Our World Space Week series about the WISA Woodsat and the history of spaceflight continues with a wooden story.
The Soviet Union was undoubtedly the number one during the early days of the space age. Not only they sent the first satellite to orbit in 1957, but they also managed to study the moon with space probes first. All missions didn't go well or the results were very limited, but they did it and tried even more.
The United States was lagging behind but had ambitious plans also for lunar research even before President Kennedy's famous Moon speech in 1962.
NASA set up a plan in 1961 to get photos from the lunar surface. The technology wasn't ready yet for landings, so their plan was to crash to the moon and send back the photos as long as possible.
The program was called Ranger, and the spacecraft developed were very simple and rudimentary: two solar panels for getting electricity, cameras pointing to the direction of flight, accompanied by computers and radio equipment, and an antenna pointing towards Earth. The plan was to send them to a collision course towards the moon and basically just receive the photos to the last moment before impact.
The program didn't start well: the first two Rangers were left stuck on low Earth orbit. After these NASA's Jet Propulsion Laboratory wanted to upgrade the probes with a science payload that was supposed to survive the impact and send back data.
But how to protect the seismometer that was planned to put inside the brach-proof capsule?
The answer was wood, balsa wood. The instrument was surrounded by a 65-centimeter diameter balsa ball, that would absorb the shock and possibly bounce and roll some time until coming to rest.
It was a great idea and was then used in Rangers 3, 4, and 5.
Unfortunately, all of those failed. Ranger 3 veered out off the course, flew by the Moon and ended in interplanetary space. Ranger 4 said also "no" to the planned trajectory and crashed to the lunar far side. We don't know if the seismometer and its small transmitter worked or not.
And finally, Ranger 5 had a malfunction in the electric system and the solar panels failed to charge the batteries. Because of this, the trajectory correction failed and the spacecraft passed the Moon by about 700 kilometers. So it is also now in interplanetary space, going around the Sun.
The Rangers that followed were more successful, but they didn't have the seismometer and wooden ball.
After these, the Chinese have been using wood in space, but again in a very special way: the Fanhui Shi Weixing recoverable reconnaissance satellites had their re-entry modules coated with oak. It acted as the ablative material of the heat shield. These satellites made 26 flights between 1969 and 2006, and are according to our knowledge the last satellites using wood.
But WISA Woodsat will be first using wood as an integral part of its primary structure, making it very unique. The plywood is now used just like the composite materials, as it is in fact a natural composite, paving the way to new, greener ways of building the satellites.