“One thing Skylab taught is that we should glance back from time to time to avoid old mistakes and gain inspiration from old successes. But to move forward into the future, we don’t need to revive the past.”
Chapter 4: Crawling
Bathed in the light of a dozen xenon arc lamps, MLP-3, bearing atop it the Launch Umbilical Tower and the 30-story-tall Shuttle stack, began its journey out to the launch pad hours before dawn. Engineers and technicians walked with it out to the pad, easily matching the ponderous pace of the nearly 8,000 tonne stack. Smoky diesel exhaust trailed out of the Crawler’s vents, as the four 1 MW engines labored to drive the massive tracks that distributed the vehicle’s weight across the sandy crawlerway and kept it from sinking into the soft Florida soil. It was a routine that the engineers had practiced many times on earlier flights, and on Apollo and Skylab before them, and planned to practice many times again. But, given the payload of this flight, there was understandably more attention to detail—not one nut out of place that anyone on the ground could see.
Hours passed. The sun’s light reached over the horizon, reflecting off the undersides of distant clouds to cast orange light onto the Vehicle Assembly Building and then the stack. Then, like a rocket engine reaching full thrust, the sun itself crossed the horizon, and the light of the xenon lamps was drowned in a much brighter glare.
At last, shortly after dawn, the stack reached LC-39A, and the crawler deposited the 5,000-tonne pad, tower, and vehicle combination on the raised concrete foundation. Then it drove back to the VAB—its job was not yet done, for there was still the Mobile Servicing Structure to bring over, the tall gray tower whose platforms gave technicians access to the vehicle as it stood on the pad. Another hour and a half to drive back to the MSS, another hour and a half to bring it over to LC-39A. By the time the crawler’s job was done, dawn had given way to a beautiful Florida morning.
Launch was still several days off—now came the time for final check-out, as each spacecraft component was put through its last ground tests. Telemetry was checked, temperatures on major components were inspected, radio tests were performed, and technicians made last-minute inspections inside the cockpits of each vehicle to make sure nothing had changed between stacking and arrival at the pad.
An alarm went off—the fill test of the S-IVC had revealed a leaky hydrogen line in the interstage. There was a buildup of hydrogen gas in the interstage—dangerous enough on its own, but in close proximity to two oxygen tanks, it was worse. The test was terminated immediately, the tanks given time to vent, and technicians opened access panels around the base of the stage to inspect. Could the lines be repaired on-site? That was the preferred option—rolling back to the VAB was a time-consuming nuisance. But if the problem was severe enough, the vehicle would have to be de-stacked, and the stage either repaired or—heaven forbid! thought the launch operations director—replaced with a new S-IVC, costing even more time.
Luckily, the McDonnell-Douglas technicians were able to isolate the problem and correct it. The test was repeated less than a day later, with no apparent hydrogen build-up. The tests continued, each system checked out properly, and the launch operations director allowed himself the luxury of optimism—perhaps this first mission of the Shuttle would go off on-time!
Alas, a new issue came up, one which all the technicians at the Cape were powerless to solve. NOAA and the USAF both warned about a line of severe thunderstorms crossing Florida. In normal circumstances, the stack would have remained on the pad—the lightning rods surrounding it would protect it from electrical disturbances, and the Booster was durable enough to take a little hail. But the Orbiter, with its exposed tile thermal protection, was an unknown variable. Putting it at risk to save a few days was out of the question—the director reluctantly ordered a full rollback to the safety of the cavernous VAB.
At times like this, he thought as he finished his morning coffee while monitoring the rollback, he regretted that White Sands had not been chosen as the main Shuttle launch site.
When the storms cleared, the dance of the lumbering giants was repeated, and the Space Shuttle stack finally occupied the pad again on July 21, 1980.
As each of the major STS contracts was assigned, the prime contractors began the monumental task of developing and testing a reusable spacecraft system. Though not quite as complex and uncharted a task as the Apollo program, the Space Transportation System gave its contractors and program heads a great deal of grief before its first operational flights. The process began in 1972, with the awarding of the contracts for the Booster and Interim Upper Stage vehicles. These were the best-characterized of the three main STS components, and so metal-cutting could begin on them long before the Orbiter was ready.
The S-IVC was the most straightforward component. During the selection process for the Space Lifter upper stage, Douglas had proposed a number of changes to the S-IVB much more extreme than a simple stretch. Some of these changes, like the shift from internal tile-based insulation to external spray-on insulation, stemmed from the experience acquired by the American aerospace industry by building three different stages that used cryogenic hydrogen for Project Apollo. Each of the three different cryogenic stages developed in the 1960s--Centaur, S-II, and S-IV/S-IVB--used wildly different construction techniques. Centaur was a pressure-stabilized stainless steel balloon--without constant pressurization, the stage would collapse under its own weight (as the closely-related Atlas stage collapsed during preparation for the launch of Mariner 6 in 1969), with four external insulation panels and two RL-10 engines. S-II and S-IVB used much more conventional construction techniques, at the cost of greater weight, and used the much more potent J-2 engines. The S-IVB stage used a complicated system of custom-made tiles to insulate its liquid hydrogen tank, which had to be applied to the inside of the tank in a time-consuming process. The S-II had originally been designed to use a honeycomb-panel insulation system, with large sections of insulation secured to the outer surface, but the extreme cold of cryogenic hydrogen had a tendency to liquefy air pockets trapped between the insulation and the rocket, weakening the bond and causing panels to fall loose. The helium-based purge system North American introduced never worked very well, and, starting with the S-II stage for Apollo 13, the company shifted to a spray-on insulation that eliminated bonding agents and air pockets entirely.
Douglas’s engineers were very well-aware of these changes even as the Apollo program wound down, and incorporated many of the design innovations from S-II and Centaur into their proposals for S-IVC. The intricate tile-based insulation would be thrown out in favor of spray-on foam, and control software developed for Centaur to enable navigation in less-than-ideal weather would be adapted to the Saturn Instrument Unit. The loss of J-2 engines on two separate Saturn V launches led them to propose the addition of a second J-2S-2 on the S-IVC, producing a stage that came to resemble a gigantic Centaur. Though they (and Rocketdyne) argued vigorously that the second engine on each stage increased redundancy while also offering economies of scale in engine production, NASA’s focus on mission costs led to the S-IVC proposal scaling back to one J-2S-2 per stage. Thus, the final S-IVC involved little of the originally planned new technologies. Even its upgraded J-2S engine, with the exception of the proposed new nozzle, had already seen the test stand before the end of the Apollo program in December of 1972. Its challenges were more in the field of logistics and cost-control. McDonnell-Douglas worked diligently to implement the cost-cutting measures of the “Chinese Copy” plan, reducing handling and increasing automation. Though it lacked the missile-manufacturing experience of rivals like Martin Marietta and Convair, McDonnell-Douglas adapted several automation techniques used in its airliner business to the S-IVC, more-or-less achieving the manufacturing cost savings it had planned for. After some internal argument, the company elected to mothball its own Sacramento test site rather than upgrade it to handle the S-IVC, and trust in Rocketdyne to supply functional J-2S-2 engines. Test-firings of the fully-assembled S-IVC would be performed only at Stennis Space Center.
A greater headache was actually transporting the stage from Huntington Beach, California to Cape Canaveral. The S-IVC’s stretched length left it too long to fit inside any of the Guppy-derived aircraft NASA had preferred for S-IVB delivery. Though Douglas had barged some S-IVBs in the 1960s, they did not relish the long travel times that that approach required. Furthermore, in recognition of the fact that Shuttle was supposed to fly at least a dozen times per year, it was necessary to be able to have S-IVC stages ready to mount on a Space Lifter at any time, in case there was some anomaly that required swapping-out stages, or a time-critical emergency payload. McDonnell-Douglas and NASA ultimately invested in a new, larger barge, which could carry four S-IVC stages at a time through the Panama Canal or to Vandenburg Air Force Base, allowing either launch site to maintain a surplus of upper stages at any time. The first S-IVC test stage was fired in 1977 at Stennis Space Center, and was then sent on to Marshall Space Flight Center for storage in case it was required for an accident investigation.
The Space Lifter was the single largest and heaviest component of the Space Transportation System, and the one with the strictest reliability requirements. Unlike the Orbiter, which would fly only a fraction of the total STS missions, and the S-IVC, which did not always carry a crew, the Space Lifter had to succeed at its goal for both mission success and astronaut survival. NASA thus required an extensive testing program, including piloted abort missions and one destructive test to verify the operation of the escape pod. In order to streamline development and get to flight-testing sooner, Boeing engineers at Marshall Space Flight Center converted several remaining S-IC test articles into RS-IC test articles, retrofitting them with wings, landing gear, and (initially) dummy flight decks. The first prototype (RS-IC-F), formerly the fit-test S-IC that debuted at Cape Canaveral in 1966, was retrofitted at Marshall and rolled out of its hangar there in June of 1975, rolling down to the Tennessee River for barging down to Stennis Space Center and on to Kennedy and Vandenburg for fit-tests. This one lacked a functional flight deck, but conveyed the overall dimensions of the vehicle well enough for that task.
1974 saw the first major redesign to the Space Lifter--the elimination of the retracting nose and addition of a disposable shroud between the Booster and the upper stage. In the near-hypersonic flight regime of the Space Lifter during descent, a failure of the nose to extend would lead to catastrophic stagnation of airflow in the confined area of the nose--which would cause immense heating in the unshielded interior of the spacecraft. Computational Fluid Dynamics testing, performed on the finest computers available at the time painted (metaphorically--graphical outputs were beyond their capabilities) a grim picture, with loss-of-vehicle in almost every failed retraction scenario. Boeing could not guarantee a failure-proof hydraulic or spring-loaded extension mechanism, and so opted for a triple-redundant pyrotechnic bolt to jettison a traditional interstage over a smooth, fixed nose. The cavernous volume of the Space Lifter’s nose would vex Boeing engineers for years after this decision--it cried out for utilization, for extra propellant tanks or other efficient use, but issues with mass distribution and changes of mass in flight precluded that. It fell to an enterprising young woman with NASA’s Education Office to propose the Student Suborbital Experiment Bay, which has carried hundreds of experiments from High School and University students past the Karman Line and exposed them to microgravity for several minutes at a time.
The first Booster actually destined for flight, RS-IC-601, actually rolled off the assembly line on June 17, 1976. RS-IC-601 went on a cross-country tour at the end of June, visiting several major civilian airports, culminating in a landing at Washington National Airport on July 4, where, in celebration of the American Bicentennial, President Ford christened her “Independence.” Still without functional rocket engines (indeed, still without quite a few of the systems that would get her ready for suborbital flight), she was put through a subsonic and then low-supersonic flight-test program to verify low-speed handling and the ability of the spacecraft to successfully navigate to a landing. Ken Mattingly, who commanded the Atmospheric Test Flights, had few kind things to say about the vehicle’s performance--”It’s like flying a brick,” he complained. But it did the job it had to do.
While all seemed well with the Booster, the Orbiter’s comparatively advanced technologies, particularly the lifting-body shape and tile-based thermal protection system, gave North American’s engineers no end of headaches. By the end of 1976, it had become apparent that the Orbiter would not be ready in time for its planned 1978 debut. As NASA prepared for the imminent change in administrations, this was very unwelcome news, but would have been a mere nuisance were it not for the publication, in 1977, by NOAA of solar activity predictions that predicted severe heating in the upper atmosphere. NORAD quickly followed up with a prediction that the Skylab space station, which had been quiescent in orbit since 1973, would reenter, not in 1981 as expected, but in 1979.
NASA had planned to reboost Skylab with an early Shuttle mission, to test out the rendezvous and docking capability of the Orbiter, to demonstrate attachment of the Reboost Module from the payload bay to Skylab’s docking port, and to obtain samples of a vehicle left in space for over half a decade. But between the delays on the Orbiter and the imminent demise of Skylab, these plans seemed to be going down in flames.
1977 thus saw a frenzy of mission planning at every major NASA center, as options were evaluated for saving Skylab by somehow advancing the Space Transportation System’s schedule. These ranged from the semi-plausible (reconfiguring one of the launch pads at Cape Canaveral to fly a Saturn IB/Apollo spacecraft, which by this point would have to be taken back from the museums to which they’d been handed) to the uncertainly safe (flying Space Lifter with an Apollo spacecraft as a payload, without going through NASA’s planned suborbital and abort test regime) to the expensive (flying a Space Lifter unmanned as in a conventional Saturn V mission, with an Apollo payload and dumping the booster into the ocean) to the downright bizarre (one proposal suggested using surplus Gemini spacecraft launched off a Titan II pad to reboost Skylab). There also emerged at this time a proposal to launch Skylab B, which had been handed over to the National Air and Space Museum but not yet fully “decommissioned” for museum display, but this proposal was perhaps the most expensive of all.
Ultimately, budget overruns on the Orbiter and lack of attention from President Carter meant that each of these proposals was simply more expensive than Skylab, decrepit and aged, was deemed to be worth. NASA planners expected that, once both were flying, development funds could be spent on a more mature Skylab follow-on, one that would meet the desires of the Apollo Applications Program planners in the late 1960s (memoranda circulated at Ames Research Center, for example, proposed modifying an S-IVC into a tumbling artificial gravity experiment--long a goal of the 1960s). When measured against the need to make sure Shuttle was completed and the possibilities the 1980s yet held, Skylab was found wanting. All the same, the loss of a station that still seemed, to many researchers, perfectly viable left a bad taste in many mouths, and contributed to an unnecessary amount of bureaucratic infighting over the experimental Space Stations of the 1980s.
1977 came and went without funds for Skylab. As that year progressed,
Independence was outfitted with more equipment necessary for flight testing, and her sister ship, RS-IC-602
Constitution joined her in the testing fleet. They were briefly joined by an unnamed vehicle, numbered RS-IC-599, whose purpose was to fly the Suborbital Escape Pod Demonstration Test. This mission would see the stage, carrying a dummy second stage and payload, fly unmanned, with crash-test dummies lined with accelerometers occupying the seats in the flight deck. After staging, the flight deck would be jettisoned, to test the ability of the escape pod to recover the crew safely in the event of a suborbital bail-out. The escape pod had to be a spacecraft in its own right, with a closed environment and its own heat shield and landing system for oceanic splashdown.
September 28, 1977 saw the launch of this officially-unnamed vehicle (though photos released after launch revealed that pad technicians from either Boeing, Grumman, or NASA had chalked the words “Sacrificial Lamb” under the cockpit windscreen), and the first use of the escape pod in flight. The flight deck splashed down about 150 km downrange of Kennedy Space Center, and was recovered by the US Coast Guard for analysis. The dummies were no worse for wear, though the accelerometers revealed a painful 8-G reentry. Better bruised than broiled, though--actual astronauts would have survived that flight. The name inscribed in chalk, sadly, was nowhere to be found--either scorched off on ascent, during reentry, or washed off in seawater. With the flight of the escape pod, the Space Lifter was deemed man-rated.
Sacrificial Lamb continued her flight after the loss of her flight deck, continuing on automated commands to reenter without a deceleration burn. Heavily instrumented, she transmitted her condition to Boeing and NASA researchers eager to study the effects of hypersonic reentry on such a large vehicle. They hoped against hope that she’d make it down to the ocean for recovery, but sadly this was not to be. Partial telemetry was tracked by US Navy and Coast Guard assets standing by after the main portion of entry, but maximum temperatures were close to the failure limits of aluminum structures. With no pilot at the controls, what might have been chancy for a human was outright impossible. The breakup of the Lamb at Mach 4 was recorded by US Navy radar and relayed back to NASA--setting a record for the fastest recorded glider accident.
October 12, 1977, saw the first manned launch of the Space Lifter
Independence, on a suborbital demo flight, carrying a dummy second stage (loaded with liquid hydrogen, to simulate the proper weight distribution) and a dummy payload. The mission proceeded without a hitch--at 180 seconds into the flight, the engines shut down, and pyrotechnic bolts jettisoned the dummy payload, which was destroyed by range safety officers after the Booster’s deceleration burn. Entering the atmosphere at 1.5 km/s, Commander John Young and his Copilot, Dr. Story Musgrave, piloted
Independence to a safe landing at the Shuttle Landing Facility at Kennedy Space Center. STS-A, the first manned test flight of the Shuttle system, was complete.
1978 saw the first orbital test flight of the Space Lifter stack, when STS-B, crewed by Ken Mattingly and William Thornton flew
Constitution with a functional S-IVC upper stage. During this flight on March 19, they delivered an inert 40,000 kg mass simulator into a very low orbit. After a single orbital pass to confirm parking orbit accuracy with ground radars, the SIV-C reignited to lower its orbit and dump the dummy payload into the ocean. In addition to mitigating debris, this proved the ability to relight the S-IVC for additional burns in space on geostationary launches. The successful orbital test briefly renewed hopes that Skylab could yet be recovered, but the time necessary to restore an Apollo CSM to working order and train a crew for the task was deemed too great.
After this, as NASA worked to prepare the Shuttle’s actual satellite payloads for flight in 1979, the rest of 1978 was spent going through abort scenarios with inert upper stages. STS-C, -D, and -E went through abort scenarios designed with recovery of the Booster, if not the payload, in mind--the first, simulating engine failure close to the end of the Booster’s ascent, was the most benign. The second, conversely, was the most hazardous--engine shutdown at maximum dynamic pressure, the point where aerodynamic stresses on the stack were maximized. This profile called for ignition of the jet engines during ascent, allowing the stage to coast up past the jettisoned upper stage and payload, until the vehicle came down to a manageable flight regime, while the upper stage fell into the Atlantic. Finally, STS-E demonstrated a partial engine shutdown--loss of an outboard engine during ascent. The loss was compensated by shutdown of the engine across from it, giving the vehicle enough thrust to continue ascent to a safe jettison point, but not enough to successfully complete the mission.
With the completion of the Suborbital and Abort Test Program, Space Transportation System missions switched from assigned letters to flights to assigning numbers. STS-1 was scheduled for early 1979, the first operational flight of the Space Lifter stack, albeit without an Orbiter.
