The Deep Space EVA That Shouldn’t Have Happened: Apollo 15, Jim Irwin, and Medical Transparency at NASA, 1971

Nearly 51 years after the mission ended, Apollo 15 still stirs up questions.

S71–43428 (8 Aug. 1971) — — The three crewmen, of the highly successful Apollo 15 lunar landing mission, receive a warm welcome home at Ellington Air Force Base (EAFB), Houston, after an eight-hour flight aboard a U.S. Air Force C-141 jet aircraft from Hawaii. Left to right, are astronauts David R. Scott, commander; Alfred M. Worden, command module pilot; and James B. Irwin, lunar module pilot. Apollo 15 splashdown in the mid-Pacific at 3:45 p.m. (CDT), Aug. 7, 1971, some 330 miles north of Honolulu. The C-141 landed at EAFB at 9 p.m. (CDT), Sunday, Aug. 8, 1971. Members of the astronauts’ families identifiable in the picture are, left to right, Scott’s daughter, Tracy; Worden’s father, Merrill Worden; Worden’s daughter, Merrill; and Irwin’s two daughters, Joy, and Jill. NASA photo.

The day was August 5, 1971, and astronaut Alfred M. Worden’s place in the history books was already assured. He was in the process of becoming the first-ever astronaut to perform a trans-lunar EVA, with full sight of both the Moon and the Earth. If you listen to the audio from this EVA, you’ll find that Worden was wholly task-oriented and he took little time to enjoy the miraculous sight of floating between two separate worlds for 39 minutes. While Worden couldn’t capture this moment on film, artist Pierre Mion famously immortalized it utilizing acrylic paint on canvas.

S71–39614 (July 1971) — — An artist’s concept of the Apollo 15 Command and Service Modules (CSM), showing two crewmembers performing a new-to-Apollo extravehicular activity (EVA). The figure at left represents astronaut Alfred M. Worden, command module pilot, connected by an umbilical tether to the CM, at right, where a figure representing astronaut James B. Irwin, lunar module pilot, stands at the open CM hatch. Worden is working with the panoramic camera in the Scientific Instrument Module (SIM). Behind Irwin is the 16mm data acquisition camera. Artwork by North American Rockwell.

From Worden’s 2011 autobiography, Falling to Earth, written with Francis French:

It was time to remove the mapping camera film cassette and bring that back inside, too. This time the cover didn’t cooperate, and I had to twist and pull hard three or four times before it came away. But after that, it was simple. I pulled the mapping camera film out and it floated back over to [lunar module pilot Jim Irwin, who was standing inside the hatch of command module Endeavour], who grabbed it and unhooked the tether from me.

As we did this, I saw one of the most amazing sights of my life. “Jim, you look absolutely fantastic against that moon back there.” I exclaimed. “That is really a most unbelievable, remarkable thing!”

Jim was perfectly framed by the enormous moon right behind him. It looked as big as the spacecraft, and was dramatically lit by the sun, emphasizing the rugged craters. I could even see myself, floating in space, reflected in Jim’s visor. It could have been the most famous photo in the space program, if I’d been allowed to take a camera out of the spacecraft.

S71–43202 (5 Aug. 1971) — — Astronaut Alfred M. Worden, command module pilot of the Apollo 15 lunar landing mission, floats in space outside the spacecraft during his trans-Earth extravehicular activity (EVA). This photograph was taken from a frame of motion picture film exposed by the 16mm Maurer camera mounted in the hatch of the Command Module (CM). During his EVA, Worden made an inspection of the Service Module’s (SM) Scientific Instrument Module (SIM) bay and retrieved the film cassettes from the Panoramic Camera and the Mapping Camera. The SIM bay holds eight orbital science experiments. The EVA occurred when the spacecraft was homeward bound approximately 171,000 nautical miles from Earth. NASA photo.

Later, Worden realized he could see both the entire Earth and the entire Moon simply by turning his head; in his words, “In all of human history, no one had been able to see what I could just by turning my head. It was incredible.

Despite the profound impact this moment undoubtedly had on Worden, in later years he came to question the rationale of conducting this EVA at all, as historic as it was and continues to be. In fact, he considered if it had played a part, no matter how infinitesimal, in the early death of the man who stood in the hatch of Endeavour that day. This is the story of how astronaut Jim Irwin risked everything to ensure Apollo 15 was a success, and how his crewmates later regretted not asking Mission Control — and him — more questions.


Rewind to three days before Worden made his EVA, as lunar module Falcon — named after the U.S. Air Force Academy’s mascot, as Apollo 15 was an all Air Force crew — rendezvoused with Endeavour after a seemingly successful four days at the base of the Apennine Mountains near Hadley Rille. Upon hatch opening, mission commander David R. Scott was apparently feeling spry enough to start an argument with Worden about playing the Air Force’s anthem on cassette during Falcon’s liftoff; Worden later wrote in Falling to Earth, “Dave and Jim didn’t seem weary to me, but it was hard to tell when we all had so much to do and were zipping around getting it done.” Worden added, “I put Dave’s slight ill humor down to his annoyance with me over the tune.”

There was more at play than just a slight misunderstanding over how much music the command module pilot should’ve (or shouldn’t have) played upon Falcon’s liftoff. Worden continued:

But then we heard a familiar, gruff voice over the radio, which only got in the loop when there was something important. “This is Deke [Slayton, chief astronaut],” the voice growled to Jim. “I’d like to have you and Dave, at least, take a Seconal here before you go to sleep so you can really power down for the night. You guys need it. It’s up to Al whether he wants one or not.”

“KENNEDY SPACE CENTER, FLA. — Apollo 15 Lunar Module Pilot James B. Irwin will be making his first space flight when he is launched to the Moon with astronauts David R. Scott and Alfred M. Worden. Irwin and Scott will conduct three traverses of the Moon’s Hadley-Apennine region while Worden maintains the command module in lunar orbit and conducts experiments. They will be launched to the Moon no earlier than July 26, 1971.” NASA photo.

Worden reported that Scott’s reaction was to “immediately [look] puzzled.” First, no reason was given why only Scott and Irwin would need to take a Seconal — a sedative — and Worden was not required to. Second, the crew was still busy performing experiments and stowing equipment. Remember, Endeavour would stay in lunar orbit for another day after Scott and Irwin had departed.

Commander Scott began to believe, at the same time, that Mission Control’s decision to sedate him and Irwin arose from what he characterized as a “slight delay in jettisoning [Falcon]” which led the ground controllers to give the crew “confusing and incorrect data immediately after the separation…Had we performed the CSM-LM separation maneuver as they originally calculated, we would very likely have made physical contact again with the LM, which we could see out of the window right ahead of us.” Here’s Scott’s account of this time in his joint memoir written with cosmonaut Alexei Leonov, Two Sides of the Moon: Our Story of the Cold War Space Race:

…As Jim and I had gone for nearly twenty hours without sleep by this stage, and had not eaten for eight hours, Mission Control seemed to think that we, not they, had got confused. They even suggested that Jim and I take a Seconal tablet that night to help us with sleep…

I was amazed at the suggestion and quickly dismissed it, assuming it had come from one of the NASA doctors monitoring our progress. They were always over-cautious as far as we astronauts were concerned. To my mind, though I did not say so at the time, taking a sleeping pill without good reason was ridiculous, given the extreme demands and level of alertness required of us in case of an emergency. Though physically tired, Jim and I were elated at how well our stay on the Moon had gone. We were relaxed and ready to sleep without pharmaceutical assistance.

For the aforementioned reasons, Scott made the command decision to decide against any of the crew taking Seconal. Scott reported that the following night, ground controllers again suggested that Irwin — only Irwin — take a sleeping pill, which the lunar module pilot refused; Mission Control’s insistence that only part of the crew take a sedative prior to a rest period further confused Scott.

Here’s Irwin’s account of what happened shortly following Falcon’s jettisoning, from his 1973 memoir To Rule the Night:

All of the sudden, for the first time in the flight, I was really tired.

I told Al and Dave, “Just let me lie here for a little bit. I am physically exhausted.” I lay down for about five or ten minutes as we were getting ready to take off our suits and prepare for bed. About that time, we got an unexpected call from Deke Slayton.

“You guys have had a hard day,” Deke said. “I suggest you all take a sleeping pill this evening.”

“We hear you, Deke,” I said, laughing. “We have had a busy day.” I thought he was joking, too.

AS15–92–12424 (31 July-2 Aug. 1971) — — Astronaut James B. Irwin, lunar module pilot, uses a scoop in making a trench in the lunar soil during Apollo 15 extravehicular activity (EVA) on the moon. Mount Hadley, which rises approximately 14,765 feet (about 4,500 meters) above the plain, is in the background. Its base is some 14 kilometers (about 8.4 miles) away. The gnomon is at left. While astronauts Irwin, and David R. Scott, commander, descended in the Lunar Module (LM) to explore the moon, astronaut Alfred M. Worden, command module pilot, remained with the Command and Service Modules (CSM) in lunar orbit. NASA photo.

While Irwin’s account of events runs contrary to Worden’s and Scott’s — they both claimed only Scott and Irwin were ordered to take a Seconal pill — all three crewmembers would later discover that Scott and Irwin had shown irregularities in their heart rhythms during their lunar EVAs. In Irwin’s words, “the heart gets confused…It often is caused by severe fatigue.” Simply put, it is probable that Irwin had been in cardiac distress on the lunar surface, and he — and his two fellow crewmates — had no idea, and subsequently were not informed of what had happened and what was continuing to happen to him until well after it was too late: after the crew had arrived home on August 7, 1971.


Afterward, Irwin and Scott received nine hours of sleep, and according to Irwin, he “felt normal despite my heart problem.” But Irwin’s troubles were far from over. A paper written by William J. Rowe published in January 13, 1998’s issue of Circulation further explored and explained what had happened to Irwin (and to a lesser extent, Scott) at Hadley Rille:

In 1971 on the Apollo 15 lunar mission, astronauts Irwin and Scott both experienced severe pain and edema of the fingertips. In addition, the mission was considered an “anomaly” since it was the first during any space mission distinguished by significant arrhythmias, more severe in Irwin’s case with a brief loss of consciousness during an episode of bigeminy after return to the command module. Twenty-one months later, Irwin experienced a myocardial infarction. It is conceivable that Irwin’s infarct was not coincidental but was at least partially triggered by endothelial injuries resulting from the Apollo 15 mission.

In the presence of microgravity, there is invariably a shift of fluid to the upper part of the body. But in addition on the Apollo 15 mission, there was a malfunction of the Insuit water devices, resulting in water deprivation, particularly in Irwin’s case during the three extravehicular activities (EVAs) of up to 7 hours each, whereas Scott’s Insuit apparatus functioned partially. Irwin, sweating profusely and extremely thirsty during the EVAs, lost 5% of his weight compared with his mean pre-flight weight (from 74.3 to 70.8 kg), whereas Scott lost about half that much (from 81.1 to 78.9 kg).

Before the Apollo 15 mission, there was a predisposition for a significant magnesium ion deficit, which may persist for several months, since training occurred “in intense summer heat.” This deficit would be compounded by a magnesium deficit secondary to skeletal muscle atrophy resulting from even this brief space mission (12 days). This conceivably could predispose to the serious arrhythmias and potassium deficits, potential catecholamine elevations with enhanced thrombus formation, and potential endothelial injuries of both peripheral and coronary vessels.

The aforementioned report that Irwin lost consciousness upon his return to Endeavour was not mentioned by all three Apollo 15 crewmembers. Rowe has also mentioned in separate presentations that Irwin had preexisting bouts of high blood pressure, which is a known risk factor for heart disease; however, it is not known how high it was, or if it was controlled.

David R. Scott speaks to the crew of the USS Okinawa after Apollo 15’s splashdown on August 7, 1971. His bruised fingernails are visible. Photo credit: The Project Apollo Archive.

It also bears mentioning that the damage to Scott’s hands was visible upon the crew’s return in August, and could be seen during post-flight press conferences on the recovery ship USS Okinawa and at the Manned Spacecraft Center in Houston; his fingertips were swollen, and his fingernails were severely bruised. Unrelated to any heart symptoms, according to post-flight biomedical evaluations and Two Sides of the Moon Scott also reported suffering a muscular/ligament strain to his right shoulder. However, Scott wouldn’t experience what Irwin did less than two years following the mission: a heart attack.

1971 AP Wire photo. Again, bruising on Scott’s fingernails is visible.

Immediately following splashdown, according to Andrew Chaikin’s A Man on the Moon: The Voyages of the Apollo Astronauts, Irwin knew all too well that he “wasn’t quite right.” Chaikin wrote, “He was still having difficulty adjusting to the pull of gravity, including some bouts of dizziness. He wasn’t doing very well on the stress tests in the medical physicals.” Around this period, NASA’s cadre of doctors informed Irwin and Scott about the heart issues they’d both experienced during their lunar EVAs. Chaikin explained why the two had suffered such issues:

During practice sessions for the moonwalks, Scott and Irwin had spent hours working in space suits in intense summer heat. To replenish lost fluids, they drank large amounts of an electrolyte solution, which tended to leach potassium from their systems. As a result, the doctors would conclude, they left earth with a potassium deficiency that was exacerbated by the stress of the mission, causing their subsequent heart irregularities. Irwin hoped that soon he would be back to normal.

In April 1973, shortly after retiring from the U.S. Air Force and NASA, Irwin was whisked to an intensive care unit after suffering his first heart attack while playing handball in Denver, Colorado. This event only proved to mark the beginning of the cardiac problems that would end Irwin’s life less than 20 years later.


Why was the Apollo 15 crew not informed about the heart irregularities during the lunar EVAs, or at least when Scott and Irwin returned to Endeavour? There’s the infamous story retold by Chris Kraft in his book Flight: My Life in Mission Control, which states that flight surgeon Dr. Charles Berry came to the conclusion that Irwin, if he was having a heart attack, was essentially in a “type” of intensive care unit, as he was breathing 100% oxygen being continuously monitored in a microgravity environment. That doesn’t answer, however, why Scott and Worden weren’t informed about his condition. Should Worden have performed the deep space EVA with Irwin assisting by standing up in Endeavour’s hatch? Here’s what Worden wrote in The Light of Earth:

One thing I’ve never understood — with Jim in the condition he was in, why did they give us the okay for me to do a space walk on the way back to Earth? I suspect that he had ingested enough liquid by then to get his potassium level back up to where his heart rate was okay. I was appalled when I found out later that they’d allowed him to get back in his pressure suit and float in the open hatch with a weakened heart. I guess mission control made a judgment call. They decided to take the risk that Jim would be okay — and he was. It turned out to be a much more serious problem, a life-threatening one, after he got back.

It would be easy to demonize Scott, the mission’s commander, for not inquiring further with Mission Control as to why only he and Irwin were being nudged to take sedatives for sleep. But Scott, too, was not made aware of Irwin’s condition until after the crew returned to Earth. The anger in Scott’s words is palpable:

I later became concerned that I had not been informed of this at the time and so could not take it into consideration when making my decisions as commander…had I been informed of this at the time I might have been able to simplify his role during the EVAs to reduce the strain on him…I tried, unsuccessfully, for several years to get NASA to provide an adequate explanation of the effect of Jim’s heart problems during the mission on the eventual decline in his health.

Would Scott and Worden both have nixed the record-breaking deep space EVA if they’d known about Irwin’s heart problem? My answer is yes. Worden later wrote in Falling to Earth, “If I had known that Jim, now blocking the hatch, had heart problems, I may have felt much less secure. If he’d had a heart attack at that moment, we’d all have been in danger.” It would be hard to believe that Scott, as mission commander, wouldn’t have agreed with that assessment. This would have meant that Thomas “T.K.” Mattingly, Apollo 16’s command module pilot, would have made the first deep-space EVA, but it’s also my belief that Worden wouldn’t have regretted this decision had it further protected his crew from any possible emergencies.

Moreover, Scott suggested he would have simplified Irwin’s EVA roles had he been aware, so it’s also possible he would have taken Irwin’s position in Endeavour’s hatch.


The immediate solution to Apollo 15’s potassium problem was introduced to the crew of April 1972’s Apollo 16 in the form of a potassium-laced orange drink that infamously caused mission commander John Young to develop what he called “the farts.”

Apollo 16’s moonwalkers, John Young and Charlie Duke, imbibed a potassium-laced orange drink in a bid to avoid the heart rhythm irregularities plaguing Scott and Irwin. 1972 NASA photo: “This is the Apollo 16 lunar landing mission crew portrait. Pictured from left to right are Thomas K. Mattingly II, Command Module pilot; John W. Young, Mission Commander; and Charles M. Duke Jr., Lunar Module pilot. Launched from the Kennedy Space Center on April 16, 1972, Apollo 16 spent three days on Earth’s Moon. The first study of the highlands area, the landing site for Apollo 16 was the Descartes Highlands.”

It’s not known whether Irwin’s issues changed the culture of how NASA handled in-flight health emergencies during the 1970s, as the closest thing that could’ve been considered problematic afterward was astronaut William Pogue throwing up during the first leg of Skylab 4’s 84-day-long mission, and the crew’s subsequent attempt to cover up his sickness in order to escape reprimands from the ground (spoiler: they were reprimanded, anyway). At present time, health issues in low Earth orbit are not only acknowledged but are tackled with an openness that wasn’t present during Apollo 15’s 12 days in space. The story of an ISS crewmember who suffered from a deep vein thrombosis in the jugular vein has been shared industry-wide as a case study in how to tackle potentially dangerous issues during long-duration missions. More recently, astronaut Mark Vande Hei suffered from a pinched nerve in space, which he freely acknowledged, and admitted it caused him to postpone an EVA.

Perhaps a culture of openness could have extended Jim Irwin’s life, but we may never know. After enduring several more heart attacks and a bypass operation, Jim Irwin died at age 61 on August 8, 1991. After his first 1973 heart attack, Irwin wrote in To Rule the Night:

I am a stubborn man, but now the Lord has my attention. I know I need help, and I am willing to accept it. I am grateful as the Lord reveals His plan for this flight, the Highest Flight of all.



Chaikin, A., & Hanks, T. (2007). A Man on the Moon: The Voyages of the Apollo Astronauts (Illustrated ed.). Penguin Books.

Irwin, J. B., & Emerson, W. A., Jr. (1982). To Rule the Night (First Holman Softcover Edition). Holman Bible Publishers.

Leonov, A., Scott, D., Hanks, T., & Armstrong, N. (2006). Two Sides of the Moon: Our Story of the Cold War Space Race (Reprint ed.). St. Martin’s Griffin.

Worden, A., & French, F. (2012). Falling to Earth: An Apollo 15 Astronaut’s Journey to the Moon (Illustrated ed.). Smithsonian Books.

Worden, A., & French, F. (2021). The Light of Earth: Reflections on a Life in Space (Outward Odyssey: A People’s History of Spaceflight). University of Nebraska Press.

Many thanks to Francis French, Eleanor Ann O’Rangers, Mark Rigby, and Beth Walloch for their editorial suggestions, and assistance with sources.


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Emily Carney

Emily Carney

Space historian and podcaster. Space Hipster. Named one of the Top Ten Space Influencers by the National Space Society. Co-host of Space and Things podcast.