When NASA's Mars 2020 rover touches down on the Red Planet in February 2021, its manifest will contain something never seen before off Earth – a helicopter. The product of over four years of design, redesign, and testing, the Mars Helicopter is a small, autonomous rotorcraft about the size of softball and weighing in at less than 4 lb (1.8 kg). It has the potential to revolutionize the study of other planets by introducing robotic heavier-than-air aerial vehicles to the task of deep space exploration.
The exploration of Mars has come a long way since the first Viking landers successfully touched down in 1976, but there is still a long way to go. Nuclear-powered and solar-powered rovers may have greatly expanded the territory at the disposal of space scientists, but they're still very limited. NASA's Opportunity rover is a long-distance champion by Martian standards, clocking up 25 mi (40 km), but that took it 14 years. The average cyclist on Earth could cover that easily in a couple of hours.
What's worse is that the terrain of Mars is like trying to traverse the Gobi Desert. There are soft sands that can trap wheels; sharp stones that can shred treads; cliffs; gullies; craters; and all manner of obstacles that can separate a rover from some tantalizing scientific discovery. With this in mind, NASA is looking at ways to literally fly over those obstacles using miniature helicopters.
Unfortunately, it isn't a matter of just taking a commercial drone off the shelf and sticking it on a Mars-bound rocket. There are major engineering hurdles to overcome before a technology demonstrator is ready for its interplanetary mission.
"The altitude record for a helicopter flying here on Earth is about 40,000 feet (12,200 m). The atmosphere of Mars is only one percent that of Earth, so when our helicopter is on the Martian surface, it's already at the Earth equivalent of 100,000 feet (30,000 m) up," says Mimi Aung, Mars Helicopter project manager at the Jet Propulsion Laboratory (JPL) in Pasadena, California. "To make it fly at that low atmospheric density, we had to scrutinize everything, make it as light as possible while being as strong and as powerful as it can possibly be."
Under development at JPL since August 2013, the Mars Helicopter uses electrically-driven counter-rotating blades specially designed to handle the thin Martian air thanks to their wide span and rotation of 3,000 rpm, which is 10 times faster than their Earth counterparts. These are powered by lithium-ion batteries charged by solar cells that also help to run heaters to protect the electronics from freezing in the subzero Martian nights.
Mars 2020 is scheduled to launch atop a United Launch Alliance (ULA) Atlas V rocket from Space Launch Complex 41 at Cape Canaveral Air Force Station in Florida in July 2020. When it lands on Mars, the helicopter will be attached to the rover's belly pan. The robotic explorer will use its arm to remove the helicopter and place it on the ground before moving to a safe distance. Mission control will then remotely activate the helicopter's autonomous flight systems. Because it can take up to 23 minutes for a radio signal to travel between Earth and Mars, the helicopter's onboard computer handles all flight operations.
According to NASA, the helicopter will first carry out a series of system checks before attempting its first flight, which will consist of raising itself to an altitude of 10 ft (3 m) and hovering for 30 seconds before returning to solid ground. Eventually, over the course of 30 days, it will make five flights of increasingly farther distances, eventually to heights of up to hundreds of meters and staying in the air for up to 90 seconds. Meanwhile, the rover will act as a data relay.
Because the Mars Helicopter is a ride-along experiment and not central to the Mars 2020 mission, NASA sees this as a high-risk, high-reward project that could pay off high scientific dividends for future missions, but will not adversely affect the present rover mission if it fails.
"The ability to see clearly what lies beyond the next hill is crucial for future explorers," says Thomas Zurbuchen, Associate Administrator for NASA's Science Mission Directorate. "We already have great views of Mars from the surface as well as from orbit. With the added dimension of a bird's-eye view from a 'marscopter,' we can only imagine what future missions will achieve."
The video below shows environmental chamber tests of the Mars Helicopter.
Source: NASA
Alternatively: using reinforced, highly conducting microwires to transmit power isn't a crazy idea. And transmitting a high voltage would allow the use of very long wires weighing virtually nothing.
To propel the craft either the "whip-powered" method or sending electricity to an on-plane electric motor would work - the first probably being preferable because a control-line type plane has to be mechanically launched anyway.