SHORT REPORT ON THE MAY 1998 EVA TEST AT METEOR CRATER, ARIZONA
Nathalie A. Cabrol and Edmond A. Grin, NASA Ames Research Center
Introduction
The Extra Vehicular Activity (EVA) suit has been tested during two weeks in Meteor Crater, Arizona. We were invited by the EVA group of Johnson Space Center to observe their test. We joined the group of the NASA Johnson Space Center led by Joe Kosmo, thursday 14th 1998, on the North rim of Meteor crater (Fig.1). Our goal was to make observations that would help us prepare our joint ASRO project and try to document some questions, such as for example: what a rover can do that an astronaut cannot ? Who is better at what ? This is not just a matter of simple challenge between humans and machines. The goal is to identify the aeras in which both are complementary and can interact with effectiveness. A common remark is to say that humans are better than robots to explore planetary surfaces . This is true in many cases but nobody tried yet to quantify their respective performances. This is one of the objectives of the ASRO project.
Fig.1 Meteor Crater south rim as seen from the test site.
The steep and resistant layered scarps are well-observed and can prove
to be a serious hazard for astronauts to investigate craters. Eroded and
collapsed walls will be an alternate possibility to reach and explore their floor.
The objective of our visit was to collect information about the performance of an astronaut in a planetary surface exploration configuration before the rover field experiment of Silver Lake (Ca) in february 1999. In Silver Lake, the astronaut and rover will be associated for the first time. The goal of the operation we observed in Meteor Crater was for the trained suited subject, Dean Eppler, who is a geologist also, to perform a series of tasks while wearing a pressurized suit. The tasks involved the achievement of 12 traverses with:
- stops to perform geology;
- mobility in various slopes and soil configuration;
- the setting of mockup instruments and stations (a generator, meteorological stations, a sismometer, a magnetometer, and gas release stations).
The astronaut was in the EVA unit at 10:45 a.m. and the operation lasted for about 40 minutes.
Operation Description
Although the time requested for Dean Eppler to pull on the suit and be ready for the operations was not too long, several persons were necessary to help him with the fixation of gloves, boots, and helmet. The whole operation took about twenty minutes, to which the time necessary to prepare the air-supplier has to be added. As the filling of the air-tank was already going on when we arrived at the site, we cannot tell the total duration of the operation. Then, Dean isolated from the outside environment in the pressurized suit was freed from the trail to which the suit was attached. The contact between the astronaut and Joe Kosmo the test leader and some members of the Team was kept using a microphone. Since we were wearing hearset, we could hear Dean describing the environment, detailing each operations, and performing geologic interpretation of the site. Once free from the trailer, Dean walked to stop No.1 (Fig.2). The mobility (walking with the suit) did not seem to be a problem in terrestrial gravity and Dean rated it with an A. The first stop demonstrated some of the limitations generated by the suit, especially when the astronaut wants to reach an object on the ground, and diverse technical aspects that will require more study (see Fig.2). It also almost immediatly pointed areas where rovers will be important additions.
Fig.2Stop #1. A technician is holding geologic tools
to Dean (hammer, ice axe, magnifizer). During this stop, the astronaut performed
geologic operations: selection of a representative sample of shocked rock
(extracted from in situ outcrop), retrieval of the sample, and hand and magnifizer
inspection.
Four items captured our attention:
- As seen on Fig 2., a technician holds the tools for the astronaut. If following this configuration during planetary surface exploration, it would take at least two astronauts on the field at the same time for a unique operation. Although this sounds reasonable for security reasons, it seems that two astronauts on the field at the same time should no be tighed one to each other for the same task (for instance, the second astronaut being an assistant to the first one). This is probably one area where the presence of a rover as a field assistantcould be helpful, save time and increase the effectiveness to a field mission.
- During most of the science study operations (during stops), the astronaut looked totally entangled with his tools, either because the tools strap was caught in his glove, or because he was handling samples (see Fig.3).
Fig.3 Probably what one does not want to see during a planetary
surface mission. The astronaut is resting against the axe, the metallic part against the suit.
The necessity of having a rover used as a trailer is obvious in Fig.3. The lack of a rover with designed tools racks obliges the astronaut to rest on his axe in a dangerous position. The peak carried on his right arm while he is attempting a hand and magnifizer inspection of his sample is also far from efficient. The accumulation of diverse, cutting and sharp-pointed tools increases hazards and potential for accident that can be deadly (i.e.: the astronaut can loose his balance and fall on one of these instruments, the instrument sharp-pointed end may have the potential to tear off the suit). There is also a potential to forget a tool on one site. What seems to represent a minor problem on Earth will cost a lot on Mars or on the Moon. Going back to picking up tools will consume air-time and could jeopardize the completion of a mission operation. This area is probably one among those that seem to require the more work.
- The tools used for the science operations were not adapted to the tasks. A discussion with Dean after the operation seems to show that ergonomic study could definitively improve the size, and shape of the tools that have to be handled in a pressurized glove. The rover might help in some circumstances that will be tested during the ASRO experiment in Silver Lake. One typical example immediatly seen on stop 1, and that was to be repeated several times during the operation (see Fig.4, setting of stations), was provided by item No.4.
- Once the astronaut had selected the representative rock sample and extracted it by hammering the rock, he tried to bend down to collect the sample. The astronaut was stuck in the semi-rigid suit, his hand not being able to reach ground (short by at least about 30 cm). The solution he chose was to use the large part of his axe-plate to bring the sample at his hand level. Although Deam proved to be very dexterous and succeed after four attempts, it is not a solution to envision for planetary surface exploration. Two alternate possibilities exist to avoid this problem:
(a) adapt a nest-like tool on the axe itself to collect the samples, and/or
(b) have the rover doing this task for the astronaut. The same limitation was observed during the setting of the stations, where the astronaut could reach the ground, but could not either used his two hands, one being positioned on his knee to keep balance.
Fig.4 The right hand on the station, the left hand on his left knee,
the astronaut has to deal with the task to complete and the balance to keep. This position shows
the limit of bending stress that could be reached during the operation.
Conclusion
Overall this was an increbible and exciting experience. Watching Dean walking in his suit in the scenery of Meteor Crater projected us some 200 million kilometers away and several years from now, when the first human crew will walk at the surface of Mars. The Meteor crater test were performed using a semi-hard suit (H-suit). During the ASRO experiment, the astronaut will wear a new and completely soft suit (I-suit). The test also showed us better than any theory what performance can be achieved by a suited astronaut, and where humans and teleoperated and/or autonomous vehicles will be able to collaborate. This is a fascinating field to be explore by the ASRO project.
Photo Gallery
Here are some more photographs of Dean Eppler in the EVA suit during the test. (Copyright for the photographs: Nathalie A. Cabrol)
Photo 1: Earth or Mars ? Dean Eppler in the EVA suit stops to assess the local geology of the crater; Photo 2: hiking on loose soil slope material is not a problem for the suited astronaut that could challenge steep grades; Photo 3: The astronaut connects the cables between the different stations he just installed. Photographs by Nathalie A. Cabrol.
