Remembering John Houbolt: the Man Who Gave Us Lunar Orbit Rendezvous

John Houbolt demonstrating Lunar Orbit Rendezvous circa 1962. Credit: NASA.

The space community lost a colossus of the of the Apollo era last week, when John Houbolt passed away last Tuesday just five days after his 95th birthday.

Perhaps the name isn’t as familiar to many as Armstrong or Von Braun, but John Houbolt was a pivotal figure in getting us to the Moon.

Born in Altoona, Iowa on April 10th, 1919, Houbolt spent most of his youth in Joliet, Illinois. He earned a Masters degree in Civil Engineering from the University of Illinois at Urbana-Champaign in 1942 and a PhD in Technical Sciences from ETH Zurich in Switzerland in 1957. But before that, he would become a member of the National Advisory Committee for Aeronautics (NACA) in 1942, an organization that would later become the National Aeronautics and Space Administration or NASA in 1958.

It was 1961 when Houbolt made what would be his most enduring mark on the space program. He was working as an engineer at the Langley Research Center, at a time when NASA and the United States seriously needed a win in the space race. The U.S.S.R. had enjoyed a long string of firsts, including first satellite in orbit (Sputnik 1, October 1957), first spacecraft to photograph the lunar farside (Luna 3 in October 1959) and first human in space with the launch of Yuri Gagarin aboard Vostok 1 in April 1961. A young President Kennedy would make his now famous “We choose to go to the Moon…” speech at Rice University later the next year in late 1962. Keep in mind, in U.S. astronaut John Glenn had just made his first orbital flight months before Kennedy’s speech, and total accumulated human time in space could be measured in mere hours. Unmanned Ranger spacecraft were having a tough time even getting off of the pad, and managing to crash a space probe into the Moon was considered to be a “success”. The task of sending humans “by the end of this decade” was a daunting one indeed…

NASA would soon have a mandate to sent humans to the Moon: but how could they pull it off?

Early ideas for manned lunar missions envisioned a single gigantic rocket that would head to the Moon and land, Buck Rodgers style, “fins first.” Such a rocket would have to be enormous, and carry the fuel to escape Earth’s gravity well, land and launch from the Moon, and return to Earth.

A second approach, known as Earth-orbit rendezvous, would see several launches assemble a mission in low Earth orbit and then head to the Moon. Curiously, though this was an early idea, it was never used in Apollo, though it was briefly resurrected during the now defunct Constellation Program.

Credit: NASA
Three plans to go to the Moon. Credit: NASA.

But it was a third option that intrigued Houbolt, known as Lunar Orbit Rendezvous. LOR had been proposed by rocket pioneers Yuri Kondratyuk and Hermann Oberth in 1923, but had never been seriously considered. It called for astronauts to depart the Earth in a large rocket, and instead, use a small lander designed only to land and launch from the Moon while the spacecraft for Earth return orbited overhead.

Houbolt became a staunch advocate for the idea, and spent over a year convincing NASA officials. In one famous letter to NASA associate administrator Robert Seamans, Houbolt was known to have remarked “Do we want to go to the Moon or not?”

It’s interesting to note that it was probably only in a young organization like the NASA of the early 1960s that, in Houbolt’s own words, a “voice in in the wilderness” could be heard. Had NASA become a military run organization — as many advocated for in the 1950s — a rigid chain of command could have meant that such brash ideas as Houbolt’s would have never seen the light of day. Thank scientists such as James Van Allen for promoting the idea of a civilian space program that we take for granted today.

Even then, selling LOR wasn’t easy. The idea looked preposterous: astronauts would have to learn how to undock and dock while orbiting a distant world, with no chance of rescue. There was no second chance, no backup option. Early plans called for an EVA for astronauts to enter the Lunar Module prior to descent which were later scrapped in favor of extracting it from atop the third stage and boarding internally before reaching the Moon.

Once Houbolt had sold key visionaries such as Wernher von Braun on the idea in late 1962, LOR became the way we would go to the Moon. And although Houbolt’s estimations of the mass required for the Lunar Module were off by a factor of three, the story is now the stuff of early Apollo era legend. You can see Houbolt (played by Reed Birney) and the tale of the LM and LOR in the  From Earth to the Moon episode 5 entitled “Spider”.

Credit: NASA
The ascent stage of the lunar module on approach to the command module with the Earth in the background. Credit: NASA.

Houbolt was awarded NASA’s medal for Exceptional Scientific Achievement in 1963, and he was in Mission Control When Apollo 11 touched down in the Sea of Tranquility.

He passed away in a Scarborough, Maine nursing home last Tuesday, and joins other unsung visionaries of the early space program such as Mary Sherman Morgan. It’s sad to think that we may soon live in a world where those who not only walked on the Moon, but those who also sent us and knew how to get there, are no longer with us.

Thanks, John… you gave us the Moon.

13 Things That Saved Apollo 13, Part 12: Lunar Orbit Rendezvous

Very early concept diagrams, circa 1959, of the Saturn I, Saturn V and Nova C8 rockets. Source: Wikipedia


Note: To celebrate the 40th anniversary of the Apollo 13 mission, for 13 days, Universe Today will feature “13 Things That Saved Apollo 13,” discussing different turning points of the mission with NASA engineer Jerry Woodfill.

Going to the Moon was big. It was a giant stride in doing what had once been thought impossible. Initially many scientists and engineers had big plans for huge rockets akin to the ships imagined in science fiction: one piece vehicles that took off from Earth, landed intact bottom down on the Moon and had the ability to launch again from the lunar surface. But other rocket engineers had different ideas, and this caused some big arguments. The method of going to the Moon that eventually won out used — in part — a little lunar lander. This decision ended up being instrumental in saving the crew of Apollo 13. And that was big.

The three different Apollo flight modes. Credit: NASA

There were three different methods to choose from in reaching the Moon. One, called the Direct Ascent Mode, would have used the big Flash Gordon-like enormous rocket – which was known as a Nova class rocket –to fly straight to the Moon, land and return. Second, the Earth Orbital Rendezvous technique called for two not-quite-as big Saturn V boosters to launch and rendezvous in Earth orbit. In this mode, one rocket would carry a single Apollo vehicle and its crew, and the other, more fuel, which would be transferred to Apollo in Earth orbit, and then the spacecraft would head off to the Moon. The third option was Lunar Orbit Rendezvous which used only one three-stage Saturn V booster, and split the Apollo vehicle into two separate vehicles – a combined Command and Service Module (CSM), and a Lunar Module (LM).

Those familiar with NASA history know that Lunar Orbit Rendezvous was the final choice.

But this mode wasn’t an obvious choice, said NASA engineer Jerry Woodfill.

“At first, Werner Von Braun wanted to use the Nova class rocket Direct Ascent approach, and so did President Kennedy’s science advisor, ” Woodfill said. “But a group at Langley Research Center led by Dr. John Houbolt came up with the Lunar Orbit Rendezvous design. And most everyone ignored them at first.”

NASA engineer John C. Houbolt describes the Lunar Orbit Rendezvous concept at the chalkboard in July 1962. Image Credit: NASA

But Houbolt insisted the one-rocket system was not feasible. In a NASA interview Houbolt said, “It can not be done. I said you must include rendezvous in your thinking — to simplify, to manage your energy much better.”

Houbolt said it turned into a two-and-a-half year fight to convince people, but he and his team had the facts and figures to back up their claims.

Woodfill said one of his colleagues, former NASA engineer Bob Lacy was part of the discussions on which plan to use. “He said it was unbelievable,” Woodfill recalled. “They were debating in a meeting room at Langley about the best way to go to the Moon. One side was for sending a single vehicle requiring a huge booster to get it there. The other group wanted a two spaceship method. No one seemed agreeable to the other side’s approach. Tempers were starting to flare. To ease the situation someone said, ‘Let’s flip a coin to settle the score.’ Can you believe that?”

No one flipped a coin, but the story demonstrates the intensity of the debate.

In the race to get to the Moon, the Soviet Union had embraced the Nova rocket concept. “The Soviets pressed forward with the direct assent approach to use a Nova class booster,” said Woodfill. “Designated N-1, it clustered 30 engines on its first stage. The design achieved a Herculean thrust of 10-12 millions pounds. Additionally, this uncomplicated direct ascent launch would be less complex was thought to take less time to accomplish. Designing, building, testing and launching two separate spaceships might not win the race to the Moon.”

Woodfill said the Nova rocket may have proved to be the best choice except for the failure of just one of those 30 engines at launch. “This would unbalance the entire assemblage,” Woodfill said.

And twice in 1969 – one occurring just weeks before the scheduled launch of Apollo 11 — the Soviet N-1 booster exploded at liftoff. The huge rocket proved to be too complicated, while the Lunar Orbit Rendezvous method had a simple elegance that was also more economical.

A diagram of the lunar-orbit rendezvous used on Apollo by John Houbolt. Credit: NASA

In November 1961, Houbolt boldly wrote a letter to NASA associate administrator Robert C. Seamans, “Do we want to go to the Moon or not?” he wrote. “Why is Nova, with its ponderous size simply just accepted, and why is a much less grandiose scheme involving rendezvous ostracized or put on the defensive? I fully realize that contacting you in this manner is somewhat unorthodox,” Houbolt admitted, “but the issues at stake are crucial enough to us all that an unusual course is warranted.”

The bold move paid off, and Seamans saw to it that NASA took a closer look at Houbolt’s design, and surprisingly, it soon became the favored approach – after a little debate..

Houbolt’s design separated the spacecraft into two specialized vehicles. This allowed the spacecraft to take advantage of the Moon’s low gravity. The lunar lander could be made quite small and lightweight, reducing bulk, fuel, and thrust requirements.

The Lunar Module Aquarius, after it was jettisoned from the CSM. Farewell Aquarius, we thank you, the crew radioed. Credit: NASA

When the oxygen tank in Apollo 13’s Service Module exploded, the Lunar Module “Aquarius” played an unexpected role in saving the lives of the three astronauts, serving as a lifeboat to return the astronauts safely back to Earth. Additionally, its descent stage engine was used for propulsion, and its batteries supplied power for the trip home while recharging the Command Module’s batteries critical for re-entry. And with ingenuity of Mission Control the LM’s life support system – which was originally designed to support two astronauts for 45 hours, — was stretched to support three astronauts for 90 hours.

Imagine, Woodfill said, if Apollo 13 had been a single vehicle employing the Direct Ascent approach. “After the explosion and subsequent loss of the fuel cells, only those entry batteries would have been available to sustain life. Their life, even if all systems except life support, were turned off would be less than 24 hours. And Lovell, Swigert and Haise along with Apollo 13 would return to Earth on that “free-return-trajectory” being cremated in the fiery heat of reentry. But for the clever Lunar Orbit Rendezvous approach, Apollo 13 would have been a casket. Instead, its lunar lander became a wonderful lifeboat” Woodfill said.

Next: Part 13: Houston

Earlier articles from the “13 Things That Saved Apollo 13” series:


Part 1: Timing

Part 2: The Hatch That Wouldn’t Close

Part 3: Charlie Duke’s Measles

Part 4: Using the LM for Propulsion

Part 5: Unexplained Shutdown of the Saturn V Center Engine

Part 6: Navigating by Earth’s Terminator

Part 7: The Apollo 1 Fire

Part 8: The Command Module Wasn’t Severed

Part 9: Position of the Tanks

Part 10: Duct Tape

Part 11: A Hollywood Movie

Part 12: Lunar Orbit Rendezvous

Part 13: The Mission Operations Team


Your Questions about Apollo 13 Answered by Jerry Woodfill (Part 1)

More Reader Questions about Apollo 13 Answered by Jerry Woodfill (part 2)

Final Round of Apollo 13 Questions Answered by Jerry Woodfill (part 3)

Never Before Published Images of Apollo 13’s Recovery

Listen to an interview of Jerry Woodfill on the 365 Days of Astronomy podcast.