I’m probably dating myself by telling you that I remember the summer of 1971.

Triumph had just released the T120R — probably the best of the Bonnevilles, thanks to a Rob North-designed frame that carried the oil in the backbone — but it was too little, too late to save the British bike industry from Honda’s 750-Four. Giacomo Agostini was in the process of winning another 500 grand prix title on his MV Agusta triple. Meanwhile, I was riding a 49 cc Puch "Condor" moped.

I suppose one of the few bikes I didn’t covet — that was even more mundane than my moped — was the Honda Z50 "monkey bike." (Note to the small-but-avid community of Z50 collectors: No offense intended!)

The thing is, something very like a Z50 easily could have become the world’s most famous motorcycle that July. That’s because NASA considered equipping Apollo 15 astronauts with electric minibikes to explore the surface of the moon.

NASA’s LRV "Rover" debuted on the Apollo 15 mission. A total of three of these vehicles, developed at a cost of $38 million, were left behind on the moon. NASA photo.

Long before the Apollo program, NASA had envisioned equipping astronauts with some kind of vehicle that would allow them to explore the moon’s surface. After the Soviet Union put the first man in orbit, John F. Kennedy brashly declared that the United States would send men to the moon and return them safely before the 1960s were out. NASA and the Apollo program became national priorities.

The first astronauts walked on the moon in 1969, but some kind of vehicle that allowed them to explore further afield from the Lunar Module (LM) was both scientifically attractive and offered yet another propaganda victory over the Soviets.

As you might imagine, various Buck Rogers-style rocket packs and small rocket runabouts were considered. Many wild and wonderful four-wheeled prototypes were developed and tested. Initially, concepts weighing over a ton were feasible, because the design brief called for two Saturn launch vehicles per mission. NASA considered pressurized vehicles that would allow astronauts to roam the moon’s surface for weeks at a time.

Inevitably, however, NASA’s budget was cut back, forcing them to build a Lunar Module that could be lifted into orbit and sent on its way to the moon with just one Saturn V. NASA still had its heart set on giving astronauts a vehicle to explore further afield. Boeing worked with General Motors’ defense research division on a lighter and more compact vehicle that could be packed into the LM.

The engineers working on it called it the "moon buggy" — a play on dune buggy. Those were popular back then. Officially, it was designated the Lunar Roving Vehicle (LRV); it became famous as, simply, the Rover. But even folding that minimalist vehicle into the available cargo space was a challenge.

Talk about ATGATT! Testing what appears to be a then-new Honda CT90 on a fake lunar surface. NASA photo.

In 1969, NASA was far from sure that Boeing and GM could actually deliver the moon buggy. So the Spacecraft Design Division, in Houston, decided to hedge its bets. Hmm… what’s smaller than a dune buggy, but offers similar off-road capabilities? Obviously, a dirt bike.

With its moon buggy, Boeing literally reinvented the wheel. The Rover had ingenious expanded wire mesh "tires" that solved the problem of rubber tires over-inflating in the absence of atmospheric pressure. But for its moon minibike, the Spacecraft Design Division chose an easier path. At the time, Honda was flooding the U.S. market with cheap, reliable trail bikes. As NASA’s own photos make clear, someone just went and bought one, to see if it could be controlled by a guy encumbered by a bulky space suit.

This looks like the same CT90, but this time it’s suspended from a rig intended to simulate the moon’s reduced gravity. At some point, it dawned on NASA’s engineers that at one-sixth g, a motorcycle would have to be leaned much further in turns. NASA photo. Photos from 1969 show a Manned Spacecraft Center engineer testing what appears to be a bone-stock Honda CT90 on a fake lunar surface, while suspended from an elaborate rig to simulate the lunar gravity (by taking up five-sixths of the weight of bike and rider).

Several Apollo astronauts were avid motorcyclists. (Neil Armstrong, the first man on the moon, rode a Montesa; Pete Conrad, who commanded the second moon mission, died after crashing his Harley.) But none of the engineers involved had ever designed a motorcycle. Maybe that was why they developed prototypes based on proven, commercially available models. Eventually, the full-sized lunar trail bike idea was rejected when someone realized that on the moon, a motorcycle would have to be leaned much further to make it turn.

John B. Slight, of the Manned Spacecraft Center, Flight Support Division, testing an early prototype under one-sixth gravity conditions aboard a KC-135 aircraft. This photo’s dated August, 1969, just a month after Boeing and GM got the go-ahead to develop the Rover. NASA photo.

NASA then tried something like an electric monkey bike. There’s a fascinating archival photo of one prototype being ridden in the famous "Vomit Comet" — a cargo plane that flew in a parabolic climb/dive pattern to simulate lunar gravity for 30 seconds at a time. The minibike in that photo just has ballast where the motor and batteries would go. (You can see that another NASA guy is pushing it. Interestingly, they’re trying it over a little ramp. Can you imagine how eager Travis Pastrana would be, to jump a motorcycle in one-sixth earth gravity?)

This image shows the most evolved prototype; something that looks like a functioning EV, again in the one-sixth g test rig. Although it’s still tiny, the wheelbase is longer and the handlebars are higher than the Z50’s. The test rider’s posture on the bike reflects the fact that in a vacuum, the astronaut’s pressurized suit makes it hard to crouch. NASA photo.

NASA went further, developing a working electric minibike with a 10-pound, five-eighths horsepower motor and a 30 amp-hour battery. Top speed was seven miles an hour. I’ve never been able to determine what battery chemistry they planned to use in the moon minibikes, but the Boeing/GM Rover relied on silver-zinc potassium, non-rechargeable batteries to power DC motors. That’s the same battery chemistry still used in applications, like watch batteries, that need high energy density. My best guess is that the motorbike used similar cells.

(I sent the photos accompanying this story to Lennon Rodgers, a friend of mine who once built a bike to race in the Isle of Man TT Zero event, and who previously worked for the Jet Propulsion Laboratory. He immediately noticed that the bike in the photos doesn’t have a battery pack big enough for the mission. He suspected it was just an early proof-of-concept that they built to see whether an astronaut could control it at all at one-sixth g.)

The AMA magazine imagined what it would have been like if minibikes had been used on the moon. What limited technical information I’ve been able to glean about this project came from a 1972 article in AMA News, the association's magazine of the time. Cooling the battery and motor was a challenge because there was no atmosphere to absorb heat. So NASA used the frame itself as a heat sink and added a "water jacket" to those components that was filled with beeswax. The idea was that the wax would melt and absorb heat. When things got too hot, the astronauts would stop long enough for the wax to re-solidify.

Unlike Boeing’s engineers, the minibike engineering team felt they could use rubber tires as long as they calculated what inflation was needed for tires to work properly in a nearly perfect vacuum. Astronauts’ suits also tend to inflate and feel almost rigid under those conditions, which is why the guy in the test rig is leaning forward and almost lying on the bike. They determined that it would be tiring to hold a normal sitting position. It also looks as if the electric test bike has a fork outfitted with an axle clamp that allows for testing radical changes in steering trail.

NASA always seemed to have photographers around, but they really weren’t that great about preserving their history. (One of the original Rover prototypes survived only because a scrap metal dealer recognized it and refused to put it in his crusher!)

When I first learned about the moon motorcycle program, I contacted the press liaison at the National Air & Space Museum. She inquired of the archivist for the Apollo program, who had never heard of it.

Luckily, my friend Lennon found someone at MIT who was familiar with the project. He learned that the minibike program was hampered because the cycles were hard-pressed to tow the Modular Equipment Transporter, a two-wheeled scientific cargo trailer that astronauts called "the rickshaw."

This is the astronauts’ Modular Equipment Transporter, aka "the rickshaw." I learned that the minicycles had trouble towing it in testing, but the end of the moon motorcycle project really came when the four-wheel LRV proved to be mission-ready in time for Apollo 15. NASA photo.

According to the Wikipedia article on the MET, NASA used it on the Apollo 14 mission and had planned to use it on Apollo 15 — perhaps with the lunar minicycle. Partway through Apollo 15’s mission planning, NASA revised the plan to use the LRV.

It only took Boeing and GM 18 months to deliver the Rover — in time for Apollo 15, thus rendering the minicycle obsolete before it ever had the chance to prove itself. The LRV fit in the available payload bay, and was just capable of carrying all the gear and lunar samples, so no towing capacity was required. The buggies worked perfectly, except for that one time when an astronaut accidentally broke off a fender. Temporary repairs (yes, with duct tape!) failed, and they were showered with moon roost for the rest of that mission. (None of the prototype scooters had fenders, but they obviously would’ve needed them.)

If any of NASA’s prototype EV minibikes have survived, no one at the agency seems to know where they are. (If any Zillans know where one is, please contact me!)

In the meantime, that AMA News cover is sure evocative, isn’t it? As it was, the Z50 was a popular model for Honda, and introduced thousands of American kids to motorbikes. Mint examples currently command astronomical prices on eBay. (You see what I did there?) Can you imagine how much more popular those monkey bikes would’ve been if they’d been used to explore the lunar surface?

Sadly for motorcyclists, as AMA News wrote in 1972, “NASA feels that four-wheeled vehicles are necessities and two-wheeled vehicles are luxuries. This… has always been basic to the American way of thinking.”

Too bad, because as one person on Reddit wrote, “Riding a motorcycle on the moon is by far the coolest thing a human being could do in the entire history of mankind. Nothing else comes close.” I agree.