With it being the 50th anniversary of the first Moon landing this year, Space Hub Perth (SHP) was keen to explore a Perth – Apollo connection that perhaps, not many people know about. That connection is Professor Brian J. O’Brien, a Perth local who worked on the Apollo program back in the 1960s and 70s. He graciously invited us to his place and spent time discussing his research on Moon dust, his experiences with the Apollo program, as well as showing us space memorabilia. He is a leading expert on Moon dust.
In the late 1950s, Professor O’Brien was a young assistant to the then Associate Professor James van Allen at the State University of Iowa, USA. Van Allen discovered the radiation belt surrounding the Earth that is now named after him. In the early 1960s, Professor O’Brien was building rockets and satellites at Rice University, USA, with his students, as well as developing high quality radiation detectors. It was these detectors that led to his involvement with the Apollo program.
At the time, NASA wanted to place experiments on the Moon to measure the lunar environment long after the astronauts had left. He submitted a proposal for a Charged Particle Lunar Environment Experiment (CPLEE) and in 1965, it was one of seven selected from a batch of 90 submissions, to fly to the Moon.
Professor O’Brien became involved with Moon dust through serendipity. In Los Angeles in early 1966, during a principle investigator briefing for the Apollo Lunar Surface Experiment Package (ALSEP), which would contain his CPLEE, he was advised by two companies bidding to build the ALSEP that his CPLEE would need a dust cover over its aperture. This was to protect the experiment in case dust was blown onto it when the astronauts blasted off from the Moon’s surface. As there were no close-up pictures of the Moon’s surface at that time, no one knew for sure about the dust situation there, but they decided to take this precaution anyway. However, the addition of a dust detector to measure what might be there was initially ruled out due to weight and astronaut time constraints. Not taking no for an answer, Professor O’Brien invented a dust detector on his flight home to Houston, post-briefing. It was both light-weight, at 270 grams, and required no astronaut time to be deployed. This detector was eventually included in the ALSEP and became known as the Apollo Dust Detector Experiment (DDE). In doing so, he became the only principle investigator with two different experiments on the Moon. The DDEs were successfully deployed on Apollo’s 11, 12, 14 and 15. They operated for many years, generating data that led to multiple peer-reviewed discoveries. Dust was now the main environmental challenge for astronauts and equipment on the Moon, and it continues to be so today.
The experiments sent to the Moon were covered in gold and silver materials in order to reflect sunlight and reduce their rate of heating. Without an atmosphere protecting it, the surface of the Moon is exposed to direct sunlight, heating up to above the temperature of boiling water. With daytime lasting around 13.5 days, preventative measures were needed to avoid the experiment’s electronics overheating.
It was anticipated that dust would cover everything on the Moon surface. By sticking to the gold and silver materials and discolouring them, dust would reduce their reflectivity and their ability to prevent overheating. The obvious problem that Professor O’Brien noted was that you’d need to measure the amount of dust causing the discolouration, which in turn resulted in the additional heating. Unlike previous, complex dust experiments that measured individual cosmic dust particles, one particle at a time, the ability to measure the effect of billions and trillions of low energy dust particles was required instead.
Professor O’Brien’s mid-flight DDE invention was a simple one. He decided to use a solar cell to measure dust, knowing they were reliable from his previous experience with building and launching satellites into space. Three solar cells were arranged orthogonally, facing East, West and up, ensuring at least one of the cells would always receive sunlight during the lunar day. He further refined this design, so that it both measured the cause of the heating (i.e. dust amount) and the effect of the heating (i.e. temperature), by placing a ball thermometer behind each solar cell. Professor O’Brien said, “I always liked to measure cause and effect in the one experiment.”
Dust moves on the Moon’s surface at a rate of about one millimetre per 1000 years, effectively smoothing the surface. That’s why the Moon looks the way it does even though it’s been bombarded over the last four billion years.
Dust particles are cohesive. In an experiment that was forgotten for 40 years, when astronaut Alan Sheppard splashed Moon dust onto two aluminium plates which had stamped identification numbers, the dust accumulated in the number indentations. When Sheppard then bumped the plates, the dust dislodged from the indentations and retained some of the shape of the numbers. Professor O’Brien refers to these as ‘magic numbers’ and humourously says, “If I were a teacher of STEM, I’d say [to the kids] that the only objects ever built with lunar dust are numbers.”
The top two centimetres of the lunar surface, where the dust is, is ‘extra-terrestrial’. That is, it’s a dusty plasma, electrically charged, bathed by ultraviolet light and the solar wind which deposits into it nuclei such as hydrogen and helium that were in the outer atmosphere of the Sun only one or two days earlier. It is chemically active.
Millions of years of meteorite impacts on the Moon has formed dust particles that have jagged and hooked edges. Not only does this make the dust abrasive, but together with the dust’s electrical charge, makes it very sticky. It was a noted problem for the Apollo astronauts.
Dust samples were accidently brought back to Earth on Moon rocks. However, the dust degraded the seals on the boxes containing these rocks, resulting in the Moon vacuum being contaminated by Houston air, rendering the dust inert.
At Microsymposium 60 in Houston this year, lunar scientists from the nine commercial firms that NASA is sending payloads to the Moon for agreed for the first time that dust was a significant problem and that payloads needed to have dust detectors.
Professor O’Brien helped Radio Australia in Sydney broadcast the Apollo 11 launch 50 years ago. When asked about the landing, he said, “The weird thing is I cannot remember to this day exactly when I first saw Neil walk down the ladder. “ He continued, saying confidently that, “As far as I was concerned, it was part of the mission and it was going to happen.”
Finally, Professor O’Brien was the first Australian to receive the NASA Medal for Exceptional Scientific Achievement.
NASA has plans to send the first woman and next man to the Moon by 2024. Other nations and other organisations also have ambitious plans for the Moon. From the discussion with Professor O’Brien, Moon dust is going to be a challenge that will need to be addressed by both the scientific and commercial communities. The research that he has pioneered brings us one step closer to solving the Moon dust challenge. For further information, visit Professor O’Brien’s website, www.brianjobrien.com, or search ‘Moon dust’ online. A complimentary video to this article can be found here.
Space Hub Perth is a volunteer group that’s helping to build a coordinated space industry here in Western Australia. You can follow Space Hub Perth on LinkedIn, Facebook, Twitter, Instagram and Meetup. Space Hub Perth is supported by CORE Innovation Hub, which is Australia's first co-working, collaboration and innovation hub focused on the resources industry.