Crew Mobility for Lunar Surface Operations
Robert Ambrose, William Bluethmann, Lucien Junkin, and Dan Harrison
NASA, Johnson Space Center, Houston Texas
Abstract
Two forms of surface mobility for astronauts will be described, generally referred to as pressurized and unpressurized rovers. The Apollo Lunar Roving Vehicle (LRV) was an example of an unpressurized rover, able to carry two suited crew with a small additional payload. Larger unpressurized rovers will be described that are able to carry larger compliments of crew, as well as carry the payloads being identified by NASA’s lunar architecture studies. The description of these unpressurized rovers will include results from field testing of LRV class testbeds such as NASA’s Science Crew Operations and Utility Testbed (SCOUT)rover shown in figure 1 as well as the more recent testing of the Chariot system in figure 2 designed to meet the Constellation Program’s larger crew and payload requirements.
New approaches to mounting suited crew onboard these rovers will be described, looking beyond the seats employed by Apollo. Improved range, comfort, visibility, egress, and access to surface data systems are major advances over Apollo era machines. The relationship of rovers to suited emergency walk-back requirements will be described, as well as other requirements for performance now being defined for lunar operations.
Figure 1 Apollo LRV (Cert Unit Testing) and SCOUT (Arizona Field Testing)
Figure 2 Chariot Rover (JSC Rockyard Testing)
Pressurized rovers are the second form of crew mobility to be described. Where unpressurized rovers require the crew to ride and/or drive while wearing space suits, a pressurized rover has a cabin that allows the crew to ride and/or drive in a shirt-sleeves environment. Pressurized rovers have many other capabilities, such as radiation protection, longer range than the limits of suited EVA, and airlock/port interfaces for allowing the crew to transition to suited EVA for the best of both approaches. Recent work on a Small Pressurized Rover (SPR) shown in figure 3 will be described The SPR will be mounted onto the same Chariot mobility chassis tested as an unpressurized rover. In addition, suit port interfaces will be reviewed in terms of their integration with the mobility chassis and cabin.
Figure 3 Small Pressurized Rover Concepts with internal crew, and docked to Lunar Outpost
These future rovers will be driven both with onboard crew, as well as without crew. Uncrewed roving will allow for ground supervised operations when crew are not present on the lunar surface, or for crew living inside habitats to preposition rovers for their shared use. These uncrewed driving modes were first demonstrated on the SCOUT vehicle in 2005, 2006, and 2007 Arizona field testing, with operations from Houston Texas over delayed communication paths. Delays of 5-10 seconds will be experienced when supervising rovers on the lunar surface. Field test results show that a supervisory level of command and control will suffice if the vehicle has a low level of automation. Onboard driving skills such as obstacle avoidance, slip detection, over angle (tipping) detection and subsystem fault detection will protect a machine from damaging itself, allowing the supervisor to detect and then resolve longer term problems once the rover has placed itself into a safe state.
Surface crews inside habitats or pressurized rovers can operate other rovers across low latency communication. Unlike the ground supervisors, these operators will be able to drive the rovers in real time using cameras or other sensing. Combinations of control modes are also possible, with a driven rover being followed by uncrewed rovers driving under ground supervision. Control mode transitions between onboard driving, surface to surface teleoperation, or ground supervision will require safe and verifiable handoffs, especially when dismounted crew are conducting EVA’s near the rovers. Results from these field tests will be used to establish and refine flight rules to govern the safe application of this technology for lunar surface operations.