no calls of distress from Hoot or Guy and the radios were mute. If the heat was dissolving Atlantis’s belly, the damage had yet to reach a system sensor.

At 240,000 feet and Mach 24.9 the guidance system commanded Atlantis into a 75-degree right bank. She was high on energy and the autopilot was pulling her off course to increase the distance to landing. In that extra distance we would have more time to descend. We trusted the autopilot to turn us back toward the Edwards AFB runway at the appropriate time. It was impossible for a shuttle pilot to look out the window at a featureless ocean from 45 miles high while still 3,000 miles from the runway and manually modulate the orbiter’s energy state. We had to trust the wizardry of accelerometers in Atlantis’s inertial measuring units to do that.

The plasma vortex intensified in brightness. I wondered how many earthlings were watching the celestial spectacle. The trail of superheated air would glow for many minutes after our passage. We were painting a white-hot arc from horizon to horizon to take away the breath of anybody watching, be they jungle island shaman or the crew of a supertanker.

The horizon came into view from Guy’s window. The Earth’s limb was tinted with the indigo of an impending sunrise.

“Mach 22 at 220,000 feet, a half-G.”

I wasn’t going to be able to stand much longer. My leg muscles were quivering. I had to get down the ladder to my seat. Before I left the flight deck, though, I craned my neck to see the Earth. The Sun had risen and painted a broken layer of clouds in flamingo pink. Just when I thought I had seen every “wow” scene in space, I was treated with a new feast for the eye. We were still traveling at a couple miles per second but had dropped to within forty miles of the cloud tops. The illusion was that we were accelerating, not slowing down. The clouds appeared to skim by at science-fiction speeds. The sight was a narcotic and I watched it until my zero-G-weakened legs couldn’t take my weight any longer and I collapsed to the floor. It was beyond time to get to my seat. I crawled to the mid-deck ladder like a wounded infantryman and felt with my feet for the ladder rungs. In slow, deliberate movements I worked my way downward and into my seat. By the time I was strapped in, I felt as if I had just descended the Hillary Step with a Sherpa on my back. I was exhausted from working in a G-force that was one half of the Earth’s pull.

I hated being downstairs. I was staring at a wall of lockers. There were no windows, no instruments. I felt claustrophobic. I could not imagine anything more terrifying than being in this room and hearing the death throes of a disintegrating shuttle while simultaneously having the lights and intercom go off, as had Ron McNair, Greg Jarvis, and Christa McAuliffe on Challenger. If the lights went dark and my intercom failed, I resolved to unstrap from my seat and try to climb upward so at least I could die looking out a window. There would be no reason to go to the side hatch and try our new bailout system. If I jumped out during aerodynamic heating, my body would be vaporized as quickly as a mosquito in a bug lamp.

I could hear rumbling through Atlantis’s structure. Again, I wished I had paid more attention on STS-41D. Was the rumbling normal wind noise?

We had glided 11,000 miles in the past 50 minutes but most of our deceleration was still ahead of us. Hoot’s dialogue came quicker. “Mach 20; 210,000 feet; 1,190 miles to go…Mach 18; 200,000 feet…one-G…185,000 feet; Mach 15.5…1.4 Gs.”

We had passed through the hottest part of reentry and Atlantis was flying just fine. Without a hiccup she was completing her transformation from spaceship to airship. My doubts about our assessment of the tile damage were growing and, again, I was happy to be alive to have those doubts.

Now there was significant wind noise accompanied with heavy vibrations.

“Speed brakes coming out.” We were ten minutes from landing.

At Mach 5 Guy activated the switches to deploy the air-data probes on the sides of the nose. The information they provided on airspeed and altitude would further refine Atlantis’s guidance.

“Mach 3.7…100,000 feet…I’ve got the lakebed in sight.” Atlantis’s computers had done their job. After a glide spanning half the Earth, they had put a runway within our reach.

The wind noise outside my little room had become a freight train roar.

“Mach 1.0…49,000 feet.” As Atlantis’s velocity dropped below the speed of sound our shock waves raced ahead of us, lashing the vehicle with a buzzing vibration. No doubt they were also sonic-booming the high desert and heralding our arrival to the wives.

We had finally entered the useable envelope of our crude bailout system. We were at subsonic velocity and below fifty thousand feet. If an escape became necessary now, I would pull the emergency cabin depressurization handle, followed by the hatch jettison handle. Then, I would unstrap from my seat, deploy the ceiling-mounted slide pole, clip my harness to a ring, and roll out. Of course all of this presupposed Hoot or the autopilot would be able to keep Atlantis flying in a straight-ahead, controlled glide. If the vehicle was in a tumble, the G-loads would pin us in the cockpit like bugs on a display board.

Hoot took control from the autopilot and banked Atlantis into a left turn toward final approach. Guy’s calls of airspeed and altitude came like an auctioneer’s. “Two hundred ninety-five knots, 800 feet…290…500 feet…400 feet…290…gear’s coming.” I heard and felt the nose landing gear being lowered. “Gear’s down…50 feet…250 knots…40…240…30 feet…20…10…5…touchdown at 205 knots.” We were safely home. Our heat shield had held. I was anxious to look at it and see how much crow we’d have to eat.

After the standard postlanding cockpit visit by the flight surgeon, we changed into our blue coveralls and walked down the steps from the side hatch. NASA Administrator James Fletcher was present to greet us. We exchanged handshakes and then turned to inspect Atlantis. There was already a knot of engineers gathered at the right forward fuselage shaking their heads in disbelief. The damage was much worse than any of us had expected. Technicians would eventually count seven hundred damaged tiles extending along half of Atlantis’s length. It was by far the greatest heat-shield damage recorded to date. Some of the more severely damaged tile had been melted deeper than the initial kinetic penetrations. The area around the missing tile had been particularly brutalized and the underlying aluminum looked as if it had been affected by the heat. But there had been no “zipper” effect, as the engineers had promised. If any of them had been present, I would have flung my arms around them and kissed them.

We had taken seven hundred bullets and lived to talk about it. The damage had been sustained in the only place where it could exist and still be survivable. It started a few yards back from the carbon-composite nose cap and stopped just a few feet short of the right wing’s leading-edge carbon panels. If any of those carbon-covered areas had been hit, we would have died as the Columbia crew would die fifteen years later, incinerated on reentry, except in our case the Pacific would have been our grave. Even the location of our missing tile proved fortuitous. By happenstance it covered an area where an antenna was mounted, and the underlying aluminum structure was thicker than in other locations. Had a different tile been blasted away, a skin burn-through might have occurred, allowing 2,000-degree plasma to run amuck inside Atlantis’s guts. God had watched after us. As Hoot turned from his inspection I heard him grumbling, “I’m going to be really interested in what MCC has to say about this.”

A few days later we got to hear their story. The quality of the TV images in Mission Control had been very poor. The engineers had been convinced the damage was localized and minor. I wanted to say, “You should have listened to us,” but they knew that. There was no reason to rub their noses in it. And then there was the nasty little fact that it didn’t really matter. Even if MCC had determined the damage would positively result in vehicle destruction and our deaths, what could have been done? Nothing. The ticket home always entailed a flight through the blast furnace of reentry. We couldn’t magically fly over, under, or around it. We couldn’t have repaired any damage. There was no space station outpost for us to have escaped to. Our only hope would have been to have another shuttle come to our rescue and we wouldn’t have had enough oxygen to wait for that. All we could have done was pitched the robot arm overboard and dumped every ounce of water and excess propellant to get our weight to a minimum to reduce the heat load, but even these efforts would have been in vain. Stripping the shuttle would have made the reentry just fractionally cooler. Just as it was with our contingency abort cue cards, any MCC recommendations would have just given us “something to read while we died.”

MCC did have an explanation for the failure of the SRB nose cone. There had been a change in the manufacturing process, intended to improve the performance of the ablative material that protected the SRB from the aerodynamic heating it encountered during launch. At our debriefing of the incident at the Monday astronaut meeting, others wondered how many other slide rule jockeys were violating the prime directive of engineering: “Better is the enemy of good enough. ” We all wanted to shout from the rooftops, “If it’s working, don’t fix it!”

At this same debriefing, Hoot reacquainted the post-docs with the sick humor of the fighter pilot. During our mission, there had been a horrific earthquake in the Soviet Eastern Bloc state of Armenia, killing 25,000 people. The TV news was still showing images of masked workers pulling bodies from the rubble. “I know many of you have been very curious about our classified payload.” Hoot paused until the room was hushed in expectation. “While I can’t go into its design features, I can say Armenia was our first target.” The military astronauts laughed. A handful of the post-docs cringed in disgust. Hoot tormented them further by adding, “And we only had the weapon set on stun!” The comment elicited more laughter and a few female darts of “Don’t you guys ever grow up?”