NASA’s Ingenuity Helicopter and the Future of RPAS Missions and Systems
NASA’s “Ingenuity” helicopter was designed as an experimental technology demonstration with humankind’s first powered and controlled flight on another planet. The designs for the mission and mission system have critically relied on years of scientific observations of Mars, the Martian air and land operating environments, and the Sun-Earth-Mars integrated operating environment. The Ingenuity mission follows design principles that can be important considerations for remotely piloted air power on Earth.
Remote Pilots displaced in Space and Time
One Earth day is 23 hours 54 minutes while one Mars sol is 24 hours 40 minutes. The different lengths of day on each planet impact the cyclic predictions for when the communications network can connect and transfer signals between the Earth ground station and the Perseverance base station.
Furthermore, NASA requires that its Earthbound Mars mission workforce synchronise with the Martian sol cycle to be agile and responsive to any unexpected issues arising during the mission. The Earthbound workforce needs to cumulatively add 40 minutes to their daily routine, displacing their body clocks. Working to Mars time enables NASA mission planners, operators, and support crews to respond more quickly to the daily downlinked mission results, fault-finding, replanning, and timely uplink of commands for the next day’s mission on Mars.
Mars Air and Land Operating Environment
The Martian surface features a mix of terrain with canyons, dry lake beds, craters, and volcanoes covered in fine dust and rocks. Fine red dust covers most of the Martian terrain, giving it a similar appearance to the red dust of the Australian Outback. Ingenuity’s vertical lift capability provides an advantage for take-off and landing options; most powered fixed-wing aircraft need a prepared runway to function.
The Martian atmosphere is a thin sheet of mixed gases surrounding the planet and comprises mainly carbon dioxide (95%) and oxygen (1%). Like Earth’s atmosphere, gravity holds the atmosphere to the Martian surface and atmospheric density, pressure, and temperature all decrease with altitude. The air density on the Martian surface is equivalent to about 1% of the air density at the Earth’s surface where conventional helicopters operate. Ingenuity will demonstrate flight in similar flying conditions found in Earth’s upper atmosphere above 100,000 feet. Currently, no helicopter has ever flown above 40,000 feet in Earth’s atmosphere.
Martian gravity is equivalent to about one-third of the gravity on Earth. Ingenuity has a mass of 18 kg on Earth and only weighs the equivalent of 6 kg on Mars. The thinner atmosphere and lower gravity on Mars enable Ingenuity to aerodynamically generate a greater lifting force than would be possible on Earth with the same vertical thrust.
The air temperature at the Martian surface varies between minus 140 degrees Celsius overnight to plus 30 degrees Celsius during the day. The cold temperatures can cause damage to material components, joints, and coupling. Moving parts can also be susceptible to damage from both the freezing cold temperatures and the daily thermal changes as temperatures vary between the minimum and maximum temperature.
Sun-Earth-Mars Integrated Operating Environment
Mars is the fourth planet away from the Sun and the next planet beyond Earth. Newtonian physics describes how the planets orbiting further away from the Sun take longer to complete their orbit around the Sun (i.e. Earth-365 days; Mars 687 Earth days). Consequently, the direction and distance between Earth and Mars are changing non-linearly. The closest point of approach between Earth and Mars is about 62 million kilometres (5-minute radio signal transit), and the maximum separation is about 401 million kilometres (20-minute radio signal transit). The planets’ relative positions are significant for keeping Earth ground station antennas pointing at Mars and realising the transmission time needed for signals to arrive at Mars and vice versa.
The changing relative positions of the Earth ground station on the rotating Earth, a Mars-orbiting communications satellite (i.e. relay station), and the Perseverance rover (i.e. base station) sitting on the surface of a rotating planet, all together complicate the determination of the antenna pointing angles and duty cycles for the workforce on Earth. Moreover, radio blackouts naturally occur when the Mars orbiting relay satellite is either below the Martian horizon and not visible to Perseverance or the satellite is passing over the far side of Mars which blocks its transmissions to Earth.
Additionally, Earth and Mars will occasionally be positioned directly in line but on opposite sides of the Sun when solar flux disrupts radio transmissions, which causes a radio blackout between the two planets for about two weeks. The blackout period requires that mission planners use accurate simulation prediction models of the planetary orbits and planet rotations to precisely determine the antenna pointing angles and predictions of radio blackout periods. A remotely piloted system will need to rely on automation to continue functioning with a planned extended-duration mission or contingency actions when line-of-communication is broken.
Space is a complex environment for understanding natural disruption risks to radio signals travelling between Earth and Mars, up to approximately 401 million kilometres one-way. Significant threats can be attributed to radiation effects from space weather, solar winds, and solar storms that can disrupt radio signals and unprotected electrical systems. Cosmic background radiation noise and unpredictable cosmic radio bursts can also disrupt radio transmissions. It is essential to understand the natural environment to understand the risks to mission activities and correctly attribute causes and effects that may drive better system designs for damage prevention or functional designs for more straightforward repairs and remediation.
An Australian Connection is Critical to Mission Success
Australian technical staff employed by CSIRO operate the NASA Deep Space Network (DSN), during Australian daylight hours, from the NASA Canberra Deep Space Communications Complex (CDSCC) Tidbinbilla. CDSCC Tidbinbilla is one of three ground stations strategically located around the world (i.e. Madrid, Spain; California, USA; Tidbinbilla, Australia) to assure continuous communications links with interplanetary and deep space missions as the Earth rotates.
The DSN must be operated 24/7, requiring the ground crews in each station to transfer the line-of-sight communications link to the next DSN station with Mars in its field-of-view as the Earth rotates. Management responsibility for operating the DSN is also rotated between the three separate DSN crews as the daylight operating hours shift across the globe. Australians operate CDSCC Tidbinbilla, and the DSN under an Australia-US agreed treaty being executed by CSIRO and NASA.
Conclusion
Ingenuity is a remotely piloted rotary aircraft displaced in space and time. NASA uses Ingenuity to innovate ways for using off-the-shelf materials and engineering to develop a helicopter to disrupt the established means and missions traditionally used for interplanetary exploration. The first powered, controlled flight in the air sets a milestone for the first use of air power by humankind on another planet. Reviewing and understanding the details of NASA’s achievements with Ingenuity helps understand design risks for RPAS missions and mission systems on Earth.
About the Author
Squadron Leader Michael Spencer is a Maritime Patrol & Response Officer in the Air Force Reserve. He started his Air Force career as a Navigator in P-3C Orions, conducting long-range maritime patrols. During an extensive and diverse Air Force career, he completed postgraduate studies in space science at the Royal Military College of Canada for duties back in Australia in the Defence Space Coordination Office and Defence acquisitions of ground-based space surveillance systems. Currently, he is employed in the Defence COVID-19 Task Force and the Air Force Remotely Piloted Aircraft Systems (RPAS) Team. He also promotes space interests and opportunities through volunteering with the Space Law Council –Australia & New Zealand and the American Institute for Aeronautics & Astronautics.
This article was first published by Central Blue on April 24, 2021.
For the first of this two part series, see the following: