I was well into writing this piece when I learned of John Young's death on 1/5/18. I never had the opportunity to meet him during my time at NASA, but he was indeed a legendary figure at the Johnson Space Center. I encourage anyone with an interest in space history to research his incredible career. Ad Astra Mr. Young.
When Columbia fired its engines in April of 1981, crowds cheered NASA's first manned rocket launch in nearly six years. This was STS-1, the maiden mission of the space shuttle program. The system's reusable components promised to revolutionize spaceflight. No one watching the launch that morning had any way of predicting the highs and lows of the shuttle's three-decade career ahead. They weren't even sure that this crazy spaceship-glider was going to work at all. The columns of fire and noise lifting Columbia must have been reassuring, but not everything was unfolding according to plan.
Neither the astronauts racing skyward, nor flight controllers on the ground realized that Columbia had sustained significant damage in several locations during the first seconds of the launch. Any of these injuries could have led to a catastrophic failure. In fact, mission commander, John Young, later noted that he would have aborted the launch and ejected if he had known the extent of Columbia's maladies.
Exactly how the shuttle absorbed the hard knocks of its first launch and completed the mission safely is still not completely understood. The orbiter's robust design certainly contributed, as did the expertise within Mission Control and the astronaut corps. At the same time, it is difficult to analyze the specifics of STS-1 and completely discount the role of pure, dumb luck.
Trial By Fire
STS-1 was essentially a proof-of-concept mission. The idea was to exercise the main components of the incredibly complex shuttle and see if they worked the way engineers had predicted. As many as eight astronauts would eventually crew the shuttle, but only two seats were occupied on that first mission. Young shared the flight deck with pilot Robert Crippen. This marked the first time that humans were aboard the maiden flight of a US rocket.
In terms of learning about many of the shuttle's myriad idiosyncrasies, STS-1 can only be considered an unqualified success. A review of the mission's anomaly report reveals a laundry list of squawks that range in severity. Getting to the bottom of each issue was a vital step for continued operations. That never changed during the lifetime of the program. Some lessons were infinitely more costly than others.
The two anomalies that posed the greatest risk on that first flight affected the thermal protection and flight control systems of the orbiter. In both cases, the damage could be traced back to the same root cause: sound.
Damage to the shuttle was first revealed when Young and Crippen opened the payload bay doors in orbit. They detected missing thermal tiles around the Orbital Maneuvering System (OMS) rockets located at the base of the vertical tail surface. These silica tiles protected the orbiter's aluminum skeleton from the extreme heat of re-entry (up to 3000°F/1650°C) into Earth's atmosphere. The shuttle was literally covered with thousands such tiles. Each was a custom piece designed for the specific thermal, structural, and aerodynamic demands of its location.
The lost tiles were eventually attributed to acoustic energy on the launchpad. You can't expect to generate 7 million pounds of thrust without making a little noise too. The problem was that the acoustic energy produced by the shuttle's Solid Rocket Boosters (SRB) was significantly higher than predicted. The launchpad's sound suppression system couldn't cope. Excess energy reflected back onto the shuttle and knocked 16 tiles free while damaging another 148.
Ground controllers were not overly concerned about the missing tiles reported by Young and Crippen. That section of the shuttle would not be subjected to exceptional heating during re-entry. They calculated (correctly) that the missing tiles would not cause any significant problems.
The real anxiety felt by Mission Control revolved around the critical tiles on the belly of Columbia. Perhaps the same forces that had battered the OMS pods had also left their mark below. That question had to be answered before Columbia could return home. Flight controllers decided keep their tile-damage concerns from the crew unless they found damning evidence.
NASA's official story is that they called upon powerful ground-based telescopes to inspect Columbia. Some evidence suggests that NASA also coordinated with the National Reconnaissance Office to use spy satellites with cameras that could be pointed spaceward. Whether such assets were used, or even existed, has never been confirmed. Whatever methods were utilized, those on the ground were adequately satisfied that Columbia's tiles were in sufficient shape for re-entry. Young and Crippen remained blissfully unaware of the whole affair until after landing. Missing and damaged tiles would continue to plague the shuttle for the entirety of the program.
There actually were some issues regarding tiles on the underside of the orbiter. These problems were discovered after landing and attributed to improper tile installation rather than reflected acoustic energy. A plate that connected the shuttle to the large external tank became overheated and discolored during re-entry. These was also evidence of excessive heating around the landing gear doors on the nose and starboard wing. This caused items to fall free when the gear was deployed for landing and also created structural buckling on the starboard door. Fortunately, the rogue heating did not compromise the actual landing gear.
Following STS-1, NASA tweaked the launchpad sound suppression hardware. The uprated system dumped 350,000 gallons of water onto the launchpad in just 41 seconds. The water came not as a tidal wave, but a mist originating from numerous points. How this mist effectively absorbed sound energy is a topic worthy of an entire article. Top Gear fans will enjoy this great explanation by Richard Hammond.
Body Flap Flub
The body flap is a lip that protrudes rearward from the aft end of the orbiter's underside. It served two distinct purposes during the shuttle's landing phase. As the shuttle assumed a nose-high attitude and re-entered the upper atmosphere, the body flap provided heat protection for the Space Shuttle Main Engine (SSME) exhaust nozzles positioned above it. Once the orbiter got closer to the ground and transitioned into a glider, the articulating body flap worked in conjunction with elevons on the wings to provide pitch control.
Neither the body flap nor elevons were utilized during ascent. Vectored thrust from the SSMEs and SRBs provided all of the necessary attitude control. However, the checklist for the shuttle's launch countdown included an operational check of the body flap. It was actuated back and forth and then locked to prevent any movement during ascent.
When the SRBs fired for STS-1, the same wave of acoustic energy that punted thermal tiles also had its way with the body flap. Postflight analysis revealed that, despite being locked, the body flap had been strong-armed into positions significantly beyond its intended range of motion. NASA engineers agreed that this hyperextension should have damaged the hydraulic actuators and plumbing connected to the body flap….but it didn't. The body flap performed as intended during the remainder of ascent and landing. It was the spaceflight equivalent of falling off your roof and somehow landing on your feet without a scratch.
Nominal operation of the body flap was especially critical during the Shuttle's maiden re-entry. Engineer's predictions were slightly off regarding the elevon and body flap trim necessary to maintain the orbiter's attitude during the hypersonic gliding phase. This resulted in the body flap deflecting further than expected to keep Columbia within the landing profile. Adjustments were made to reduce the necessary body flap trim for subsequent flights.
It is not hard to imagine that a malfunctioning body flap would have been disastrous for Columbia and her crew. Assuming that they could have muscled through the remainder of launch and the re-entry portion of landing, control of the orbiter would have certainly been compromised while gliding. A successful landing being unlikely, the real question is whether Young and Crippen could have maintained adequate control to reach the narrow regime where their ejection seats (only available during the first four shuttle missions) were effective. The odds were not very favorable. Crippen even questioned the usefulness of the ejection seats with a properly-functioning control system. Let's all be glad that the body flap could take a punch.
Every Bit Helps
Spaceflight is inherently risky. That will never change. NASA spent ten years preparing for STS-1. Yet, Young and Crippen climbed aboard fully aware that countless variables remained…variables that could only be understood and addressed by taking the shuttle into space. Solid engineering had given them a ship with the best possible odds of success, but a healthy dose of luck helped bring them home.
All images appear courtesy of NASA
Terry is a freelance writer living in Buffalo, NY. Visit his website at TerryDunn.org and follow him on Twitter and Facebook. You can also hear Terry talk about RC hobbies as one of the hosts of the RC Roundtable podcast.