AidSpace Blog

Inventing the Apollo Spaceflight Biomedical Sensors

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During the Mercury, Gemini, and Apollo missions, one of NASA’s concerns was the safety of its crews, something it monitored rigorously through the use of biomedical instrumentation. As initial flight planning commenced in 1959, biomedical equipment capable of transmitting from space did not exist. NASA quickly brought together medical staff and hardware engineers to develop biomedical technology. As they blasted off from Earth, the first American astronauts were wearing electrodes to collect electrocardiograms (ECGs, measuring the classic heartbeat waveform); a heated thermistor that detected breathing by cooling due to air movement in and out of the mouth; and, most unfortunately for them, a rectal probe that captured highly accurate body temperature readings. No wonder that astronauts, accustomed to self-sufficiency and relative isolation during their test pilot days, chafed at this literal and metaphorical intrusion.

Throughout the 1960s, NASA continued to tinker with its bioinstrumentation to find an ideal balance between obtaining accurate, important information and astronaut comfort. The assembly in the picture below is one of their early test models for the Apollo program. This object was featured in an earlier blog post on conservation, which you can find here. This time, I’d like to explore the function of these components.

biomedical equipment

The fully assembled test model for Apollo’s biomedical monitoring capabilities.

The most interesting variable to NASA’s medical division was cardiovascular function. Did the heart’s ventricles, normally ready to pump blood to the body every second, have trouble filling with blood in the weightlessness of space? Did fluids reach the lower extremities sufficiently without gravity? What about adaptations to space—werethey detrimental to an astronaut upon his return to Earth?

ECG electrodes were the first tool to gauge heart health. Readings from Mercury flights were often thwarted by movement, vibrations, and bumps. For Apollo, NASA contracted Spacelabs, Inc. to develop more reliable and accurate readings by use of a signal conditioner. Electrodes transmitted their raw signal via the orange wires to the two black conditioners on the left in this picture, which consisted of complex circuitry to identify and reject unwanted noise so the output was more representative of the astronaut’s state of being.

signal conditioners

The signal conditioners for the measurements coming from the ECG electrodes (the two left boxes), as well as signal conditioners for temperature and an unidentified sensor.

In addition to heart rhythm, NASA wanted to measure blood pressure. They initially introduced a semiautomatic sphygmomanometer (blood pressure cuff with pressure transducer and microphone) during Mercury and, for the most part, it remained similar for the Gemini and Apollo missions. The pressure cuff would slowly deflate, and the microphone would record pulse sounds to pinpoint the systolic (during heartbeats) and diastolic (in between heartbeats) blood pressures. This information was transferred to a signal conditioner, shown in the picture and diagram below. For this signal conditioner, NASA’s contractors designed a tiny pressure transducer (converting pressure to voltage), built a filter to precisely pick up noise at the systolic and diastolic blood pressures, and managed to make the entire signal conditioner small, lightweight, and low on power usage.

microphone conditioner and chart

The microphone (top) and its unique signal conditioner specially engineered to read in both sound and pressure. The diagram is a representation of its internal mechanisms.

Beyond the heart, NASA wanted to keep tabs on astronaut breathing. Because the thermistor of Mercury days (a resistor that changed its resistance at different temperatures) did not reliably track respiration, NASA moved to an impedance pneumograph technique. At the time, impedance pneumography was a little known technique, yet through NASA’s research and development it was eventually found to be a very successful tool, even in a demanding flight environment. When a constant electric current is introduced into a human’s chest tissues, the fat, muscle, lungs, air, and fluid all create a natural impedance (or opposition to current flow), which can be measured via voltage. As the subject draws in air and stretches the body tissues, the impedance changes which subsequently changes the voltage drop. NASA stuck an electrode close to the astronauts’ sixth ribs (the optimal spot) and used results from a Baylor University study to correlate impedance to the amount of air in lungs. Spacelabs, Inc. built another signal conditioner for the impedance sensor shown below. The end result was so good that flight surgeons in Houston watched every deep breath as astronauts hopped onto the surface of the Moon or headed out the hatch for a deep space extravehicular activity or EVA.

The impedance pneumograph signal conditioner.

The impedance pneumograph signal conditioner.

Finally, NASA came to understand that temperature monitoring via the rectum was not optimal for astronauts on long journeys to the Moon and back. They replaced it with an oral sensor for the Gemini and Apollo flights shown below, built with a Velcro patch for attachment inside the astronaut’s helmet. The black neoprene sleeve on the probe was simply for traction, as the probe itself, coated in Teflon, proved to be slippery and difficult to hold in the mouth. Intermittently, astronauts would place the sensor beneath their tongue for up to five minutes to produce a reading.

The oral temperature sensor, reminiscent of oral thermometers back on Earth.

The oral temperature sensor, reminiscent of oral thermometers back on Earth.

While far more complex biomedical information has been collected on astronauts since the 1960s, the instruments seen here were the pioneering designs, compiling information about the influence of weightlessness on essential bodily functions. The astronauts themselves may have been irritated with NASA’s meticulous cataloging of their body’s performance, but it came in handy in many instances, like when Gene Cernan physically struggled to perform his EVA tasks during Gemini IX-A, and when Dave Scott and Jim Irwin had heart irregularities on the surface of the Moon during Apollo 15. Biomedical monitoring allowed NASA to identify problems in real time and devise solutions for current and future astronauts, and today we continue to probe human health in space so that one day we might prepare for the challenges of sending astronauts to Mars and other celestial targets.

John Miller is a biomedical artifacts intern in the Space History department at the National Air and Space Museum. He is working towards his M.S. degree in Biomedical Engineering at the University of Virginia.

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The First Pictures from the Moon’s Surface

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Half a century ago, in February and June 1966, robotic spacecraft first landed on the Moon. I vividly remember those events from my days as a 14-year-old space buff. On February 3, the Soviet Union’s Luna 9 thumped down on the vast lava plain known as Oceanus Procellarum (Ocean of Storms), after a number of failed attempts. A Soviet stamp shows its landing configuration, which used air bags to cushion its fall. On the right is the first picture transmitted, from the turret camera in the cylinder on top.


The Soviet Union 1966 CPA 3317 stamp feature the first images of the Moon’s surface taken by the Luna 9 spacecraft.

This image was intercepted by the Jodrell Bank observatory in England, which beat the Soviets to releasing it. The quality in this version was less than ideal, but it was the one that made the newspapers like my hometown Calgary Herald.


The first image of the Moon’s surface intercepted and released by the Jodrell Bank observatory in England.

Luna 9, which was only powered by batteries, lasted three days, enough to transmit a panorama from very close to the surface

The United States’ first successful landing on the Moon came on June 2, when NASA’s Surveyor 1 touched down on another part of Oceanus Procellarum, which is the large dark area on the right side of the full Moon. That landing, I remember especially well, as it was carried live on TV from the Jet Propulsion Laboratory in Pasadena, California. It unfolded around midnight, Calgary time, and no one knew whether it would work or not. One of the first pictures Surveyor 1 took was of its foot pad.

The first picture captured by Surveyor 1 of its foot pad.

The first picture captured by Surveyor 1 of its foot pad.

This image, along with data transmitted from strain gauges in the three landing legs, gave valuable information to NASA about the bearing strength of the lunar surface, vital for planning the Apollo missions that were to follow.

Surveyor was a more sophisticated, solar-powered spacecraft. The Museum has a test vehicle made to look like the second successful lander, Surveyor 3. The solar panel is on top and the flat panel for the main antenna to transmit to Earth is behind it. The TV camera is located in the white cylinder with the oval mirror under the solar panel. The Surveyor 3 had a scoop (lower right) for testing the soil’s characteristics, but it was not on Surveyor 1.

Surveyor 3

The Museum’s test vehicle made to look like the second successful lander, Surveyor 3.

Surveyor 1 shut down during the 14-day lunar night but revived and transmitted pictures until July 14. Even after that it was able to send back engineering data during lunar days until January 1967. Its panoramas have been processed more recently by Philip J. Stooke of the University of Western Ontario.

Moon panoramas

Panoramas captured by Surveyor 1 and recently published by Philip J. Stooke of the University of Western Ontario.

Those were exciting days for space enthusiasts and for the general public. We were witnessing the first pictures taken from the surface of another world. That same summer, spacecraft also went into orbit around the Moon for the first time. Luna 10 and Lunar Orbiter 1 transmitted many more images, as did their successors. Three years later, humans walked on the Moon, helped in no small part by their robotic precursors.

Michael J. Neufeld is a senior curator in the Space History Department of the National Air and Space Museum. He is the lead curator for Destination Moon, a new exhibition on lunar exploration that is scheduled to open in late 2020.

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Stories from Mother Tusch’s Birthday Book

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In a recent blog post, Kathleen Hanser told the story of the “Shrine of the Air” in Berkeley, California, and highlighted various artifacts from “Mother” Tusch’s house that became a part of our collections. The paper documents from Tusch’s house can be found in the National Air and Space Museum Archives as part of the Mary E. “Mother” Tusch Collection (Acc. No. XXXX-0128).

Famous and not so famous visitors to Tusch’s bungalow usually signed her register. One page from March and April 1946 bears the signatures of General Henry H. “Hap” Arnold; Frank T. Coffyn, early aviator and student of the Wright brothers; Robert G. Sproul, president of the University of California; and E.C. Koerper, a captain in the Air Reserve, who visited with Sproul. The registers were highly valued. One year, the register was stolen on August 9, but had been returned on September 30, a theft worthy of local newspaper coverage.

scan of Tusch's register

Page of Register 5 (1940-1949), compiled by Mary E. “Mother” Tusch.  Signatures include General Henry H. “Hap” Arnold, Frank T. Coffyn, Robert G. Sproul, and E.C. Koerper. NASM 9A12046-046

A unique item in the Mother Tusch Collection is her birthday book. The book itself was given to Tusch by Sergeant Hugh J. Williams in 1918.  Williams was a member of the medical department who completed the School of Military Aeronautics on August 5, 1918. For years, Tusch recorded the birthdays of the men (and women) who visited her.

dedication page

Dedication Page of Mother Tusch’s Birthday Book. “Gift of Sergeant Hugh J. Williams, Med. Dept., Completed about August 5, 1918.” NASM-9A12047-001-002

The very first entry in the book on January 1st is “Father Time – A plodder but he gets there.” George Washington is featured on February 22, “The Father of His Country,” and Tusch’s daughters Dorothy Belle, “Fairy of the Household,” and Irene can be found on March 18 and July 10, respectively. Although every person in the book has his or her own background story, sometimes Tusch herself provided a little history on the names. For example, on November 27, next to John W. Benton, Tusch noted: “Killed in Goodwill trip to South America.”

November entries in Tusch's birthday book.

Mother Tusch’s Birthday Book, November 26 and November 27. NASM-9A12047-337-338

First Lt. John W. Benton was a pilot in the United States Army Air Corps. In 1926, the Army Air Corps and State Department planned a Pan-American goodwill mission to Mexico, Central and South America, and the West Indies. The goal was to showcase American-made aircraft and engines and highlight air travel as a possibility in regions that did not have many transportation options. Five Loening OA-1A amphibian aircraft were chosen for the trip and named the New York, the San Antonio, the San Francisco, the Detroit, and the St. Louis.

landscape portrait

Five Loening OA-1A aircraft with 10 pilots pose at Kelly Field, San Antonio, Texas, on December 21, 1926, before leaving on a four month, 35405.568 kilometer (22,000 mile) Pan-American Goodwill Flight. Left to Right: San Francisco: Capt. A.B. McDaniel, pilot; 1st Lt. Charles Mck. Robinson, copilot. Detroit: Capt. C.F. Woolsey, pilot; 1st Lt. John W. Benton, copilot. Flagship New York: Maj. Herbert A. Dargue, pilot and commander of the flight; 1st Lt. Ennis Whitehead, copilot. St. Louis: 1st Lt. Bernard S. Thompson, pilot; 1st Lt. L.D. Weddington, copilot. San Francisco: Capt. Ira C. Eaker, pilot; 1st Lt. Muir S. Fairchild, copilot. NASM A-45942

On February 29, 1927, the New York and Detroit collided in mid-air as they were landing at the Argentine Air Service Field at Palomar, Buenos Aires, Argentina. The crash destroyed both aircraft and killed the crew of the Detroit, pilot Capt. C.F. Woolsey and Benton. Both men were awarded the Distinguished Flying Cross posthumously.


Lieutenant John W. Benton, United States Army Air Service, seated, in uniform, wearing hat; circa mid 1920s. NASM 9A10437

The other aircraft completed the flight and returned to Bolling Field, Washington, DC, where they were congratulated by President Calvin Coolidge. The Loening OA-1A San Francisco is on display at the Steven F. Udvar-Hazy Center in Chantilly, Virginia.

John W. Benton is just one of many possible stories that can be told from Mother Tusch’s birthday book. She even had a special story celebrating her birthday, December 26: “Mother Tusch—(the best Xmas present of them all).”

Elizabeth C. Borja is an archivist in the Museum’s Archives Department.  Last Mothers’ Day, she celebrated the mothers of famous aviators.

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Obscure Objects: Mary E. “Mother” Tusch Plaque

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“God bless you,” was the way in which “Mother” Tusch said farewell to pilots who visited her at her Berkeley, California cottage from 1915 to 1950, so it is fitting that the phrase is engraved on this plaque found among her vast collection of aviation memorabilia.

bronze plaque

This bronze commemorative plaque measures 50.8 x 1.3 x 20.3 cm (20 x 1/2 x 8 in.) and shows Mary Elizabeth “Mother” Tusch on the right and her husband, Cary, on left, with torches depicted on each side. In raised letters in the middle it says, “Mother of Aviators,” and below that, “God Bless You.”

This bronze commemorative plaque measures 50.8 x 1.3 x 20.3 cm (20 x 1/2 x 8 in.) and shows Mary Elizabeth “Mother” Tusch on the right and her husband, Cary, on left, with torches depicted on each side. In raised letters in the middle it says, “Mother of Aviators,” and below that, “God Bless You.”

The plaque declares Mary to be the “Mother of Aviators,” and that is no exaggeration. Mary Tusch welcomed hundreds, if not thousands, of aviators — some famous, some not — into her bungalow across the street from the School of Military Aeronautics at the University of California, Berkeley. She served as a mother figure to them, many of whom were far from home and would soon be going to war, and she called them her “boys.” Soon she became known to all as Mother Tusch.

Mother Tusch became an avid collector of aviation objects, and those who visited her brought mementos from their travels and flying exploits to add to her collection. Over the years, her little house was filled wall-to-wall with flight-related items such as photos, scrapbooks, autographs, newspaper clippings, posters, maps, log books, and correspondence, along with objects such as insignias, medals, plaques, goggles, helmets, coats, propellers, and art made out of shell casings. The house became known as “The Hangar, Shrine of the Air.”


One section of the inside of Mother Tusch’s house known as the “Shrine of the Air.” You can see the pilots’ signatures on the wallpaper at the top. Image: National Air and Space Museum, NASM 00177743

Mother Tusch came to know many famous aviators, including Charles Lindbergh, Eddie Rickenbacker, Richard Byrd, Amelia Earhart, Jimmy Doolittle, Roscoe Turner, and Billy Mitchell. She often invited visitors to sign her wallpaper, which featured silhouettes of airplanes and became literally covered in signatures, including those of her most notable friends.

Some of the most interesting items in her collection included the fur and cloth cap worn by Adm. Richard Byrd on an Antarctic expedition; the protective helmet from the early days of Henry “Hap” Arnold’s flying career, ca. 1910-1911 (he later became World War II Commander of the Army Air Forces); and a Royal Air Force flying coat purported to have been worn by Edward, Prince of Wales, in World War I.

informal portrait

Informal photo of Mary E. “Mother” Tusch sitting on a couch at her home in Berkeley, California circa 1949. She is displaying an autographed photo of General William E. “Billy” Mitchell. Image: National Air and Space Museum, NASM A-46813-A

In 1950, when Mother Tusch’s health deteriorated to the point where she had to move to Washington, DC to live with her daughter, Irene, she donated the entire collection, including the carefully peeled-off wallpaper, to the Smithsonian’s National Air Museum, the precursor to the National Air and Space Museum. The donation was due, in part, to family ties. Irene was married to Air Museum curator Paul Garber. At the time of the donation, Gen. Hap Arnold described it as, “the finest … in the world of historic air-related objects.” Parts of the collection were placed on display in one of the Air Museum’s two buildings — the Arts & Industries building or the Aviation building — shortly after the donation.

Mother Tusch at the Smithsonian

Maj. Gen. William E. Hall, Mother Tusch, Irene Tusch Garber, and Paul Garber at the opening of the Smithsonian’s display of Tusch’s collection of aviation mementos, 1950. Image: National Air and Space Museum, NASM 2003-25364

Mother Tusch was an honorary member of the Women Flyers of America, The Veterans of Foreign Wars, The National Aeronautic Association, the Exchange Club, and the League of American Penwomen.

She died in 1960 at the age of 85. Her husband, Cary, a civil engineer, had died in 1928. Their ashes are buried side-by-side in the Urn Garden of the Sunset View Cemetery in Contra Costa County, California. Their gravemarker is a duplicate of the plaque shown above.

Kathleen Hanser is a writer-editor in the Office of Communications at the National Air and Space Museum

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Adjusting Our Atomic Clock for the Leap Second

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Our exhibition Time and Navigation features an atomic clock that will keep an accurate time within a tiny fraction of a second for the foreseeable future (see my earlier post to learn how atomic clocks work and how we installed ours into the exhibition). Except, of course, when we need to account for a leap second.

 What’s a Leap Second?
In the past, time was measured using the rotation of the Earth. With atomic clocks, we learned that the length of a day changes by a second here and there. To take this into account, in 1972 the International Telecommunications Union adopted “leap seconds.” A leap second is added whenever the Earth’s rotation gets out of sync compared to the international time reference measured with atomic clocks. There is a discussion about leap seconds and if they will continue to be added, but that is another story. For our purposes, we just needed to keep our atomic clock in sync with the world’s time when the last leap second was added in June 2015.

Adding the Leap Second
Because our atomic clock is not connected to outside data sources, we had to add the leap second manually. This required opening the front of the exhibit case and typing a series of commands on the keypad a few days before the leap second would occur. We told both the frequency standard and the time code generator to add the leap second on the last day of June. We also successfully tested the cable connection in the back of the atomic clock. From now on, we’ll use that to update the clock for future leap seconds.

Leap seconds are always added at midnight Coordinated Universal Time (UTC). For us, that was 8:00 pm in Washington, DC. With our commands entered earlier, I waited around in the Time and Navigation gallery to see what would happen as the clock struck 8:00. The leap second went off without a hitch.

It was interesting to watch the displays.

UTC on the cesium clock displayed these seconds:


Above the clock, local time from the time code generator displayed:


This video shows the time displays 5 seconds before and after 8:00 pm. The elapsed time was 11 seconds instead of 10 because of the leap second.

Please come visit the Time and Navigation exhibition to see the working atomic clock. You can set your watch to the correct local time displayed in the upper part of the case.

Andrew Johnston was a research associate in our Center for Earth and Planetary Studies. He is now the Vice President of Astronomy & Collections at the Adler Planetarium in Chicago.

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