NASA’s Perseverance rover is set to land on Mars today around 9pm Irish time, which, if successful, will be the 5th man-made rover to land on the red planet. But there’s still lots that could go wrong.
Now, as the rover’s 7 month-long journey through space comes to an end, it will finally make contact with the Martian atmosphere at blistering speeds of around 20,000 kilometers per hour, at which point its “EDL” process will begin – Entry, Descent and Landing.
This is the point that NASA scientists call the “7 minutes of terror”, as it takes 7 minutes for the craft to touchdown on the Martian surface, and there is a high likelihood of things going horribly wrong. It can take as long as 24 minutes to send a message to Mars (depending on where on the Red planet you want to communicate), and this means that if scientists on earth detect some disastrous error, by the time the problem is spotted and a new order is sent, it will likely already be far too late to fix. This means the entire landing process will be more or less autonomous, and it’s up to the machine’s programming to adapt to unforeseen variables.
“This is one of the most difficult maneuvers that we do in this business, and almost 50% of the spacecraft that had been sent to the surface of Mars have failed,” said Matt Wallace, the mission’s deputy project manager.
Touchdown on the narrow Jezero Crater is set to take place around 8.55pm GMT, and weather conditions in the area appear to be favourable.
Ten minutes before entering Mars’ atmosphere, the craft will shed its cruise stage rockets that had sustained it throughout the journey, leaving only a protective shell containing the rover and the rockets to help slow its descent.
At this point it will ensure that its heat shield is facing towards the planet, so as not to burn up on reentry – temperatures on this shield can reach highs of 1,300 degrees centigrade. Meanwhile, all going according to plan, the rover inside will be untouched by the blistering temperatures due to the aeroshell capsule that surrounds it.
It is possible that the craft will hit air pockets which will throw it off course, but this is to be expected – NASA have included thrusts which it can use to correct its course on the way down.
Once the craft has slowed to around 1,600 kilometers per hour (remember, it was previously travelling at 20,000) – it will deploy a 21.5 meter wide supersonic parachute 11km up, with a new technology called “Range Trigger” detecting the perfect moment to pull the chute. According to the head of NASA’s EDL process, Allen Chen, this is the biggest area of risk during the whole 7 minute process.
After deploying the parachute, the craft will drop its heat shield, and will use radar to detect its precise altitude above the Martian surface. Using the Terrain Relative Navigation system, the rover will then be able to compare what its seeing to an onboard pre-programmed map with a selection of safe landing sites.
Because Mars has such a thin atmosphere, the parachute will not work as effectively as it would on Earth however. The parachute will only slow the vehicle down to 300 kilometers per hour – much slower than the initial 20,000, but still fast enough to obliterate the craft on impact. At this point, the craft will have to cute the chute, and use rocket thrusters to slowly lower it to the ground as safely and carefully as possible using an eight-engine jetpack around 2 kilometers up from the surface.
Once 20 metres above the ground, the rocket will lower the Perseverance rover gently to the grund using cables, in a complex maneuver called “skycrane”.
At this point, the rover will make contact with Mars’ surface at speeds of a little over 1 kilometer per hour, and will be ready to begin its mission into the great beyond.
It is the first rover mission designed to seek signs of past microbial life. Earlier rovers first focused on and confirmed that Mars once had habitable conditions, and this one may finally give us some insight into whether or not we are alone in the universe. It also seeks to examine the Martian climate, geology, and prepare the way for potential future Martian colonies manned by permanent human settlers.