Bringing Down a New Bird: Landing Gemini

I’ve previously discussed NASA’s invention of a landing system for the Mercury program – with little time and almost no prior experience, engineers determined that splashdowns were the simplest and least risky method to bring an astronaut home. But, as I’ve also previously discussed, splashdowns were far from an ideal landing method; inherently dangerous to both astronaut and capsule alike. (Left, a half-scale Rogallo wing mated to a half-scale Gemini spacecraft. NASA Archives.)

NASA’s second-generation Gemini program opened the door for a change in landing methods. Though incepted in early 1962, work on the program began late in 1961 when the end-of-decade lunar landing goal was seemingly far away. Gemini, then, had a more open schedule at the outset, allowing engineers to undertake some major design changes. One of the first aspects of Mercury to go was splashdown. The original goals for Gemini stated that a pilot-controlled land landing was paramount. So the program began seeking an answer to the question of how to invent a land landing system.

Land landings from space weren’t entirely unheard of when Gemini planners began considering different systems for the program. Mercury planners had briefly considered land landing systems in the initial planning stages before time constraints took over. Across the ocean, the Soviets had been landing exclusively on land from the beginning. How hard could it be?

When the initial landing system proposals came to NASA for Mercury, only one focussing on land landings – a proposal from the research group at Langley Air Force Base for a deployable wing that could turn the capsule into a controllable gliding vehicle. The proposal was known as the paraglider, or the Rogallo wing after its inventor.

The idea was the brainchild of engineer and amateur kite-flyer Francis M. Rogallo (left, with his wife) who had been working on flexible wing designs since 1948. Rogallo was confident that if he were able to develop a means of storing and deploying such a wing, the device could eventually replace parachutes and rigid wings alike as an all-around landing system. In 1958, Rogallo presented his design to the Research Committee at Langley and was promptly given a lab in which to pursue his work on the paraglider concept.

Within months of Rogallo’s partnership with Langley, the latter saw sufficient potential in the paraglider idea to present the wing to NASA as their bid for the Mercury landing contract – the final design they presented to NASA was a two-lobe, single-curvature, suspension-load wing that combined the benefits of a parachute with the rigid flexiblily common in airplane wings. The budding space race, it seemed, was providing Rogallo with a perfect environment to prove his concept.

Rogallo with a model of his paraglider wing. 1959.

The method was, for the inaugural Mercury program, to complicated. At least in the first stages of US spaceflight, developing a reliable way to leave the Earth was much more important than how the astronaut came back. Splashdowns won the Mercury bid by default.

The Rogallo wing, however, was an interesting and promising system, even if it was impractical for Mercury. NASA Administrator Robert Gilruth (right), firmly convinced that the design would have a future in spaceflight, approved research on the paraglider in 1960. It was not assigned to any program in particular, but had a home within NASA. When Gemini began moving away from splashdowns, the Rogallo wing was already on the table. But it certainly wasn’t the only method up for consideration.

NASA considered a number of landing options. Some were closer to the ballistic capsule exemplified by Mercury splashdowns while other proposals were closer to the aerodynamic gliding landing used in the X-15 program. Four proposals eventually reached the final round of testing.

One proposal was for a parachute-controlled descent. The spacecraft would be slowed in its initial descent using parachutes, and retro rockets would fire in the final moments to before touchdown to complete a gentle landing. But the method was more complicated than it seemed. Part of the problem was the weight of this system. The Gemini spacecraft was only slightly bigger than Mercury and the Titan launch vehicle only slightly more powerful than the Atlas used in Mercury orbital flights. It was impossible for NASA to lift a spacecraft with the requisite fuel and rocket system into orbit.

A variation on this method was ejection, the same system used by the Soviet cosmonauts. For Gemini, ejection would use the same parachute to slow the spacecraft, but the astronaut would eject just prior to impact. His final return to earth would be by an individual parachute.

Another proposal centred on a manoeuvrable parachute or parasail. The parasail would function like a parachute in the early stages of the descent, giving the astronaut increased directional control of the spacecraft as the atmosphere thickened. The problem with this method was the limited control the astronaut would have. While he would be able to manoeuvre the spacecraft to avoid local objects, the parasail was really more of a controlled fall than a truly pilotable landing.

The limited control meant that the astronaut still needed a very controlled landing zone for a safe touchdown. Furthermore, the parasail system employed no additional brakes, no directional stability during descent, and was not inherently stable upon landing. A strong wind could easily catch the sail and cause the spacecraft to tumble.

With both the parachute and parasail landing methods, there was no means to incorporate backup safety measures. Furthermore, there were dangers associated with a hot spacecraft landing on land. The ablative heat shield used in Mercury and included in the Gemini design absorbed the heat produced from friction with the atmosphere before burning off, thus protecting the astronaut inside. But the spacecraft would still hot when it landed. There was a very real danger of prairie or forest fires, hardly the safe environment NASA wanted for its astronauts.

A third possible landing method used the aerodynamic properties of the spacecraft to affect a controlled land landing, otherwise known as the lifting body proposal (three styles of which are pictured). An aerodynamically designed wingless spacecraft produces sufficient lift, enabling the astronaut a fair bit of control through the descent and landing stages. By virtue of its design, the spacecraft essentially becomes a glider. This landing method was similar to the X-15, adding significant control to descent and stability in landing with no risk of tumbling upon landing. A gust of wind was unlikely to be able to displace a solid body spacecraft.

A final proposal was the Rogallo wing – the exact system proposed for the Mercury program the Langley research group, which was at the time under development for some as-of-yet undeveloped project. The wing offered enough manoeuvrability to negate the need for a controlled landing area while also being sufficiently lightweight to be easily incorporated into the Mercury-inspired Gemini spacecraft. Because it was designed to land like an airplane, landing gear was necessary for a safe and directionally stable landing.

A schematic representation of the reentry, descent, and landing of a Gemini-paraglider configuration. NASA Archives.

Increasing testing gradually narrowed the list of finalists. Ejection was one of the first to go; it was unpopular with the astronauts despite its success with their Soviet counterparts. As test pilots, parachutes were associated with a failed landing or a disaster. No pilot-turned-astronaut wanted to be separated from his craft, return to earth at the mercy of the winds, and have no possible way to control his landing position.  It was far from ideal.

Parachute-controlled descent, too, was an unpopular option despite their proven reliability in splashdowns. The stigma of parachutes was equally present with a land landing, even if the astronaut remained inside the spacecraft.

The lifting bodies method was also quickly dismissed. In a chart outlining and comparing the performance, cost, and test results of the four previously mentioned landing methods, head of the Gemini Program Office Jim Chamberlin made his disapproval of the method clear. Hw didn’t bother comparing lifting bodies with the other three methods. Instead, he described the weight penalty simply as “large” and the cost as “high”.

Part of what killed the lifting bodies proposal – arguably the preferred design for a vehicle returning from space for its control and stability – was the design of the spacecraft. The choice of a landing method was inextricably tied to the size, weight, and shape of the Gemini spacecraft. In keeping with the initial plan of Gemini as a direct follow-up from Mercury (it was initially designated Marcury Mark II), the spacecraft was to be a larger, more sophisticated Mercury capsule built by the same contractor, McDonnell Aircraft. This essentially negated any chance of Gemini being an aerodynamically sound vehicle, but didn’t mean it couldn’t make a soft, controlled land landing. (Pictured is a scale comparison of the Mercury, Gemini, and Apollo spacecraft and launch vehicles. Mercury is the smallest of the three with Gemini as the intermediate. Apollo, clearly, dwarfs both.)

The list of possible landing methods was narrowed down to the two most promising designs involving controllable parachute-inspired designs – the parasail and the paraglider. While both methods were determined as roughly equivalent in weight, landing area requirements, speeds, and rate of descent, the paraglider had one key advantage over the parasail: it was significantly more manoeuvrable than the parasail. It could be flown like an airplane, is more controlled by the astronaut than by the wind, and is a design much preferred by the men who would fly it.

The paraglider was also expected to receive a positive public response. Its similarity to an airplane in its control and ability to land on a runway was a recognizable technological achievement. This was especially the case compared to the Soviet method of ejection. If NASA could be seen doing something better than the Soviets, the boon to public pride and support of the space program would be invaluable. Recall that this decision was being made in the early 1960s when the Soviet Space Program had consistently bested the Americans in space. Reclaiming some dominance in the space race was an appealing prospect.

The paraglider was ultimately chosen as the land landing system for the Gemini program. It was deemed the most likely to meet the program goal of a pilot-controlled pinpoint landing on land. Not to mention Gilruth’s previous interest in the design and the existing work on the system made it the simplest method to work into the physical Gemini spacecraft already on the drawing board.

The Rogallo wing wasn’t limited to the Gemini program; it was anticipated to be a long-term solution to the problem of land landings from space. Pending its successful incorporation into the Gemini program, the system was poised to be a fixture in spaceflight for decades to come, both within NASA was well as future military endeavours in space.

Not everyone supported the shift to pilot-controlled land landings. There were many within NASA who felt that if splashdowns weren’t broken they ought not be fixed. As such, splashdowns remained part of Gemini as a backup. In the even that the paraglider couldn’t be completed on schedule or the most problematic event of a malfunction during a mission, slashdowns were a tried and true method desirable in the event of an emergency.

So the two methods were developed for Gemini simultaneously, splashdowns taking a back seat to the new paraglider system. But for all the faith NASA had in its new landing system, it never flew. All the images of returns from space throughout Gemini as well as its successor Apollo depict splashdowns. The story of what went wrong, like the genesis of the Rogallo wing’s initial selection, is best told on its own.

 

Suggested Reading/Selected Sources

1. Milton Thompson with Curtis Peebles. Flying without Wings. Smithsonian Institution Press. 1999.

2. David Shayler. Gemini: Steps to the Moon. Springer Verlag. 2001.

3. Virgil I. “Gus” Grissom. Gemini: A Personal Account of Man’s Venture into Space. The Macmillan Company. 1969.

4. Hacker and Grimwood. On the Shoulders of Titans: A History of Project Gemini. Washington: NASA. 1977.

5. “The Gemini Program” – The John F. Kennedy Space Center. http://www-pao.ksc.nasa.gov/kscpao/history/gemini/gemini.htm. Revised March 10, 2004. [Accessed October 2, 2009].

6. Francis M. Rogallo. “Paraglider Recovery Systems”. NASA Archives, Washington D.C.

7. Jim Chamberlin “Draft on Gemini Land Landing Systems”. NASA Archives, Washington D.C.

Comments

  1. says

    vintage space rockets to the moon required a million people working together for the project and all designed by hand and computers only had 4k of memory with only a success rate of 80% which ment 20% didnt get home ..skeatesy

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