The countdown has begun!
On Monday (Nov 26), NASA’s InSight lander will plunge into the Martian atmosphere at a speed in excess of 12, 000 mph before landing on the planet it has been hurtling towards for the last six and a half months.
In the “seven minutes of terror” separating entry from touch down, the lander has to decelerate from that incomprehensible speed to a speed safe enough for landing without incident
To be able to do that, InSight will first deploy a parachute about three minutes after entry; and drop the heat shield.
The maneuvers will slow it down drastically, which is still not good enough, as three minutes later it will still be far from landing speed, the ground rushing at it at 180 mph.
This is when the lander deploys its tripod legs, gets rid of the back shell and fires the retro rockets, coming to rest on the equatorial plane of Elysium Planitia a minute later – thereby completing the entry, descent, and landing (EDL) sequence.
However, there are so many possibilities of something going wrong – for example, the parachute might fail to deploy; the landing legs could malfunction; the heat shield could fail to jettison or damage the lander as it drops; a surface obstruction could botch the landing; and so on.
“If the lander were to tip over, it doesn’t have the ability to right itself. says Rob Grover of the Jet Propulsion Laboratory in Pasadena, California.
“We would be stuck in that position. The science would be very difficult to do,” he says.
To add to the probable threats is the real one of dust storms; well, it’s that time of the Martian year.
“A global dust storm can blow up in a matter of days,” says Grover matter-of-factly.
“We’ve been rehearsing for that,” he says. “We’ll land successfully in just about any conditions thought possible during the season.”
“If Elysium Planitia were a salad, it would consist of romaine lettuce and kale — no dressing,” InSight principal investigator Bruce Banerdt said in a statement, emphasizing the monotony of the terrain of the landing site.
“If it were an ice cream, it would be vanilla,” he added.
From here on will begin the well-equipped landers science work of providing an InSight into the planet’s seismology and internal temperatures, and more.
But all of that is on paper, for now; come Monday and we’ll know if it translated into success, at least the EDL part of the mission.
Although there have been far more failures than successes when it comes to landing a craft on the Red Planet, NASA can take comfort in the knowledge that most of the failed attempts are dated, with a string of failures taking place in the latter part of the last century, including Mars 96, Mars Observer, Mars Climate Orbiter and Mars Polar Lander missions.
That said, Mars landings involve some of the most complicated and trickiest deep-space maneuvers, requiring “thousands of steps” to complete the EDL sequence.
“Although we’ve done it before, landing on Mars is hard, and this mission is no different,” says Rob Manning, chief engineer at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California.
“It takes thousands of steps to go from the top of the atmosphere to the surface, and each one of them has to work perfectly to be a successful mission,” he says.
Coming back to the entry, descent, and landing phase of the mission, there are three areas of difficulty that makes landing a craft on Mars far more difficult than say a moon landing; one is distance and the other two are related to the Martian atmosphere.
Mars is way too far away for direct human intervention in a landing sequence; in fact, so far away that by the time a signal is received and responded to, the end result you’re trying to influence will have already happened – one way or another.
When a spacecraft is returning back to earth, the heat shield protects it from burning up from the friction of entry, while the same friction helps in slowing down the craft until a parachute can take over for the rest of the way down.
Although the Martian atmosphere is thick enough to make a heat shield necessary, it is too sparse for a parachute to do the job alone; hence, the need for retro rockets to slow the descent down to landing speed.
Another area of concern for a Mars lander is the erratic horizontal velocity caused by the Martian winds, which can be as unpredictable.
Moon offers no such worries, as there is no atmosphere to burn a lander and no air to check a parachutes descent.
All that you need to do is point some rockets downwards to offset the velocity with reverse thrust from the inverted rockets.
Interior Exploration using Seismic Investigations, Geodesy and Heat Transport, better known as InSight, was launched aboard a United Launch Alliance Atlas V rocket on May 5, 2018.
Also on board were two experimental CubeSats, MarCO-A and MarCO-B, aimed at testing their capability in interplanetary space.
The two MarCOs are also expected to keep an eye out for InSight and beam back the lander’s data as it attempts the landing next week.
Although launched with the lander, they are flying separately to Mars and will not attempt to land – that’s for the InSights of the world to worry about – but will instead do a flyby of the Red Planet and wait for their short operational lives to end.