Folding a Lincoln into a Volkswagen
April 10, 2000 -- Can you imagine what
might happen if your car broke down while you were driving ...
on the Moon?
No, Triple-A is not a cell-phone call away. A concerned motorist is not going to stop and lend a hand. And forget about walking home.
If this sounds silly, don't forget that about 30 years ago people actually were driving around on Earth's satellite. During three of the Apollo missions to the Moon in the early '70s, astronauts in bulky white space suits cruised the Moon's rugged gray terrain in their custom-designed "moon car."
Right: Pictured here during the Apollo 17 landing, the Lunar Roving Vehicle (LRV) (better known as the Moon Buggy) carried astronauts across the surface of the Moon during the Apollo 15, 16, and 17 missions. You can see the lunar rover in action by clicking on this RealVideo introduction (126kB) to NASA's Great Moonbuggy Race. credit NASA
The moon rover had to be large enough to drive over big rocks
and in and out of craters, but small enough to be tucked into
the astronauts' spaceship. It had to be strong enough to support
the astronauts and their heavy equipment, but light enough to
send to the Moon. And it must not break down -- the astronauts
couldn't risk getting stranded.
The importance of safety and reliability ruled out some of the more unusual designs. To find the best way to get around on the Moon, the engineers played with ideas for vehicles that walked, crawled, jumped and even flew over the Moon's surface, according to Vaughan.
"We had all kinds of different concepts, but it eventually came down to [this] -- we had to have something simple," Vaughan said. "And something simple was something like a Jeep."
But a regular Jeep would be far too heavy to launch into space.
"The other big crunch was weight," said Randy Simpson, a mechanical engineer who was fresh out of college when he was assigned to the lunar rover project. "It cost a lot of money to put something on the moon, so every ounce you could get out of that structure (saved money)."
The finished lunar rover weighed only about 450 pounds, or just 75 pounds in the Moon's one-sixth strength gravity. At the same time, the rover could carry up to about 1000 Earth-pounds -- more than twice its own weight.
"If you visualize your own automobile, it had to carry the equivalent of two more of your automobiles on top of your current car," said Saverio Morea, who was the project manager for the lunar roving vehicle at the Marshall Space Flight Center. "And it still had to be stable on a 45 degree slope."
To keep from tipping over on the Moon's hilly terrain, the rover's wheels needed to be as far apart as possible. But the rover also had to take up very little space when stowed aboard the lunar module, the astronauts' spaceship. To meet both challenges, the engineers designed the rover to fold up like a Transformer toy.
"A large automobile the size of a Lincoln today had to be folded into something smaller than a Volkswagen," Morea said. "It had to be very large yet very light."
Being light solved some problems, but created others.
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The Great Moonbuggy Race
The original lunar rovers may be hundreds of thousands of miles away, but the spirit of the moon buggy was alive and well this weekend right here on Earth. On April 7 and 8, 2000, students from all over the United States and Puerto Rico converged on Huntsville, Alabama to compete in NASA's 7th annual Great Moonbuggy Race. Each team of students brought along a homemade moon rover designed to solve some of the same engineering challenges as the original Lunar Roving Vehicle. Twenty-five teams in all raced their buggies around a course at the US Space & Rocket Center, navigating obstacles on a simulated lunar terrain. For a complete list of winners, click here.
Above: A RealVideo (126kB) introduction for the Great Moonbuggy Race, with some nice footage of the real Lunar Rover. credit NASA
The Great Moonbuggy Race is sponsored by the NASA Marshall Space Flight Center, the U.S. Space & Rocket Center, American Institute of Aeronautics and Astronautics, Sci-Quest, and the Alabama Aerospace Teachers' Association. For more information see http://moonbuggy.msfc.nasa.gov.
Traction was an issue. With so little weight pressing the
rover's wheels into the Moon's dusty soil, the engineers weren't
sure the rover could get enough traction to climb slopes with
the astronauts on board. To solve this problem, the engineers
put cleats on the wheels, and then put fenders on the rover to
control the moon dust that the cleats would kick up.
It didn't help the traction problem that people weren't certain what the lunar soil was like.
"Back in the early '60s they didn't know whether they would sink down into the moon when they landed on it," Simpson said. "There were some early probes that went to try and get an idea of the consistency of the surface, but nobody really knew whether that was the same all over the moon or whether it was just a particular place."
By the early '70s, though, information from the probes together with data from thermal, optical and radar studies of the Moon's surface allowed the engineers to make a good guess about the soil's texture, Vaughan said.
For the most part, he was right.
The lunar rover performed beautifully on the whole, allowing the astronauts to venture further from the landing sites and broadcasting panoramic shots of mountains, boulders and craters back to televisions on Earth.
A couple of unforeseen curve balls served as reminders of the importance of careful planning for missions into space.
"One of the scariest things that we had was on Apollo 15, when they went to take (the rover) out of the (lunar module) it wouldn't come out right," Vaughan said. "We were down there at Marshall trying to figure out how in the world we were going to get that thing out."
The rover was supposed to slide out of its holder on the lunar module using a little mechanism that wasn't working right. Engineers at Marshall Space Flight Center worked with a model rover for about an hour trying to figure out how the astronauts could get the rover free.
"The beauty of it is that the vehicle weighed [so little] that the astronauts were able to man-handle it down," Morea said.
The astronauts didn't have to worry about folding the rover back up, though. They left it behind on the Moon.
Today, three abandoned lunar rovers still sit on the Moon. With the exception of their plastic parts, they will probably be sitting there thousands of years from now -- a silent testament to 20th century engineering.
"It's been very meaningful to me over the years to see the rover in pictures and photographs and on the television -- it's still sitting up there on the moon," Simpson said. "I had a little bitty part in putting it on the moon for who knows how long."Web Links
7th Annual great Moon Buggy Race -- home page, from the Marshall Space Flight Center
Four-wheeling on the Moon -- Headline story on the Lunar Rover and the Great Moonbuggy Race.