Project Mercury – One small step for NASA

2021 marks 60 years since NASA’s Project Mercury got underway. A series of six single-person spaceflights – the first of their kind for the agency – it aimed to prove whether the most basic human functions were possible in space. Could a human eat and drink in zero gravity? Could they sleep? Could they even survive?

Spanning from May 1961 to May 1963, each Mercury mission was more complex than the last. From a 15-minute suborbital lob that proved the spacecraft worthy to a 34-hour challenge that proved the astronauts worthy, here is a rundown of those six flights.

An artist’s impression of the Mercury spacecraft with the launch escape tower (that would pull the spacecraft to safety if anything compromised the rocket) attached | Credit: NASA

Freedom 7 – Alan Shepard

Beaten to the title of ‘first person in space’ by Yuri Gagarin by less than a month, Alan Shepard launched from Cape Canaveral on 5 May 1961 as the first American in space instead.

His spacecraft had a periscope rather than a window (which would be introduced for the next flight) – he had fitted a filter over it while waiting on the launchpad to block out glare from the sun, but forgot to remove it before lift-off. It meant that when he looked through the periscope at Earth, everything was in shades of grey. He thought about removing it, but when he reached for it his glove banged against the abort handle. He decided not to push his luck.

Freedom 7 was a suborbital flight, a straight-up-straight-down affair that lasted just 15 minutes. Shepard experienced only five minutes of weightlessness, but it was a necessary step that NASA needed to take to prove that their astronauts could survive and operate in space.

Alan Shepard sits inside his Mercury spacecraft | Credit: NASA

Liberty Bell 7 – Virgil ‘Gus’ Grissom

Gus Grissom’s mission – which took place on 21 July 1961 – was designed as a repeat of Shepard’s to prove that it hadn’t been a fluke.

Rightly or wrongly, it is best remembered for what happened after it had come to an end.

The 15-minute spaceflight itself went without a hitch, but when Grissom was floating in the Atlantic afterwards waiting to be picked up by helicopter and transferred to a nearby aircraft carrier, the spacecraft’s hatch blew prematurely. Water flooded in and it sank to the bottom of the ocean. It took until 1999 for it to be located and recovered. Grissom himself narrowly avoided drowning, his suit also filling with water because of an open valve.

Despite some murmurings in the press at the time, Grissom was in no way responsible for what happened. The incident was attributed to a mechanical glitch.

A soggy Gus Grissom onboard the recovery ship after his mission | Credit: NASA

Friendship 7 – John Glenn

John Glenn’s flight was a step up in difficulty from Shepard’s and Grissom’s. It was the first crewed orbital flight that NASA had attempted, and would actually circle the Earth rather than just going straight up and down.

After a series of delays, Glenn launched on 20 February 1962. The rocket he was riding – a converted intercontinental ballistic missile that was more powerful than the Redstone used by Shepard and Grissom – had the tendency to blow up from time to time, but for Friendship 7 it performed as advertised and successfully got him into orbit.

Glenn circled Earth three times over the course of just under five hours. The reaction to his flight was unlike anything NASA ever anticipated. He became an instant national hero and by quite some margin the most famous of the original Mercury Seven astronauts.

Glenn inside his spacecraft during his mission | Credit: NASA

Aurora 7 – Scott Carpenter

Scott Carpenter’s flight – on 24 May 1962 – was designed to be a repeat of Glenn’s, much like Grissom’s had been a repeat of Shepard’s.

During the mission, Aurora 7 suffered a failure of its pitch horizon scanner, a part of the automatic control system that kept the spacecraft at the right angle relative to Earth. Carpenter had to manually correct for any errors, which meant he consumed more fuel than would be ideal.

Then, at the end of the mission, he accidentally used both the automatic and manual systems to start the re-entry process, consuming even more precious fuel from both tanks and almost completely draining what was left. This, combined with being three seconds late in firing his retro rockets, meant that he overshot his planned landing site by some 250 miles. It took nearly an hour for the US Navy to find him.

Despite this, his 5-hour-long flight was still considered a success.

Carpenter arrives onboard the USS Intrepid after his mission | Credit: NASA

Sigma 7 – Wally Schirra

Sigma 7 is the most likely flight of the bunch to be overlooked in documentaries, because it was so textbook perfect that there isn’t much of note to say!

Forget any science experiments, Schirra wanted his mission to be a pure engineering test flight. Go up, evaluate the spacecraft, come back.

On 3rd October 1962 (in the middle of the Cuban Missile Crisis) he did just that, making six orbits of the planet over the course of nine hours. There was barely a glitch to speak of.

At the end of the mission, Schirra was winched onboard the recovery aircraft carrier. However, rather than have technicians diffuse and then remove the hatch of the spacecraft, Schirra elected to blow the hatch himself. He had a point he wanted to make.

The recoil from the plunger sliced through the thick material of his spacesuit and left him with a big bruise down the length of his hand. It was his way of proving that Gus Grissom wasn’t to blame for the incident at the end of his mission, as post-flight medical records showed Grissom didn’t have a scratch on him.

Schirra in his official Mercury portrait | Credit: NASA

Faith 7 – Gordo Cooper

Just when NASA thought they had it nailed, Gordo Cooper suffered the worst technical problem of the programme.

Launched on 15 May 1963 and landing the following day, Faith 7 was NASA’s first spaceflight to last more than 24 hours. Cooper therefore became the first American to sleep in space.

30 hours into the 34-hour-long mission, the spacecraft experienced a short-circuit, leaving several crucial systems without power. Cooper had to make do with drawing lines on the window to work out what angle to come back through the atmosphere at and used his wristwatch to time the firings of his rockets.

He had to fly the entirety of re-entry manually, but despite this still managed the most accurate landing of all of Project Mercury and brought the programme to a successful end.

Cooper prepares to be extracted from his spacecraft at the end of Faith 7 | Credit: NASA

Delta 7 – Deke Slayton – The flight that never was

Deke Slayton was originally meant to make the follow-up to John Glenn’s flight. However, he was abruptly pulled from the mission just a few months before his planned lift-off because of a heart condition that caused it to skip a beat every so often. NASA had known about it when they had selected him as an astronaut and had been fine with it because it didn’t affect him day-to-day.

In the build up to his flight, however, NASA’s doctors started to get cold feet and decided that they didn’t want to risk putting him in space in case something happened to him. They grounded him and replaced him with Scott Carpenter.

Around the same time, the Mercury Seven got wind of a plan to select an official to oversee the astronaut office. Rather than have an ‘outsider’ running the show, they decided to appoint Slayton to the position instead. He was effectively the ‘chief astronaut’ until the mid-1970s, when he finally got his chance to fly in space as part of the Apollo-Soyuz Test Project of 1975.

Slayton in his 1959 NASA portrait | Credit: NASA


Project Mercury paved the way for all of NASA’s future crewed space programmes. The idea of whether a human could spend even 24 hours in space seems inconsequential today with astronauts now frequently spending six months on the International Space Station, but it was a complete unknown back in the early 1960s.

Mercury had proven that NASA had been right to choose pilots as its astronauts, and that it could handle a variety of problems that could arise during a spaceflight. It allowed them to continue full tilt with their plan and move on to Project Gemini, the next stepping stone in the road to the Moon. You can read summaries of each of those missions here.

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