How will we get around on the moon? Mobility is a primary need and it will be important to have a reliable way to move people and things in order to do the science we want to do and collect the resources we need. The Apollo rover had some design innovations, where have we come since then and what does the future look like for lunar surface transportation?
The Apollo lunar rover used to drive around on the surface of the moon was a fascinating vehicle who’s history really demonstrates the enginuity and ambition of the engineers of the day.
Early iterations of the Apollo mission had two rocket launches per manned mission. The first rocket would bring supplies to the surface of the moon and the followup would ferry the astronauts. With this double launch mission there would have been far more payload capability for launching a small habitat or mobile laboratory. In fact, the MOLAB vehicle was prototyped to fit this concept. It was a pressurized mobile laboratory suitable for two people to stay in for extended missions of driving around the moons surface. Almost like a lunar RV.
Eventually however the double rocket mission profile was scrapped and as a result it was impossible to bring along a vehicle with everything else on a single rocket. So MOLAB and other contracts to develop lunar vehicles were scrapped.
Thankfully two engineers kept hacking on ideas to bring a vehicle with the Lunar Module.
There wasn’t much free space to be found on the lunar lander to work with. But there was one small unused space on the lander between the landing legs. The engineers spent some time designing a very small vehicle that would fold down to fit into that space.
The concept of a very small foldable battery powered electric car for two astronauts was presented to Werner Von Braun just 2 weeks before the Apollo 11 launch that landed astronauts on the moon. This presentation consisted of little more than a remote controlled toy car sized model design concept. It was then that it was decided that we had to have this vehicle for getting around on the moon for later Apollo missions.
In what was a strikingly tight timeline NASA wanted to have a flight ready vehicle for Apollo 15 which left them with just 18 months to go from scale model mockup to a vehicle on the moon astronauts could use, including training vehicles that astronauts could use before then to simulate missions with.
In the ensuing 18 months several challenging design issues would need to be solved. In particular, the wheels, the controls, navigation, folding, power, and the seating.
One of the most apparent unique features of the lunar vehicle was it’s metal tires. This was an entirely new concept at the time and much work was put into finding the best way to weave the metal together to provide cushioning, strength, traction, and be wear resistant against the abrasive lunar regolith. Standard rubber tires would have been too heavy, and also short lived in the extreme temperatures of the moon. The wheels were designed and manufactured by General Motors, and needed to support two astronauts, and half a ton of collected rock samples.
On the lunar rover, each of the 4 wheels was powered by it’s own dedicated ¼ hp electric motor that allowed the rover to reach speeds of 13kph. Power was delivered from non-rechargable batteries that delivered a range of 57 miles (90km). It also featured front and rear power steering controlled with a joystick. Incredible features for a car designed in the early 70s.
Navigation is perhaps more important than we would naively realize. Due to the smaller size of the moon, you don’t have to travel far to go over the horizon, and with similar grey dusty landscape in all directions, and no magnetic field to use a compass with, or detailed maps it would be extremely easy to get lost. With the limited computer capabilities of the late 60’s NASA was able to create a rudimentary navigation system that measured how far and in what direction the vehicle had gone by measuring the direction and rotations of the wheels. It could point back to the landing site.
The folding concept of rover is what made it possible to pack it to bring along to the moon. It had to fit into a rather tight triangular shaped space on the outside of the lander between the legs. In order to fit, the seats had to be able to fold flat into the floor, the floor had to fold in half and the wheels had to fold up into the remaining space. This complex origami folding would have to be done by just two astronauts wearing bulky space suits quickly so they don’t have to spend hours assembling a car.
Perhaps the biggest surprise was the difficulty in designing seating that would work in the lunar gravity. Late in the development, a prototype was flown in a low gravity simulator aircraft and a critical flaw was discovered. The bulky and stiff spacesuits combined with lower gravity made it nearly impossible to sit down. Had they launched the Apollo 15 mission without having completed this simulation it’s likely that the astronauts wouldn’t have been able to use the rover when they got it unpacked on the moon. Luckily a quick fix of adding a foot rest provided the necessary leverage required to twist into the seat.
The Apollo era vehicle was a brilliant piece of technology, put together in an insanely tight timeline. Having the car on the moon opened up some spectacular discoveries that would not have been possible without it. By covering dramatically more ground the astronauts were able to find and collect more interesting samples than they would have with a bag and shovel on foot.
In the later Apollo missions the rover played an outsized role, it was central to the discoveries that were made and was prominent in everything that happened on the surface of the moon.
Now as we are looking again at getting back to the moon there has been much development work on how to provide mobility on the lunar surface. Much of the focus has been on robotic rovers since until recently it seemed we would have lots of time to design a new crewed rover before we put people back on the moon. With the new 2024 NASA goal to get people back on the moon there could be new impetus to develop a modern lunar vehicle.
NASA has developed several proof of concept lunar rovers over the last decade or so. The SEV is the conceptual successor to the Apollo lunar vehicle. It is modular and pressurized, not unlike the rover used in The Martian movie starring Matt Damon. It’s a big vehicle and landing one on the moon will be a feat.
There is still much work to design the mission that will put people back on the moon in 2024 and so far, there has been very little detail about what vehicles we might see driving around up there when the time comes.
NASA may be waiting to see how the commercial partners are able to accelerate their plans for providing lunar delivery services, and what payload options it will open up before setting the design requirements for a rover that will actually get to the moon in the next 5 years. At the time of recording there hasn’t been much news about lunar vehicles that have a real chance of being part of this next crewed mission to the moon, but it’s important that we get a vehicle up there for them.