In the early days of the Space Shuttle program, NASA engineers faced a daunting challenge – how to rescue astronauts from a damaged orbiter in the event of an emergency. With the shuttle flying higher and faster than any previous crewed spacecraft, traditional escape systems like ejection seats or escape towers were deemed impractical. Instead, NASA turned to an unconventional solution – a fabric rescue ball called the Personal Rescue Enclosure (PRE) that would allow an astronaut to safely bail out of the shuttle and await pickup by a rescue vehicle. While the PRE never flew on an actual mission, it remains a fascinating chapter in the history of the shuttle program and a testament to NASA’s commitment to astronaut safety.
The Need for a Shuttle Rescue System
When the Space Shuttle was being designed in the 1970s, NASA initially did not plan for any way for the crew to escape in an emergency during launch or landing. The shuttle was seen as reliable and there was a desire to avoid the cost and weight of an escape system. However, as the first orbital flight tests approached, managers became concerned about the lack of options if something went wrong, especially during the risky initial launches.
NASA studied various crew escape concepts, including ejection seats, escape pods, and even having the astronauts strap on personal jet packs. But none were ideal – ejection seats couldn’t cover the shuttle’s full flight regime, pods would be too heavy, and jet packs too complex. What was needed was a relatively simple, lightweight system that could provide life support and protection for an astronaut bailing out at high altitudes and speeds.
Designing the Personal Rescue Enclosure
The solution NASA engineers came up with was the Personal Rescue Enclosure or PRE. Essentially a small fabric ball just big enough for an astronaut to curl up inside, the PRE could be quickly donned and provide protection from the airstream and life support until the astronaut reached an altitude where a personal parachute could be deployed.
The PRE consisted of three layers:
- An inner gas-retaining bladder made of urethane-coated nylon
- A structural restraint layer of Kevlar fabric
- An outer thermal protective layer made of Nomex felt
A small window made of Lexan allowed the astronaut to see out, while zippers allowed entry and exit. Inside was an emergency oxygen supply and lithium hydroxide canisters to scrub exhaled carbon dioxide, providing about an hour of life support. The entire unit weighed about 65 pounds (30 kg) and was roughly 36 inches (91 cm) in diameter when inflated.
To use the PRE, an astronaut would open a small hatch on the side of the shuttle cabin, pull themselves out into the airstream, and then curl up inside the ball as it inflated around them. The PRE would remain tethered to the shuttle until reaching an altitude of about 40,000 feet, at which point the astronaut would separate and free fall until deploying their personal parachute at around 15,000 feet for a final descent and splashdown in the ocean.
Testing the Rescue Ball Concept
To evaluate the feasibility of the PRE concept, NASA conducted extensive testing, including wind tunnel runs and high-altitude balloon drops. Dummies were used to simulate the forces an astronaut would experience during an emergency egress at various points along the shuttle’s flight path.
One of the key challenges was figuring out how to get the PRE and astronaut safely away from the orbiter without colliding with the wing or tail. The initial concept used a tractor rocket attached by a lanyard to pull the ball clear of the orbiter, but this proved problematic. Eventually, engineers settled on using a telescoping pole to push the PRE out and away from the shuttle before release.
Wind tunnel tests showed that the PRE was stable in free fall and generated a small amount of lift, which would help carry it away from the orbiter’s wake. Instrumented dummy drops from balloons proved that the forces during deployment and the opening shock of the parachute were within human tolerance limits.
NASA also evaluated different options for getting the astronauts in the PRE to a safe landing, including mid-air retrieval by helicopter and deploying the PRE with its own flotation system for a water landing. Ultimately, the baseline concept was for the astronauts to deploy their personal parachutes and use a life raft included in their survival gear for a water landing and pickup by rescue forces.
Limitations and Challenges
Despite the promising test results, the PRE still had significant limitations. It was only intended to be used during a small window of the shuttle’s ascent or descent when the orbiter was at a relatively low altitude and slow speed. During most of the climb to orbit, the shuttle would be going too fast for a safe bailout.
There were also concerns about how quickly the crew could egress the shuttle cabin and get into the PRE during an emergency. The orbiter only had one side hatch, so crew members would need to exit one at a time. NASA studies indicated it could take up to 90 seconds for each astronaut to depressurize the cabin, open the hatch, maneuver outside, and enter the PRE – a long time during a rapidly unfolding emergency.
The lack of any provision for the crew to escape during the shuttle’s high-speed ascent to orbit, where the risks were highest, was seen as a major shortcoming. But providing ejection seats or a separable crew capsule was ruled out as too costly and impractical to integrate into the orbiter’s compact cabin.
Another issue was that the PRE did not actually solve the problem of how to get the astronauts down safely from orbit if the shuttle was damaged or unable to return. The PRE was only usable during the earliest and latest phases of flight, not while the shuttle was in space. For a rescue from orbit, the crew would have to await the launch of a second shuttle, a capability NASA did not have at the time.
Aftermath of the Challenger Accident
On January 28, 1986, the Space Shuttle Challenger broke apart 73 seconds after launch, killing all seven crew members. The tragedy deeply shook NASA and forced a reexamination of many aspects of the shuttle program, including crew escape systems.
The Rogers Commission, which investigated the accident, was sharply critical of NASA’s decision not to provide a crew escape system for the shuttle. In its report, the commission stated: “The Shuttle Program management considered first-stage abort options and crew escape options several times during the history of the program, but because of limited utility, technical infeasibility, or program cost and schedule, no systems were implemented.”
In response to the commission’s recommendations, NASA initiated a major redesign of the shuttle to improve safety, including adding a crew bailout system. However, instead of the PRE, NASA opted for a simpler system that would allow the astronauts to bail out from a side hatch and parachute to earth, similar to the ejection systems used in military aircraft.
The new system, called the Inflight Crew Escape System, was installed on all remaining shuttles starting in 1988. It consisted of a pyrotechnic hatch jettison system, a telescoping escape pole, and modified parachutes and survival gear for the astronauts. While it still did not allow escape during the shuttle’s ascent, it provided a way for the crew to bail out during gliding flight if the orbiter was damaged but still controllable.
Summary
The Personal Rescue Enclosure never made it past the prototype stage and was not carried on any shuttle missions. With the implementation of the Inflight Crew Escape System after Challenger, the PRE concept was abandoned. However, it remains an interesting example of the innovative – and sometimes unusual – approaches NASA has considered over the years to keep astronauts safe.
While it had significant limitations, the PRE represented an attempt to provide a last-ditch escape option for shuttle crews during a period when none existed. Its development reflects the eternal tension in human spaceflight between the desire for safety and the constraints of physics, engineering, and budget.
As NASA looks towards new crewed spacecraft like the Orion capsule and commercial crew vehicles, the lessons learned from the shuttle program continue to inform the design of crew escape systems. From Apollo to the Space Shuttle to the vehicles of tomorrow, finding ways to protect astronauts and give them a fighting chance of survival in an emergency remains a critical priority. The story of the Personal Rescue Enclosure is a reminder of the challenges involved and the lengths that NASA has gone to in pursuit of that vital goal.