22 September 2020
An ingenious helicopter on Mars
Source: By Susheela Srinivas: Deccan Herald
Despite a raging pandemic and a last-minute moderate earthquake, there was no stopping Perseverance, NASA’s latest rover to Mars, from taking to the skies. Perched on top of the Atlas V rocket, a rotating disc-like spacecraft shot into space on July 30th, carrying the rover on an interplanetary mission to Mars. Perseverance will travel some 450 million kilometres in a quest to explore signatures of ancient life on our planetary neighbour.
The earlier Mars missions revealed that the now cold and dry red planet has water trails embedded in its rocky terrain. And, where there is water, the possibility of remnants of ancient life forms (even if microscopic) in frozen form is rife. Perseverance is out to check out these biosignatures with the help of advanced machinery that will drill through rocks and collect samples. The samples will be stored safely on Mars for future missions to bring them back to earth.
Apart from these futuristic experiments, Perseverance is also supporting another agenda – delivering a mini-helicopter named Ingenuity to Mars.
Ingenuity is hitching a ride on Perseverance, tucked under its belly. The helicopter is a two-kilo, marvellously crafted machine which took more than three decades to engineer. Like a drone, this experimental machine will conduct an aerial survey of Mars within specified regions. Most importantly, the success of Ingenuity will demonstrate and establish the technology capability to fly an aircraft on another planet. It will open avenues for future missions to utilize comprehensive flying machines on other planets.
Helicopters depend on air to provide an upward lift. For this, their rotor-blades rotate to cut through the air and generate the lift. Mars has a very thin atmosphere on its surface – almost 99 times less dense than that of the earth (a rough comparison would be the available air at an altitude of about 30000 meters on earth). Hence, there is very little air-lift from the Martian atmosphere. To overcome this drawback, Ingenuity is designed with two sets of thin, lightweight, 4 feet long fibre rotor blades.
The blades rotate in opposite directions, five to six times faster (at 2400 rpm) than a traditional chopper rotor to generate the necessary air-lift for the two-kilo drone to be airborne. Moreover, the chopper’s engines have to run overtime to create the air-lift. Once, the lift is achieved, the low gravity of Mars (which is one-third that of the earth) aids it to keep the machine flying.
Second, the lift and landing of the copter on the Martian surface have to be smooth operations without raking a plume of regolith. Regolith is the fine abrasive dust on the surface which can hamper the machinery in no time. Ingenuity will land on four scrawny, padded legs for a smooth landing.
Next, the long nights on Mars can be intensely cold, with temperatures dropping to -90 degrees Celsius and Ingenuity must safeguard itself from these freezing climes. Solar panels fitted above the rotor will recharge the batteries for a whole day, and use two-thirds of it to keep the copter warm.
Despite these measures, Ingenuity cannot be controlled in real-time like a drone by ground-based engineers. Ingenuity is paired to Perseverance for communication. All signals from Ingenuity will go to the rover first, which in turn will beam them to an orbiting spacecraft, from where they will be transmitted to earth. The signals take some time to travel to earth due to the vast interplanetary distances.
To overcome transmission delays, commands are sent in advance. However, for the most part, Ingenuity will make its own navigation decisions. Specially designed software will feed data from the onboard sensors to the chopper. Simultaneously, Ingenuity will continuously stream the real-time data to the rover for transmission to earth.
Besides, Ingenuity must survive the rigours of space travel: a seven-month-long space journey, high gravitational forces and scorching temperatures during descent.
If Ingenuity is successful, it will be a historic endeavour, for, any day, a flying probe is better enabled than ground rovers. Aerial surveys offer the vantage of accessing broad area information and can scan hard to reach areas.