Landing methods and the Gemini program are two of my favourite topics, and I’ve previously posted about landing methods in Gemini. The Mercury program demonstrated sufficient reason to move away from splashdowns, and the second generation Gemini manned spaceflight program gave NASA an opportunity to do so – it was the first to actively pursue a pilot-controlled land landing system. NASA reviewed multiple proposals before selecting the Rogallo paraglider wing. (Left, a model Gemini spacecraft with a Rogallo wing. 1963.)
Beginning with its initial development in 1961, the Rogallo wing had a long and interesting history within NASA. For the moment, I will limit myself to its inclusion in Gemini, putting the system’s research and development timeline against the Gemini program as a whole. This will begin to unravel why, in spite of NASA’s best efforts, all Gemini missions ended in splashdown.
The Mercury program had shown just how dangerous splashdowns could be. All six missions ended in either the Pacific or Atlantic Ocean, and two were nearly fatal to the astronaut. Scott Carpenter’s late retrofire and lack of control during his descent made his Aurora 7 capsule’s splashdown point nearly 250 miles downrange. He was left in the open ocean for three hours while recovery crews located and reached him. Gus Grissom’s splashdown was without incident, but once in the Atlantic the hatch on his Liberty Bell 7 capsule opened prematurely. Grissom escaped the capsule as water flooded in. He fought against the waves while the recovery helicopter struggled to save the waterlogged capsule. Liberty Bell 7 was lost but Grissom was eventually pulled from the Atlantic. He was wet and shaken but otherwise fine. (Pictured, Navy divers assist Mercury Astronaut Gordon Cooper in exiting his Faith 7 capsule. 1963.)
The method was also labour intensive. The Naval forces on hand to recover one Mercury astronaut were significant ranging from eight to twenty-seven ships per mission for the duration of the program. Additionally, the passive role of the astronaut during landing had been a point of contention. They had been fighting for full control over their spacecraft since the beginning of Mercury.
The move to a pilot-controlled landing on land was a desirable one all around.
The Rogallo paraglider had the potential to simplify landing operations for the fledgling space program. It also promised to give the astronaut full control during the descent and landing phases while at the same time negating the need for such extensive support forces. (Right, the Rogallo wing’s inventor and namesake, Francis Rogallo with his wife.)
But bringing astronaut-controlled landings into the Gemini program was slightly easier said than done. Originally designated as Mercury Mark II, the Gemini spacecraft was a larger version of Mercury mimicking it in shape and size. Like its predecessor, Gemini was a blunt body capsule with an ablative heat shield over its larger end. It was also inherently non-aerodynamic. The Rogallo wing had the difficult task of turning the blunt capsule into a glider.
The theory behind landing with the Rogallo wing is fairly simple. Gemini would reenter the atmosphere like the Mercury capsule – retrorockets would slow the spacecraft in orbit, beginning its fall to Earth. Its ablative heat shield would protect the astronaut inside from the heat generated during reentry. Once the spacecraft was safely into thicker atmosphere, the paraglider would deploy from one side of the spacecraft. As the wing unfolded and inflated, it would pull the spacecraft into such an orientation that the astronauts inside were sitting as though in an aircraft, facing out the front windows. Fully inflated, the wing was two-lobed sail design under which the spacecraft suspended by five wires. (Left, the proposed landing sequence for the Gemini spacecraft using the Rogallo wing.)
Controlling the mated capsule and paraglider necessitated an entirely new way of flying. The sail didn’t turn the spacecraft into a traditional aircraft so there were no ailerons or rudders for control. Because it flew in the atmosphere, ballistic controls like those used during orbit or the upper atmospheric portions of an X-15 flight were of no use. It also wasn’t quite a glider. The wing generated some lift, but not enough to work on its own.
The astronaut controlled the mated spacecraft and paraglider by manipulating the cables that connected the spacecraft to the sail. By changing the wing’s angle relative to the capsule it would generate lift. This would shift the mated configuration’s centre of gravity and change the path of the capsule’s fall by altering its angle and direction of descent. Continual changes to the angle of the wing built up momentum and greater range of movement of the descending spacecraft, enabling the astronaut to gain significant control over his landing. Gemini would land on small wheels deployed on the underside of the spacecraft (relative to the position of the paraglider) on a runway.
Contracts for the spacecraft and the paraglider wing were awarded to McDonnell Aircraft and North American Aviation (NAA) respectively in late 1961. The former was a beneficial arrangement. McDonnell was also building the Mercury capsule and had been developing a larger version that would become the basis for the Gemini spacecraft. With the preliminary development underway, it was simple for the contractor to include the capacity for the paraglider wing in at the earliest stages of Gemini’s construction. There would be no need to retroactively modify the spacecraft to incorporate the landing system.
Tests of the Rogallo wing began in January 1962, a month before John Glenn became the first American to orbit the Earth. Like with the Mercury capsule models years previously, the initial tests were intended to determine the optimal design configurations of the paraglider. Scale models of a Gemini spacecraft with a paraglider fixed to the top were dropped from helicopters. Various wing deployment methods were also tested in this preliminary stage. These drop tests allowed engineers, flight crews, and the astronauts to gain a sense of how the design actually behaved. Observing its natural fall was a great indicator of the system’s inherent stability and aerodynamic qualities. (Left, W. C. Sleeman, Jr. inspects a model of the paraglider before a 300 mph wind tunnel test. 1962.)
Models were also tested in wind tunnels at NASA’s Ames Research Laboratory. These tests yielded more measurable data on the paraglider’s performance. The amount of lift produced could be determined by measuring the speed of the air moving below and on top of the wing.
This initial battery of tests yielded an equal mix of successes and failures. The failures, however, were significant. Most problematic was the sail’s tendency to disintegrate in wind tunnel tests, suggesting that structurally it might not be a flight worthy design. But the major failures were overlooked, explained away as only occurring during tests that pushed the design to its limits or mimicked far more severe conditions than anything NASA would permit a manned spacecraft to land in. After all, the astronaut’s ability to avoid dangerous landing conditions was one of the motivators behind a pilot-controlled landing system.
The flaws revealed by these initial tests were not serious enough to kill the paraglider program altogether. The failures were fixable, and the successes weighed heavier. Following minor design changes, the system’s development was hastened and a successful paraglider landing was upgraded to a primary program objective.
The preliminary schedule for the Gemini program as written in mid-1962 included paraglider landings almost right away – the first unmanned Gemini flight would be recovered by parachute in September 1963, and the second unmanned flight landing by paraglider a month later. The manned missions followed a similar schedule. An entry dated May 24, 1962 in the official program schedule called for paraglider landings for each of the manned missions except the first, which would be recovered by parachute. (Pictured, a full-scale inflated Paraglider model. 1961.)
Success early in its development inspired great confidence in the paraglider system. But success proved fleeting as continued testing brought an increasing amount of failures.
The wing’s structural problems persisted. Further drop tests saw more sails fall apart and in some cases the backup parachute also failed. More than one test vehicle was lost to a crash landing. This delayed the program as subsequent tests had to get at the root of the problem before development continue.
Wing deployment tests were also proving problematic. The sail wasn’t deploying consistently, at times not opening fully and failing to inflate with enough time to produce sufficient lift for a soft, controlled landing. If the sail didn’t open at a high enough altitude, a successful landing would be impossible.
The mounting failures finally took their toll on the paraglider program. Only one year after paraglider landings had been worked into the official Gemini flight schedule, the method was downgraded. In May 1963, early manned Gemini missions were set to use parachute-assisted splashdowns, not just the first. Paraglider landings were delayed until the tenth mission of the program. This guaranteed the system’s very limited participation in the program. Since Gemini was never intended to be more than a bridge between Mercury and Apollo, delaying the paraglider’s use until the tenth mission meant at most only the last three missions would land using the system. (Left, a tow test of a 50-foot paraglider model. Barely visible against the light sky are the cables connecting the spacecraft to the glider and a tow line coming from off in the upper left of the image.)
The mounting problems also led to a contractual renegotiation between NASA and NAA. The revised contract in 1963 stipulated that NAA complete the development of the paraglider and deliver a working system to NASA. The wing-sail design was to be modified for optimal deployment and a test program was to be completed using both half- and full-scale tests. The new contract made no mention of either including the paraglider system into the Gemini spacecraft or of flying the system at all in any manned spaceflight program. At this point, the paraglider’s future inclusion in Gemini was increasingly unlikely, but the system on the whole was still deemed worth pursuing.
Compounding the problems surrounding the paraglider’s development was NAA’s conflict of interest with its other NASA contract – in 1962, NAA won the bid to build the Apollo command module, a much more important piece of hardware in the grand scheme of things. The company only had so many employees, and the majority of its resources were quickly diverted to Apollo as a priority.
Development of the Rogallo wing continued under the revised contract through 1964 with the ever-present mix of successes and failures, but the successes came too late. The first unmanned mission, Gemini 1, launched and splashed down in April 1964 and the first manned mission was scheduled within the year. There wasn’t time to work out the kinks and incorporate the paraglider system. Splashdowns at this point were a tried and true method, viable for Gemini as proved by the success of Gemini 1. If Apollo was going to meet Kennedy’s end of decade deadline, Gemini couldn’t wait for the glider. The moon was far more important in the short term than a land landing. (Pictured, the result of one crashed paraglider test flight.)
On February 20, 1964, NASA Associated Administrator George Mueller killed the Rogallo wing as far as the Gemini program was concerned. He announced to the Gemini Program Office that all twelve Gemini flights – two then-completed unmanned and ten scheduled manned missions – would end with splashdowns. As though holding out for some miracle, the Gemini quarterly report for the period ending in February 1964 still listed paraglider landings as the mode for the last three missions.
From that point on, the paraglider’s death was swift. In May 1964, NASA and NAA agreed to pursue the paraglider for flight test purposes only; there was again no mention of any manned flights. In June, Gemini Program Manager Charles Matthews removed the paraglider as a program requirement. The last mention of the paraglider in the official Gemini program history is a cursory remark from December of 1964, three months before the first manned mission, Gemini 3.
Multiple factors caused the paraglider’s removal from the Gemini program. Perpetual failures were at the heart of the matter. As Mercury and Gemini astronaut Gus Grissom wrote in his memoirs of the Gemini program, the theory of the paraglider refused to translate into practice. On paper the system seemed like a sure-fire way to restore control to the pilot during landing, but it never materialized. (Left, a model Gemini spacecraft with Rogallo wing.)
Each failed test necessitated further testing to determine the problem, which led to fatal scheduling delays. Another contributing factor is the tight time frame associated with the program. The looming lunar goal effectively made Gemini into a crash program like Mercury – it answered an immediate need through crude means, but it got the job done.
Although the paraglider was scrapped from Gemini in 1964, it didn’t disappear right away. Having spent significant time and money developing the system, NASA was determined to put the glider to good use. The Rogallo wing wasn’t put to rest until the mid-1970s. In the interim period, there was talk of using the method to land Apollo, and the US Air Force considered using the system in its military space ventures. The Rogallo paraglider’s story, as well as the stories of the men who built and tested it, will continue in future posts.
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.