So look at the “Who takes the wheel?” question along three dimensions, as first set out by Scott Murray of NASA’s Johnson Space Center in Houston. They are Authority, Automation, and Autonomy.
Authority. Without the ability to exert control—using thrusters, gyroscopes, or futuristic gadgets—a spacecraft is little more than a hypersonic cannonball. If external influences like gravity, initial velocity, and air friction govern the flight, the other two considerations, automation and autonomy, are irrelevant. Sputnik was a spacecraft devoid of authority; it had no technology to change its trajectory. Mercury capsules gave the pilot the authority to change how it was pointed, as well as the option to trigger the retro-rockets needed for reentry—a good thing, since that part of the automation had problems.
But who, or what, employs the authority? That brings us to the second consideration. Automation: how much control humans exercise from moment to moment, and how much they hand off to machines. During the last minutes of each lunar-landing approach, Apollo astronauts used a good deal of manual control, but if some problem had required the approach be abandoned, they could have pushed a button to trigger a fully automated abort mode, boosting the lunar module back to rendezvous with the command module.
One part of spaceflight that is virtually always automated, and has been even from the earliest days: ascent from Earth to orbit. “When you’re riding a rocket, the thrust is so great, it’s hard to use manual control,” says Mike Burghardt. “Any small little mistake would easily send you off course.” But other aspects of the journey, such as the reentry of a winged craft or a lifting body like Sierra Nevada’s Dream Chaser, offer more choices about who drives. Exploratory missions venturing to the moon and beyond will pose many more choices, depending on the goals.
“[Design] decisions about the degree of human control—whether to automate something or not—are done on a case-by-case basis,” says John Goodman, a rendezvous and navigation engineer with United Space Alliance in Houston. The stereotype is that “engineers want to computerize everything” while “astronauts always want manual controls,” but it’s not always so. After Apollo 8, that crew suggested that the task of slowly rotating the spacecraft during the journey—necessary to prevent overheating on the sunlit side—be automated, so all three crew members could sleep at the same time. And upon his return, Apollo 11 command module pilot Michael Collins advised NASA to automate the tedious job requiring him to sit at the guidance-system keyboard and enter hundreds of digits, all error-free.
The third factor is Autonomy. How much freedom of action does the decision-maker in space have? If a spacecraft is going to a distant destination and is likely to encounter unforeseeable situations that will need a fast response, mission planners will dial up the onboard autonomy.
Planners have been giving communication-related autonomy to deep-space probes for years, so if the radio link to Earth is lost, the probe knows to lock down certain equipment in “safe” mode while firing up special routines to restore the link. Autonomy on any given spacecraft may be adjustable—called “sliding autonomy” in the trade—depending on tasks and events.
Questions of how much autonomy apply equally to manned craft. In 1965, the Gemini 8 capsule, having undocked from the Agena target vehicle, went into an uncommanded spin. Neil Armstrong and David Scott quickly identified the problem as a valve malfunction. Each second saw the rotational speed increase, and the control system couldn’t stop it. Adding to the crisis, the craft was out of radio touch and the astronauts were unable to get advice and telemetry analysis from mission control in Houston.
In true Right Stuff fashion, the crew rose to the emergency. With mere seconds before the spin would have made them black out, the astronauts fired the retro-rockets to stop the spin. According to mission rules, once the reaction control system had been used, an abort was required, so the pair headed back to Earth.
Story Musgrave, veteran of six shuttle missions and the only person to have flown in all five orbiters, dismisses the idea that manned spaceflight should be an independent venture. “A manned spacecraft isn’t autonomous,” he says. “Astronauts receive their orders from mission control. Pilots are part of a system, and the system can save your ass.” That system is not just hardware; it’s also rules, tests, training, and simulator runs. When things go wrong, astronauts benefit from the bigger system on Earth to help with analyzing and fixing the problem. In a manner of speaking, engineers go into space too: shoulder to shoulder with the astronauts, embodied in the machine they built.