Project Manhigh

by Gregory P. Kennedy.
Greg Kennedy is the author of Touching Space.
The definitive history of Project Manhigh.

In the 1950s, a small band of Air Force scientists used balloons to carry live animals to the very edge of space. They performed this work out of the Aeromedical Field Laboratory (AMFL), which was located at Holloman Air Force Base near Alamogordo, New Mexico.

Lieutenant Colonel John Paul Stapp, MD, headed the AMFL. Major David G. Simons was the project officer for the balloon flights. Simons wanted to see what effects cosmic radiation had on living tissue. After several years of research and more than 80 flights, Stapp asked Simons if he thought he was ready to try a manned flight and if he would be willing to make that flight. Simons responded that he was, on both counts.

These flights were made with large balloons made from thin films of polyethylene plastic. Otto Winzen developed the plastic balloon under contract to the Office of Naval Research while he worked at General Mills. Winzen left General Mills in 1948 and started his own company, Winzen Research, Inc. (WRI.) Because of their light weight, these balloons, which the Navy named "Skyhook," could reach altitudes in excess of 100,000 feet.

Scientists soon began flying packets of photographic emulsion to capture cosmic radiation particles on Skyhook balloons. By 1948, researchers determined that 99% of cosmic radiation particles comprised hydrogen and helium nuclei. The remaining 1%, however, were made up of heavier atoms like carbon and iron. Traveling at tremendous velocities, the heavy particles were particularly troubling from a biological perspective.

Most of the early Air Force balloon flights were made from Holloman Air Force Base. Simons soon discovered that the specimens did not receive any appreciable radiation exposure. Because the earth's magnetic field deflects most cosmic radiation particles away from equatorial regions, the biological flights had to be conducted from northern latitudes to receive any significant exposure.

One factor affecting Simons' decision was that he quickly calculated building a capsule large enough to sustain a human pilot would be a relatively straightforward task. Life support capacity in the biological capsules, which comprised 27-inch diameter spheres, was expressed in terms of the smallest animal flown, which was a mouse. Simons had already flown capsules with life support capacities of 200 "mouse units." A human worked out to about 500 mouse units, so they only had to increase the life support capacity by a factor of two and a half.

Simons, Stapp, and Winzen agreed on an approach and forwarded the idea to the Air Research and Development Command (ARDC). At first the ARDC turned down the project because they did not feel cosmic radiation research warranted such an effort. Then, Simons justified the work as contributing to the design of a manned space vehicle, and it was approved. This became known as Project Manhigh. The goal of Manhigh was to place a pilot in a sealed capsule above 100,000 feet for a 24-hour flight. At such an altitude, the pilot would be above 99% of the atmosphere, and would be in the functional equivalent of an outer space environment.

The Manhigh capsule was eight feet high and three feet in diameter. Made from aluminum, the shell comprised three separate sections: the upper dome, turret and lower shell. Most of the major systems were suspended from the turret. Six portholes, including one the pilot could open, were built into the turret. A tubular aluminum frame attached to the outside of the lower shell supported the capsule in an upright position before launch. This structure also doubled as a shock-absorbing system for landing. Lead acid aircraft batteries mounted on the external frame powered the capsule's systems. Equipped with individual parachutes, these batteries (which weighed 50 pounds each) could be dropped as ballast when expended.

Manhigh needed an active thermal control system because it would remain aloft for more than 24 hours. Since the electronic equipment inside the cabin and the pilot himself produced heat, Winzen concluded no heating system was needed.
Rather, the problem became one of trying to cool the capsule. An elegantly simple system that relied on boiling water had been developed for the animal capsules some years earlier. As atmospheric pressure decreases, so does the boiling point of water. Manhigh carried a container of water that boiled when vented to the outside atmosphere. The steam carried excess cabin heat with it. The major disadvantage of this system was that it only worked at high altitudes. To keep the cabin (and pilot) cool prior to launch and during the initial ascent, a cap of dry ice was placed on top of the upper dome.

The pilot breathed a mixture of 60% oxygen, 20% nitrogen and 20% helium. Pure oxygen was rejected because of the fire hazard. Nitrogen, which normally comprises about two-thirds of the atmosphere at sea level, presented hazards of another sort. If there were a sudden decompression, nitrogen dissolved in the pilot's blood stream could bubble out, causing the "bends." Adding helium to the capsule atmosphere reduced the risks of fire and the bends. The pilot wore a standard Air Force MC-3 partial pressure suit in case of sudden pressure loss.

A 5-liter capacity bottle carried enough liquid oxygen to last 48 hours. There was an emergency oxygen supply in a cylinder under the pilot's seat and a bailout supply in a small bottle attached to the pilot's parachute harness. A three-step chemical "air-regeneration unit" removed carbon dioxide and water vapor from the cabin air. The three chemicals were packed in layers, in fabric bags. Air first passed through lithium chloride to remove moisture before it reached layers of lithium hydroxide, which absorbed carbon dioxide. The final step in the process was to circulate the air through magnesium perchlorate to remove any remaining moisture. A single regulator controlled pressure and oxygen content. In case the automatic system failed, the pilot had a manually operated valve that admitted a constant flow of oxygen.

The pilot had two communications systems. The primary system was a VHF transceiver for voice communications. If the voice system failed, he could use the telemetry transmitter to communicate via Morse code. Normally, this transmitter broadcast biotelemetry data from the pilot.

Manhigh began with six unmanned and animal flights to test launch techniques, life support system performance, balloon performance and recovery methods. Colonies of small animals in the capsule placed the same demands on the life support system as a human pilot.

While the engineers tested the capsule, the first two Manhigh pilots underwent training. Major Simons, as chief scientist, intended to make the ascent. Captain Joseph W. Kittinger, a pilot from Holloman's Flight Test Division, trained as his back up. Kittinger had flown for Colonel Stapp on earlier experiments and, after hearing of the project in 1955, volunteered.

Stapp and Simons listed the skills that could be necessary on a flight and structured the program accordingly. Their training included at least one parachute jump; balloon training leading to a balloonist's license; 24-hour claustrophobia tests in the capsule; a low-pressure, low temperature simulated flight in a test chamber; and a battery of physiological examinations.

Manhigh was never generously funded and, knowing the limited nature of the budget, Simons intended to perform the 24-hour scientific mission after the test flights. Stapp did not feel that was prudent. He told Simons: "Animal tests are fine, Dave, but I don't think that's enough. The animals did nothing up there but breathe, eat, and defecate. They didn't talk on the radio or shift around in a 180-pound mass or fidget in a pressure suit or try to grab scientific observations out of those saucer-sized portholes, or do any of the things you will have to do when you go up. To put the Manhigh system up now for a full-scale flight without at least one manned test flight first would be like trying to send a new fighter plane into combat without wringing the bugs out of it." Since the capsule was still untested in an actual manned flight, Stapp did not want to risk the project's chief scientist, so he directed that Kittinger pilot Manhigh I.

Kittinger took off at 6:23 a.m. on June 2, 1957. About two hours into the mission, he reached 97,000 feet and reported his oxygen tank was only half full. Since this was supposed to be a 12-hour test flight, ground controllers ordered him to descend immediately. Manhigh I landed in Indian Creek near Weaver, Minnesota, a little past noon. The oxygen tank, which was supposed to contain enough oxygen to last 48 hours, was empty because of an improperly installed pressure controller.

By the summer of 1957, the national debt reached its legal ceiling and federal agencies were instructed to curtail their spending. Within the Air Force, research programs were particularly hard hit. Kittinger's flight exhausted Manhigh's funds, so it looked like Simons would have to mothball the project and hope for additional funding the following year. Stapp wanted a full-scale simulation of the 24-hour flight in a test chamber at Wright Patterson Air Force Base before Simons left the ground to make sure there weren't any problems like the one that brought Manhigh I to an end. The test and flight would cost $14,000 more than was available. Then, Otto Winzen proposed that his company underwrite the test and flight. He felt the good will and publicity generated by the flight would be a worthwhile investment.

Major Simons piloted the second Manhigh flight on August 19 - 20, 1957. He climbed 101,516 feet above the Earth using a 3-million cubic foot balloon. Simons was the first person to see a sunset and a sunrise from the edge of space. During the night, a thunderstorm developed beneath him. At one point, the balloon cooled enough for him to descend into the upper fringes of the thunderhead! Dropping ballast, he rose to a safe altitude.



After dawn, the storm stalled and remained between his aerostat and the ground. In those early morning hours, carbon dioxide began to build up in the cabin and Simons had to breathe oxygen through his pressure suit. The storm finally cleared in the afternoon and Simons began the long journey back. He landed at 5:32 that evening. His flight had lasted 32 hours and 10 minutes.

Simons was immediately catapulted into the limelight. He appeared on the cover of the September 2, 1957, issue of Life magazine and his personal account of Manhigh II was the lead story. Manhigh II was hailed as an amazing adventure on the road to space. Just six weeks after Simons' flight, an even more stunning achievement overshadowed Manhigh. On October 4, 1957, the Soviet Union launched the world's first artificial satellite. Named Sputnik, the satellite circled the earth every 96 minutes. A month later, the Soviets launched a second Sputnik, this one carrying a dog!

American reaction to the Sputnik successes included the National Aeronautics and Space Act of 1958 that created the National Aeronautics and Space Administration (NASA) and the National Defense Education Act, which provided federal funding for science and mathematics education. As part of the Air Force response, Brigadier General Don Flickinger of the Air Research and Development Command (ARDC) told Simons to prepare for a third Manhigh flight. By that time, Stapp had been promoted and transferred to Wright Patterson Air Force Base as head of the Aero Medical Laboratory; Lieutenant Colonel Rufus Hessberg took his place at Holloman.

Winzen Research built a new capsule for Manhigh III that incorporated many changes. The air regeneration system was completely redesigned. Instead of having three separate chemicals to remove moisture and carbon dioxide from the cabin atmosphere, Manhigh III used a single chemical system. A blower circulated cabin air through a canister filled with potassium hydroxide, which absorbed both moisture and carbon dioxide.

Like its predecessor, Manhigh III was covered with Mylar, but it was painted white. Manhigh's designers believed this passive technique would keep the capsule cool and they removed the water core heat exchanger. Another major departure from previous Manhigh protocols was that this capsule was not test flown with animals; the first time it left the ground it carried a human pilot.

Selecting a pilot for the third flight proved problematical. Anticipating that Manhigh might serve as a template for future manned space missions, General Flickinger suggested that candidates be screened to meet the qualifications expected for future space pilots. The screening process included an interview to determine motivation and scientific background; a four-day medical evaluation at the Lovelace Clinic in Albuquerque, New Mexico; a 24-hour test to observe each candidate's response to confinement in the Manhigh capsule; a full day of tests by a clinical psychologist; a session in a soundproof, unlighted chamber; and stress testing. This latter battery included centrifuge runs, one hour in a "hot box" (155o F. and 85% humidity) and a "cold presser" test that comprised immersion of the subject's feet in ice water while his pulse and blood pressure were monitored. Despite the focus on space flight screening, each candidate still had to complete one parachute jump and balloon training like Kittinger and Simons.

Initially, Otto Winzen and one of the project officers from the AMFL were considered. Winzen was eliminated from consideration in June, so Captain Grover Schock was nominated for the flight. With the further elimination of the unnamed AMFL officer, Schock became primary pilot; Captain Harry Collins, an Air Force parachutist, became backup. First Lieutenant Clifton McClure also underwent the grueling series of physical and psychological tests for Manhigh and passed, so he was kept in the program.

In August 1958, Schock and Winzen were critically injured during a training flight. Collins became the primary pilot and McClure became his backup. By the time McClure finished his balloon training, Collins had also been eliminated due to high cholesterol levels, so the 25-year old Lieutenant was the primary pilot. McClure had a master's degree in ceramics engineering.

Time was critical for the flight because the ARDC instructed the AMFL to finish Manhigh as soon as possible. By the autumn of 1958, President Eisenhower had assigned piloted space flights to the brand new civilian space agency, so there were no compelling reasons for the Air Force to continue Manhigh. With the hardware already paid for, the ARDC allowed the program to proceed, as long as it could be concluded quickly.

McClure qualified for a balloonist's license on September 28. Project meteorologist Duke Gildenberg predicted there was only a negligible chance they would have satisfactory weather any time during the entire next month. Rather than risk having the ARDC cancel Manhigh III, Hessberg and Simons moved it to Holloman. New Mexico was too far south to gather any significant cosmic ray data, but the flight could still serve as a control to judge the effects of the other flights. It could also serve as a model for future space flights because McClure was to be guided in his observations by a panel of experts on the ground.

Early on the morning of October 7, McClure sat in the capsule, ready for flight. By the time launch preparations were finished, the morning winds had started. Just ten minutes before launch, the three-million cubic foot balloon began whipping around, finally careening into the ground. There was a gentle, almost imperceptible "pop" as the bag tore. Winzen had only manufactured two balloons to manned flight specifications for the project -- now only one was left.

Everyone agreed to try again the next day. That night, McClure boarded the capsule a little past midnight. Just like Kittinger and Simons, he had a personal parachute in the cabin. This parachute hung from the capsule support structure. With all the handling and jostling the parachute had received during the past few days, the closing pins worked themselves loose. About three hours after he boarded the capsule, McClure brushed against the parachute and it popped open "with a muffled flump." Finding his lap full of fabric, he faced a serious dilemma.

McClure did not know if the balloon had already been laid out for inflation. The balloons were so fragile they couldn't be repacked once they were unrolled. If they opened the capsule and had an Air Force Rigger repack the parachute, it would delay the flight for several hours by which time the winds would have picked up like the day before. Rather than risk aborting the mission by reporting the open parachute, he remained silent and repacked it inside the capsule.

It was difficult, tedious work in the three-foot diameter capsule, but McClure finally closed the parachute container. Pausing to examine his handiwork, he discovered he had inserted the pins backwards. Before repacking the canopy, he'd vowed that he'd only make the flight if it were properly packed. McClure pulled the ripcord and repeated the task. This time he secured the container properly. The process had been very taxing and he was perspiring heavily.

Normal flight preparations included placing a cap of dry ice on top of the capsule before launch to keep the pilot cool. On this day, someone forgot to bring the dry ice. During the previous day's launch attempt, McClure reported feeling cold, so the feeling was it probably wasn't necessary so preparations continued. Without the added cooling of the dry ice, he continued to perspire.

Potassium hydroxide reacts with moisture to produce heat, and McClure was perspiring so heavily he saturated the air that was blown through the regeneration unit. The unit soon began blowing hot, moist air into the cabin. Compounding the problem, without the water core cooling system that had been present in the earlier capsule, there was no way to dissipate the heat at altitude.

McClure took off at 6:51, about six hours after he boarded the capsule. As he climbed past 24,000 feet, he reported the temperature in the capsule was 89o Fahrenheit. At 55,000 feet, the cabin temperature gauge read 94o. Everyone agreed something was wrong with the gauge; the capsule temperature couldn't possibly be that high so the flight proceeded. About 10:00, he reached the ceiling altitude of 99,700 feet.

Around 1:00, it became evident that something was seriously wrong. McClure's speech was sluggish and his pulse rate was up to 140 beats per minute. There was no telemetry for the pilot's body temperature; he had to report that verbally to the ground. Asked about his temperature, McClure replied it was 101o. A half-hour later, it was up to 102.3o. Measuring the cabin temperature with a mercury thermometer, he reported it was 96o!

An hour later, McClure reported his temperature was 103.4o. Hessberg ordered him to descend immediately. By 3:00, McClure had only descended a few thousand feet and had not yet established a steady descent rate. His temperature was up to 104.1o. Another hour passed, by which time McClure had established a descent rate of 500 feet per minute but he was still at 87,000 feet.

Hessberg considered cutting the capsule away from the balloon and bringing it down with the parachute, but there was a strong chance it would land in the rugged San Andres Mountains. For the time being, Hessberg let McClure retain control of the descent, although his pulse was approaching 180 beats per minute. McClure began seeing shimmering green splotches, even when his eyes were closed.

During the descent, McClure dropped an instrument that jammed the foot switch that controlled his voice communications. Unable to reach it, McClure could no longer transmit to the ground. After that, the command group couldn't know for sure if McClure was even conscious, but the descent proceeded smoothly and his pulse rate remained steady, so they refrained from cutting the capsule away from the balloon.

A little past sunset, Manhigh III landed on a level area of desert only a few miles from the takeoff point. With perfect timing, McClure released the balloon just as the capsule touched down. The capsule remained upright, the only one of the three flights to do so. McClure released the upper dome and began to climb out on his own. His pulse rate was 180 beats per minute; his temperature an incredible 108.5o! Although most of the original scientific objectives for Manhigh III were unmet, the flight stands as a testament to the power of human motivation and will.

Consideration was briefly given to adapting the Manhigh capsule for space flight. This was the Army's Project Adam proposal. Adam would have used a Redstone missile to propel a modified Manhigh capsule 150 miles above the earth. Adam came from the Army Ballistic Missile Agency (ABMA) at Redstone Arsenal in Huntsville, Alabama. The concept emerged in late 1957, shortly after Simons' Manhigh II flight. The ABMA submitted a formal proposal to the Pentagon in April 1958.

Simons, an Air Force officer, even traveled to Redstone Arsenal to discuss the project. However, the Air Force officially decided not to support Adam because they feared it might divert resources from the X-15 program. Adam didn't survive long: the Pentagon rejected the idea in July 1958 when responsibility for manned space flight was given to NASA. In testimony before the Congressional House Space Committee NACA (one of NASA's predecessor agencies) Chairman Hugh Dryden compared "tossing a man up in the air and letting him come back... [to] ...the circus stunt of shooting a young lady from a cannon."

Winzen also submitted a proposal for a 5-day Manhigh IV flight, but it never progressed beyond the proposal stage. Manhigh IV would have used a 5-million cubic foot balloon and a larger capsule than the first missions. Again, NASA's effort, Project Mercury, made such a flight superfluous. Initial planning for Project Mercury called for a test flight of the capsule using a balloon, but NASA managers soon realized there were too many environmental conditions - namely launch, acceleration, weightlessness, and reentry - that would not be tested during a balloon flight. Therefore, the test was deleted from the schedule.

So, what was the impact of Project Manhigh on space flight? The Manhigh flights demonstrated the reliability of cabin life support systems. Overall, the systems performed as planned. The closest to a life support system failure occurred during the first Manhigh flight when the oxygen pressure controller was installed incorrectly. Physical and psychological screening procedures used for America's first space pilots were first used to select the Manhigh III pilot. Medical personnel who supported Manhigh also supported Project Mercury.

Finally, and perhaps most importantly, there was the knowledge that it was possible to build a sealed cabin with a life support system that could sustain a human pilot in an alien, inhospitable environment. This knowledge helped pave the way for subsequent space flights.

© Gregory Kennedy
This article may not be reproduced in whole or in part without written permission of the author and