this is the Cape. The President will be talking to you.” Caught by surprise himself, Glenn stammered, “Ah… the President? This is
Shepard said, “Go ahead, Mr. President.” The communications loop was dead; the call came early and the phone line was not yet patched in.
George Metcalf picked up the phone when it rang at his backroom console. He thought it was a gag when the voice at the other end said, “This is the White House, stand by for the President.” Attending other duties and unaware of the planned phone call, George stuttered, “Hello, hello, Mr. President!” Then Metcalf stood up, wildly gesturing for other technicians to come help him set up the patch.
In the control room, a more crucial event now intruded on the team’s attention. A warning light had flashed on the instrument panels in Mercury Control. Moments later, Don Arabian, the systems monitor, called out, “Chris, I don’t know what to make of this, but I am showing an indication on Segment 51.”
Kraft looked perplexed. I overheard the call and immediately pulled out the telemetry listing from my console drawer. “Chris,” Arabian went on, “Segment 51 is the impact [landing] bag deploy.”
Quickly, I called John Hatcher, the facility team boss. “John, forget the [President’s] phone call and verify the patching of Segment 51.” Then I broadcast an all-site Teletype message: “Confirm patching instructions for spacecraft telemetry and report the readings on Segment 51, ASAP.” The chilling implication of the telemetry that Don Arabian was reporting was that the impact bag had deployed—which in turn meant that the heat shield had somehow come loose. The heat shield protects the capsule from the fire of reentry. After reentry is complete and the parachute is deployed, the heat shield is released. A rubberized bag which is attached to the capsule structure is stowed behind the heat shield. After the capsule’s parachute deploys the heat shield is automatically released and the rubber landing bag extends to cushion the landing impact. On the water the landing bag acts like a sea anchor to stabilize the capsule in the upright position and minimize drift.
If the telemetry indication being reported was correct and the heat shield had come loose in orbit John Glenn would have no protection from the 3,000-degree F reentry temperatures. The capsule would become a meteor that flashed for but a few brief seconds during reentry before burning up.
Kraft and the team were now faced with a grim set of choices. Controllers, distrustful of solitary measurements, immediately started digging out the details of the switch and how it was rigged. The phone system came alive as the problem was pursued. Precious time was lost trying to track down engineers at the blockhouse and Hangar S. Kraft’s controllers had no provisions for emergency access to the total design, manufacturing, and assembly team. I jotted a note to myself to set up a hot line to McDonnell Aircraft for the next mission—if there was one.
Unaware of the crisis unfolding around him, John Glenn coasted over the Atlantic. He was oblivious to the uncertainty over Segment 51, but he was now having an unrelated problem with the attitude control. The capsule was drifting sideways to the right until it hit the attitude limit, then the big yaw thruster would kick in.
The mood inside Mercury Control had changed with the suddenness of a thunderclap. Metcalf, still holding the line to the White House, found no easy way to disengage. “Mr. President,” he blurted, “we’ve gotten pretty busy down here now. I don’t think we’ve got time to talk.” The President responded, “Give me a call if you get a chance.” George hung up and turned to more urgent problems.
As the spacecraft passed over Central Africa, Glenn reported that he was departing from the flight plan and was troubleshooting the attitude control problems. It appeared to him and those on the ground that the problem was a random movement from left to right, possibly caused by one of the small thrusters working intermittently.
Glenn interrupted his troubleshooting with reports on the flight plan as he moved across the Indian Ocean, continuing his assurances to the doctors that he felt fine. The medical community’s anxieties, although reduced by Yuri Gagarin’s one-orbit mission, persisted. Kraft and the rest of the control team were elated with Glenn’s performance. It was obvious that he was on schedule and had no problems adapting. As John passed over Australia, he embraced the attitude control problem with an energized can-do spirit.
On the ground the story was far different. The blockhouse had reviewed their measurements and verified that they had had no Segment 51 indications during launch. But when the spacecraft passed overhead at the end of the first orbit, the blockhouse had seen the indication also. The data I was receiving from the remote sites was not much help. Half of the CapCom reports indicated they were seeing Segment 51, and the others were not.
The limitations of the Mercury communications system now became evident. The response to each of the Teletype queries took ten to fifteen minutes. The answers often prompted another query.
Chris was now on the phone with the blockhouse, trying to get answers, while I had gone to a small office behind the Teletype room seeking out Ed Nieman and Dana Boatman, the two McDonnell engineers who were developing the system schematics. Both of us were seeking answers to the same question: if Segment 51 is valid, what are we going to do about it?
Chris was not having much luck and his frustration level was rising. The design engineers, in the heat of real-time crisis, weren’t quick at coming up with options. One of them suggested, “Let’s make sure Glenn keeps the landing bag switch off and we should ask him if he hears any banging noises when he maneuvers at a high rate.”
Kraft relayed the messages to Gordo Cooper in Australia, who first verified the landing bag switch position. Cooper asked, “John, you haven’t heard any banging noises or anything of that kind, have you? Maybe when you maneuver at a high rate?” Glenn replied, “Negative,” and let the question drop. If he found it strange, he gave no indication.
Walt Williams, Max Faget, the capsule designer, and John Yardley from McDonnell now joined Kraft at the console. In short order, the words came tumbling out, like objects falling from a filled closet. Faget proposed to hold the heat shield in place for the early part of reentry with the retropack.
The retropack is a cluster of three solid rockets used to reduce the orbital velocity sufficiently to allow gravity to pull the spacecraft into a safe reentry trajectory. The timing of the retrorocket firing and the spacecraft attitudes are key to hitting the planned landing zone. The retropack is located behind and in the center of the heat shield and is attached to the capsule by three metal straps. After the retrorockets are fired, an electrical signal pyrotechnically cuts the three straps and a small spring pushes the empty retropack away from the heat shield. With the capsule oriented blunt end forward during reentry, the heat shield protects the capsule by dissipating the heat as the capsule enters the atmosphere. The heat shield literally melts away (ablates) on reentry. If the heat shield was not firmly attached to the capsule the aerodynamic forces would tear it off during reentry, leaving the capsule unprotected. If after retrofire, however, the retropack was not jettisoned, it was in a position to hold the heat shield during the reentry until the retropack melted away. When the retropack melted it was believed the aerodynamic forces would hold the heatshield in position during the remainder of the reentry.
I looked around the room and saw faces drained of blood. John Glenn’s life was in peril. We were desperate to find a solution, without being sure we knew the problem.
Kraft said, “This is the wrong way to go. It’s too damn risky for something that is probably an instrument error.” Fighting to avoid a premature decision, Kraft fired off a barrage of questions: “Does anyone know the aerodynamic effects of reentering with the retropackage attached? Do we have sufficient control with the attitude jets to keep us oriented in reentry attitude? Will we damage the heat shield to the point where it cannot protect the capsule as the retropack melts away during reentry?” Faget and Yardley scratched their heads. They were well beyond the bounds of their design knowledge.
Faget, quietly muttering in his Cajun accent, tried to reassure Kraft. “Chris, it should be okay. We designed the heat shield with plenty of margin.” His words did not sound convincing. Kraft’s gut feeling indicated just the opposite. He believed Segment 51 was a false telemetry indication and the risks of an unproven, untested entry technique with the retropack were too high. Kraft exclaimed, “Dammit, we’ve got to find other pieces of data to confirm this before we jump to the conclusion to enter with the retropack.”
Slayton and Shepard had plugged into Kraft’s console for the telephone conversation with the blockhouse. Returning to his console, Williams leaned over and asked, “What should we tell John?” Kraft ignored the question for the moment.
Faget, the consummate engineer, could not ignore the telemetry. Engineers like Max live by their data. Asking one of them to consider that the telemetry information may be wrong borders on the heretical. Kraft was at the opposite end of the spectrum. “Max, dammit,” he barked, “we only got one piece of instrumentation. My guys tell me it would take a dual electrical failure for the heat shield to come loose. The way it is stacked, a mechanical
