On July 30th 2020, a United Launch Alliance Atlas V rocket lifted off from Cape Canaveral,
Florida. Carrying the next generation of Mars Exploration Vehicles.The Perverence Rover
and the Ingenuity Helicopter.
And, today, on February 18th 2021, if all goes to plan, the two vehicles will land
safely on the Martian surface after their long 7 month journey to the Red Planet.
Only about 40 percent of missions sent to Mars have been successful
and perseverance will have to endure a vicious and complicated landing sequence,
as it’s creators wait, powerless to intervene, waiting for news of its success back in Pasadena.
Perseverance rover is the largest and heaviest rover JPL has ever sent to Mars. Heavier than the
Curiosity Rover by 100 kilograms, and with that extra weight comes a whole host of new gadgets.
This isn’t just some slightly upgraded version of the curiosity rover. Perseverance is
benefiting from almost 10 years of advancement of technology. It’s packed with fascinating and
novel technologies that will form a stepping stone in humankind's eventually first steps
on the surface of the red planet. This is the insane engineering of the Perseverance Rover.
Perseverance, hopefully, is now safely on the ground
where it will live a long illustrious life on the red planet.
We have learned some things from the Curiosity Rover that will hopefully
help Perseverance avoid the struggles it’s predecessor is experiencing.
We have made an entire video on the struggles of the Curiosity Rover wheels and how they
have been gradually falling about on the harsh Martian service. In the end the engineers at JPL
did not opt for shape memory alloy wheels like the ones we discussed in that video,
but simply increased the diameter of the wheels, decreased their width and increased the thickness,
while incorporating sturdier curved threads that will better resist crack growth than
Curiosity’s sharp cornered threads. [1] They have also forgone the rectangular cut outs which
imprinted morse code, spelling out the Rover’s origins, in the rusty dirt of its new home.
There is a whole host of new software upgrades too. Like the algorithm that determines when
to open the parachute. In the last mission the parachute simply deployed when the target speed of
1450 kilometres per hour was reached, after most of the hypersonic re-entry speed of
21,450 kilometres per hour had been bled off. [2]
For perseverance, JPL wanted to increase the accuracy of their landing, so this time around
the chute will open when it is approaching the optimal trajectory for the landing site.
It will also be scanning the surface of the landing site and correlating those images to
it’s pre-existing map to allow the skycrane to choose the best landing site with minimal
obstacles. Perseverance’s ground navigation systems have also been significantly upgraded,
with it’s optical sensors feeding data to a machine learning vision algorithm.
Allowing Perseverance to find it’s own path through the rough terrain of Mars,
where Curiosity had to constantly stop and start with help from it’s earthbound controllers.
Perseverance is benefiting massively from the past decade of improvements
in autonomous flight and driving developed by the drone and automotive industries.
This will mean Perseverance will be able cover much more ground during its life,
here, in Jezero Crater [3]. A massive crater that was once home to a lake the same size
as Lake Tahoe. You can see the remnants of this ancient river bed
and delta spilling into what may have once been a habitable body of water.
It is here that Perseverance will scour for signs of life. Before we get into all the
gadgets it will use to do this, let’s look at how Perseverance will power them. The
Perseverance Rover features the same Radioisotope Thermoelectric Generator as the Curiosity Rover.
RTG’s work by converting the heat from the natural decay of a radioisotope into electricity.
It uses a simple principle called the Seebeck Effect to generate electricity.
[4]The seebeck effect essentially allows us to generate an electric current
through a heat differential, as charge carriers, both electrons and electron holes,
will move from hot to cold. So if we have two semiconductors,
one with charge carriers in the form of electrons and one with charge carriers in the form of holes.
A potential difference between the two semiconductors will form when a heat
gradient is applied. This potential difference causes a current to flow in the external circuit
These two semiconductors need to be both thermally insulating, to ensure this heat gradient
is maximized, but also electrically conductive to maximize the current. These two material
properties are typically linked. Copper is both a great electric and heat conductor,
while iron is a poor electric and heat conductor. Having a single material that is a great electric
conductor and a poor heat conductor is extremely rare. For this reason two unique materials are
used for the p and n type semiconductors. Lead Telluride for the n-type and an alloy commonly
called Tags for the p-type, which is formed from tellurium, silver, germanium and antimony. [4]
Now we just need a consistent heat source. Thankfully
radioactive substances generate heat as they decay.
The perseverance rover RTG uses 4.8 kilograms of plutonium dioxide as it’s heat
source. This radioactive material primarily produces alpha waves, which is essential,
as this form of radiation is most efficiently converted to heat in a compact space. [5] [6]
While Plutonium 238 also releases minimal beta and gamma radiation,
decreasing the weight of shielding needed to protect the electronics onboard from these more
powerful kinds of ionizing radiation, an essential characteristic for a lightweight spacecraft.
The Plutonium 238 is also formable into a ceramic like material that will break into large chunks,
rather than being vaporised and spread in the wind during a launch failure, where it could be inhaled
or introduced into the food chain. [7] [8]
The electricity this unit can provide will gradually degrade,
from it’s maximum of 110 watts at launch, as its plutonium heart naturally decays.
Losing half of its energy every 87.9 years, which is much longer than the 138 day half life of the
early polonium 210 RTG prototypes. [8] Another advantage of Plutonium 238 for this application.
This will power all the instruments onboard,
like the Moxie instrument, which is one of the new devices I am
most excited about aboard Perseverance. Moxie is a new oxygen generation device
that will test a vital technology for any future human mission to Mars.
You may wonder, like I did, how is this different from the oxygen generation present
in the international space station. There is obviously a limited supply of oxygen there.
Why do we need to test this new technology on Mars,
when we obviously have a tried and tested method of creating oxygen already. Surely?
The international space station does not really recycle oxygen. Oxygen is created
on the international space station through the electrolysis of water. [9] This produces
hydrogen and oxygen. The hydrogen is then reacted with carbon dioxide to form water and methane.
The methane is then simply exhausted into space while the water is fed back into the system.
The international space station requires regular resupply of water
as we are losing 2 hydrogen atoms for every oxygen molecule we create.
This is not a closed loop system and water is a pretty heavy material to be shipping to Mars.
The perseverance rover will test a new method of oxygen creation
using this device which will use solid oxide electrolysis to instead break
the plentiful carbon dioxide in the Martian atmosphere into Oxygen and Carbon Monoxide.
It’s operation is fairly simple. Air will be taken in through a dust filter by a specialized pump
designed to be as light and compact as possible called a scroll pump. [10] Scroll pumps are
pretty cool. They consist of two spiral scrolls, one stationary and one rotating. Air is taken
in at the inlet here and as the secondary scroll rotates in traps and squeezes air
against the primary stationary scroll. This continues to happen as the volume between the
two scrolls decreases down the spiral, causing an increase in pressure, in this case it takes the
variable pressure Martian air, which is typically about 100 times lower than earth's atmosphere,
and compresses it to match earth's sea level pressure. These kinds of pumps are lightweight,
energy efficient and reliable. Making them the perfect air pump for the Perseverance Rover.
The pump feeds the carbon dioxide rich air through a cell stack. Each stack consists of
a catalytic cathode, a solid electrolyte, and an anode. [10] As air passes over the cathode,
which operates at 800 degrees celsius, the Carbon Dioxide is split into carbon monoxide
and oxygen ions, according to this reaction. The oxygen ion passes through the solid electrolyte
to the anode where it is oxidized, combining with a second oxygen atom,
to form gaseous O2, which is then passed out of the anode cavity and tested for purity.
Animation Extra 1 Potential 3D Render of the unit on table
top here, but there is footage of the device: Moxie can produce 20 grams of oxygen an
hour. However the unit will not run continuously,
as it draws too much electricity, which will be needed for other operations.
B-Roll Highlight RTG, Moxie and Batteries. Not sure where batteries are located
In total the system needs 168 watts,
which is actually more than the 110 watts the RTG can provide at any one moment,
so this operation will need to be supplemented by the two lithium ion batteries that are included on
board to make up for the low power RTG, allowing it to store excess power during down time.[11]
This device is exciting, because this is a clear statement of intent.
Oxygen is going to be a vital resource for any future human missions. And , this is actually
a scaled down prototype of the full sized version NASA eventually wants to send to mars, along with
an empty rocket. The full scale version will produce about 2 kilograms per hour, which will
gradually be stored inside the awaiting rocket over the course of a year and a half, providing
life sustaining air for any future human missions and the oxidizer needed for the ride home. [12]
The next device, which is also depending on a future Mars mission to complete its purpose,
is the core sampling drill. The curiosity rover sampling system drilled and scooped soil into this
instrument, the SAM, standing for Sample Analysis at Mars. The SAM is located here on the rover.
It contained multiple tools that would be commonplace
in many earth bound labs. A mass spectrometer, a gas chromatograph
and a tunable laser spectrometer. Each looking for different signs of life on Mars.
Perseverance has replaced the space this unit took up with a totally new system.
The Sample Caching System. The robotic arm of the rover features a coring drill which will
cut out cylindrical core samples from the Martian surface. Once collected the robot head mates with
the drill bit carousel where it transfers the bit and the sample tube into a rotating carousel
that takes it to the belly of the rover where another robotic arm resides.
Here a number of operations takes place. First the arm pulls the sample tube out of
the drill bit and takes multiple images of it before and after calculating the volume of the
sample. [13] Then it stores it in one of the 42 slots under the belly of the rover, where they
will remain until the rover deposits them in these sample tubes at a designated caching
spot on the surface of Mars. This is where things get really interesting.
There are plans to send another rover, designed by the ESA, to Mars in 2026. [14] This rover will
deliver the samples back to it’s NASA designed lander which will load them into a mars ascent
vehicle. Blasting the samples into orbit, where an ESA Earth Return Vehicle will be waiting for it.
We are attempting to bring soil back
from Mars….with robots. If that isn’t insane engineering I don’t know what is,
and we have barely scratched the surface of what this rover is capable of.
There is a whole host of new sensors on board that do not require Perseverance to collect soil.
Each using different forms of electromagnetic radiation to investigate the ground below them.
The SHERLOC instrument on the robotic head will look for signs of biosignatures using Raman and
Luminescence spectroscopy, which both detect molecules based on how they interact with UV
light. [15] It will sit about 5 centimetres off the ground where it will focus it’s UV laser
onto the soil and be able to detect chemicals that would indicate the presence of past life.
The Rover also has an x-ray imager can PIXL that will be able to visualise the texture of the
ground below it looking for tiny variations in geology that would indicate that microbial life
has altered the environment, [16] while also being able to detect chemical compositions by
observing the fluorescence of the target under x-ray electromagnetic radiation.
There are several other sensors, like the ground penetrating Radar imager
located at the rear of the rover, which will give us visualizations of the composition of geology
up to 10 metres under the surface, and possibly even identify water
resources buried below. [17] A vital resource for future human missions.
These are just some of the sensors aboard and of course there are the usual high definition
colour cameras that are going to send back amazing images to earth
and we included a microphone, so we will be able to hear what our future life on Mars
may sound like.It may even catch the whirring of helicopter blades off in the distance.
Because, by far the most exciting part of this mission,
to me, is the ingenuity helicopter. After all, if successful, this will be
the first time humans will have demonstrated controlled powered flight on another planet.
Powered flight on Mars presents many challenges. The atmosphere is about 1% the density of Earth’s,
meaning there is less air to push down to achieve lift. To combat this the propellor
blades, which are counter rotating to eliminate the need for a tail rotor,
spin much faster than a traditional helicopter blade at about 2400 RPM. [18] That’s about 5
times faster than an equal sized RC helicopter here on earth. To deal with the centrifugal
forces that come with that the blades need to be made of high strength carbon composites.
These blades also have a much larger angle of attack than your run of the mill blade,
allowing them to push a larger volume of air downwards.
Since this helicopter will detach from the Perseverance rover, it needs its own power
source too. Unlike the planned Dragonfly mission to Titan, this helicopter will not have it’s own
RTG. Creating an RTG capable of fitting into this tiny 2 kilogram helicopter is unfeasible.
Instead it features these solar panels, which will charge 6 lithium ion batteries on board
and these in turn will power the motors and cameras aboard.
For a max flight time of about 90 seconds. This is simply a technology demonstration that will
hopefully give NASA and JPL the information they need to approve and design a future flying rover.
Today, the 18th of February is a historic day that I
and many others will remember fondly for years to come.
I remember exactly where I was and what I was doing when the Curiosity Rover landed and I
remember seeing this man on my screen. A man who subverted my vision of what an engineer working
on something this advanced was supposed to look like. Bobak Ferdowsi. I could see myself being in
his seat. He was relatable, not the white shirt, black tie, nerdy figure I had grown up expecting.
I remember because I was a fresh college graduate, struggling to find a job, at a music festival
begging the organisers to put the landing on the big screens, but just ended up watching the
livestream on my phone in a tent that was falling apart. I didn’t fit the stereotype either. Today,
on the historic landing of Curiosity’s younger brother, I released an interview on Nebula with
that man that I now somehow call a friend. Talking about his career path into JPL and what it was
like becoming famous literally overnight. That interview is now available ad free on Nebula.
Along with a whole host of new original content not available
anywhere else. Mustard’s new original called “The Origins of Stealth”, which details the
fascinating history of the F-117 Nighthawk. A 3 part trivia game show made by Sam from Wendover,
and featuring yours truly, that really shows how distractible and unserious I am in person. These
videos don’t get my personality across at all. And ofcourse my 9 part logistics of d-day series.
We are constantly adding more original content and ad free versions of our YouTube videos,
and all of that comes bundled with CuriosityStream for the low price of just 14.79 a year.
A little over 1 dollar a month. This is by far the best way to support this channel
and get something in return with all the amazing award documentaries on CuriosityStream,
like this fascinating biography of Neil Armstrong’s life,
narrated by Harrison Ford. And you get access to all our Original content on Nebula.
If you are looking for something else to watch right now,
why not watch my previous video about NASA’s weird and wonderful
oblique wing plane,, or Real Science’s latest video about the insane biology of ant colonies.