NASA's Perseverance rover will attempt to land on Mars this week | Hacker News Reader

NASA's Perseverance rover will attempt to land on Mars this week

spectrum.ieee.org

300 pointsquercusa105 comments

Mark Rober has an awesome video on this which outlines a lot and gives a very high level bit of info on it. I can't imagine the amount of stress these engineers are feeling watching this delayed feed.

https://www.youtube.com/watch?v=tH2tKigOPBU

I wonder how many of those engineers have woken up, wild eyed in the middle of the night, as their brain excavates some random issue or loose end that surfaced and silently trailed off years ago, never to be properly resolved before launch.

It’s happened. Worst one I’ve heard of is when an engineer got an idea of how things could go south just days before the final decision point, ran to the testbed, tried it out, and their worst fears were proven right. They took it to the team, and after much wailing and gnashing of teeth, everyone collectively decided they were more confident in the level-headed plans they had executed to validate the system over the past 5+ years than this last minute, panic-induced test. So...they decided to let the sequence run as planned, and loaded up on a double helping of peanuts for the big day.

Well, the big day comes and guess what? The spacecraft performs perfectly. Everyone was absolutely ecstatic.

It turns out the test bed had been misconfigured, and there was nothing wrong whatsoever with the spacecraft or any of its command sequences.

Really makes you think about how to make the best possible decisions in a crisis.

This is fascinating. Do you have a link with more info?

This would make an amazing blog post.

What's the lesson in that story? I would have thought that you'd postpone until having fixed the problem exposed by that last test.

This is only really a viable option prior to launch, of if the probe is coasting and you have enough time.

If the probe is already near its destination, you have a very narrow window during which you can adjust its velocity for intercept.

If you delay too long you do not have enough deltaV to intercept, and either miss your target entirely, or end up in the wrong final orbit with no ability to correct your inclination or eccentricity to what your mission parameters call for. Then you've basically spent years to send a paperweight to Mars.

If the issue requires physically accessing the payload (which has been prepared and packaged, and is sitting on top of a huge rocket) it's not always that easy.

The minimum-energy launch window occurs every 2 years, and lasts a couple of weeks.

I've had microscopic renditions of this kind of thing in my career. There's a cognitive 'dolly zoom' effect where there's an illusion of growth in a given risk because the field of view has been narrowed by the preconditions and/or assumptions that led you to consider it to begin with.

It's like the risk of losing a winning lottery ticket. Broadly the risk is negligible, but when you zoom into the precondition of having won the lottery, it's a big fucking deal.

The Cassini–Huygens mission had exactly such a moment [1,2]. A year or so after it was lunched somebody pointed out that Huygens and Cassini communication may fail due to a flaw in handling of Doppler shifted radio signals on Cassini, which should relay data from Huygens. Luckly the spacecraft used a Venus gravity assist and had a close encounter with Earth again, so the issue was tested and confirmed. Engineers had to adjust the descent profile of Huygens, releasing it earlier than originally planned. This made its batteries last shorter after landing on Titan, but the whole mission was saved and data from the surface was properly relayed to Earth.

1. https://en.m.wikipedia.org/wiki/Huygens_(spacecraft)

2. https://youtube.com/watch?v=3ubr151wrHQ

The progress from "we can hit a region and maybe last a year" circa the Spirit/Opportunity era to the current state of "if we don't hit it we're close enough to drive to it" has been amazing.

Better computing resources, better simulations, better materials, better and cheaper process control have enabled engineers throughout the entire supply chain to do more with less and when you take snapshots of progress at multi year intervals like NASA does with its Mars missions the progress really shows.

Oh, in Spirit's/Opportunity's case, that was 90 days (if memory serves me). So, they were successful beyond the wildest dreams. Curiosity, too.

They knew they would last more than 90 days. 90 was just the number they picked for the "days before we can declare success" threshold. They weren't counting on 10yr.

TIL the pacel pirate bomb marker guy worked at JPL for 9yrs. That's a really interesting career trajectory.

That's how NASA funding pays off!

dude mentions it every chance he gets...

As he should. Nasa is cool.

I understand the dude needs to sell himself, but "hey I'm _____ and I worked at NASA!" isn't really that different from "hey I'm _____ and I went to Harvard!"

I don't care. He is selling Nasa as much as he is himself.

Maybe not to you, but to me (and I think others) it is quite different. And he gets people excited about science and NASA that way too.

That is it. Why I don't care. He's doing good advocacy.

I kinda wonder why he left.

Same. I am sure he has good reasons. Might just be playful ones.

I avoid those "made for youtube" type channels with a bunch of kitschy experiments. I was just surprised he has a legit resume.

You should watch the squirrel video!

This video goes into much better detail on the science experiments loaded up on the river. https://youtu.be/95hMM2u6Fgw

For some more technical details: https://www.youtube.com/watch?v=W0NakShgbHY. This makes me even more anxious, there are just so much things that have to go right.

I work in aerospace, one of my colleagues is part of the team for one of the instruments on the rover. Tomorrow we will attend a NASA telecon with our new mission t-shirts :)

I asked him if he was stressed, his exact reply: "nah not really, not a whole lot we can do now"

> The target is the bottom of Jezero crater, a 50km-diameter impact crater on the northwestern edge of a much larger impact basin called Isidis. In Slavic languages, “Jezero” means lake. Jezero was chosen because it looks (based on orbital imagery) like it was likely a huge lake in the ancient past, with rivers running into it and forming river deltas like we have here on Earth.

I mean, yeah, Jezero means lake, but the crater was named specifically after a municipality in Bosnia with about a thousand inhabitants (https://en.wikipedia.org/wiki/Jezero,_Bosnia_and_Herzegovina). IIRC it's something about promoting space exploration in more rural towns and villages around the world.

https://planetarynames.wr.usgs.gov/Feature/14300

For a Slav, it is very unusual to see any Slavic word in a worldwide context.

The roots of pretty much everything seem to be Greek, Latin, English, French, sometimes German and Spanish. Seeing anything in an English text that I can actually understand natively in my head (such as Jezero) is a weird system interrupt.

The only possible exception is robot, which does not sound very Slavic on its own. "Robot" does not provoke this interrupt.

It can be both. Jezero was named Jezero because it's next to the jezero.

Edit: Same as e.g. Volgograd (wet town), which is next to the Volga river, named Volga because it's wet.

Martian craters are typically named after towns around the world that have fewer than 100,000 residents to avoid political pressures.

For anyone who has ever looked at the code for betaflight, arducopter or px4 and built a moderately complex quadcopter from parts... I really wonder what the balancing/descent/sensor package and software looks like on the rocket-crane thing.

As I understand it, after it jettisons the aero shell, it reaches a certain height by radar altimeter and then activates active rocket thrust to balance a big square flying platform over the landing area, with a very limited flight time possible (based on weight budget/fuel supplies), and then uses the skycrane system to lower the rover.

What sort of 6-axis IMUs and sensors must be on that thing , and how quickly can it adjust thrust per corner to keep itself flying level while descending...

https://www.space.com/16889-mars-rover-curiosity-sky-crane-l...

Does it swivel the small rocket motors? Or is it based on thrust adjustment only? How many different radar and laser altimeter type sensors does it use to determine that it's above a suitable flat spot? All sorts of fun questions.

Based on available renderings for both skycranes[1][2], the motors do not appear to have any gimble ability, so must be controlled by thrust alone. It's interesting that the valves consume 168 watts of power each, 1.34kw of power just for the throttle valves. The paper in [4] mentions they were adapted from the same engines used for the Viking landers.

A paper specifically on the EDL system [4]. Page 13 is where the fun starts. The IMU appears to be a Honeywell MIMU [5][6] and is combined with a radar altimeter for navigation and attitude control.

Datasheet for the motor [3] (Pg. 13)

[1] https://planetary.s3.amazonaws.com/web/assets/pictures/curio...

[2] https://www.youtube.com/watch?t=569&v=obzGkiyelt8

[3] https://www.rocket.com/sites/default/files/documents/Capabil...

[4] https://trs.jpl.nasa.gov/bitstream/handle/2014/44894/13-0633...

[5] https://aerospace.honeywell.com/en/learn/about-us/customer-s...

[6] https://satcatalog.com/component/mimu/

Almost more significant than the new Perseverance mission is the old Curiosity mission (https://mars.nasa.gov/msl/mission-updates/) which has been operating for 3,034 (Earth) days since its landing on August 6, 2012. (Technically it's been 3,116 days since the landing, but Nasa reports the smaller number, perhaps because of some downtime.)

One can only imagine the internal debates and budgetary fights around a new rover mission to Mars while a team is still actively operating a very successful and healthy existing rover. Luckily, this new mission did get the green light.

One also might speculate, amidst these multi-trillion dollar "stimulus" bills, what lost opportunities (no pun intended) there have been, had Nasa been budgeted more than its puny $22.6 billion allotment (as of 2020, 5% up from the previous fiscal year).

I can hardly imagine a better investment in the future of the country, the future of science, and the future of humankind, than to explore the Solar System and develop the necessary technologies to enable humans to move off-planet in large numbers.

I imagine it's similar to the LHC where an expensive project over decades breeds a lot of new technology and techniques (if you imagine the statistical equipment required to condense hundreds of petabytes of data over multiple years down to about 100 points on a graph, let alone building CMS and ATLAS).

The 3,034 days refers to how many sols (Martian days) it has lasted. The discrepancy is due to the fact that a Martian day is roughly 24 hours 40 minutes long. That extra 40 minutes over roughly 3000 days leads to the 82 day difference.

Ah you're right, they did say Solar days.

Opportunity had been driving around Mars since 2004 when Curiosity landed.

When NASA does their typical "get kids interested in science" outreach programs the kids they talk to have lived their whole lives with something driving around Mard.

> had Nasa been budgeted more than its puny $22.6 billion allotment

$22,600,000,000.00 yearly income is not puny by anyone’s definition.

It's 0.0471% of the 2020 federal budget, which was 4.79 trillion dollars. That's a pretty puny share of the budget. For comparison, the government gave 45 billion to farmers in 2020[1].

[1] https://www.npr.org/2020/12/30/949329557/farmers-got-a-gover...

> It's 0.0471% of the 2020 federal budget, which was 4.79 trillion dollars

Its just under 1/200, not 1/2000. That is 0.47%. But almost 2/3 of the federal budget is non-discretionary, NASA claims 1.1% of the federal discretionary budget while having 0.8% of the employees. But you’re right, one man’s puny is another man’s puissant and its entirely possible for people to think 20 billion dollars a year is a piddling sum.

There's also a good argument to be made that the research NASA is doing is valuable and reaps generous economic dividends down the road.

> I can hardly imagine a better investment in the future of the country, the future of science, and the future of humankind, than to explore the Solar System and develop the necessary technologies to enable humans to move off-planet in large numbers.

If space exploration is so importanr to the future of humankind, why do Americans have to bear all the expense?

A “puny” $22.6bn buys a lot of food and houses a lot of homeless people.

>If space exploration is so importanr to the future of humankind, why do Americans have to bear all the expense?

Countries other than the United States are actively exploring the solar system, and until recently the United States had no independent capability for manned space flight and depended on Russia's Soyuz program.

To claim that Americans bear all the cost is disingenuous at best.

> why do Americans have to bear all the expense?

Good news: This very month, orbiters from the United Arab Emirates and China both reached Mars. And the latter even has an (as-yet-undeployed) lander.

Good. Let them pay for it. The usa has funded a disproportionate amount of space travel since the 1960s, money which in the end really goes to the military industrial complex.

Other than the fact that there are multiple countries that have space programs.

> A “puny” $22.6bn buys a lot of food and houses a lot of homeless people.

This is reductive line of thinking. You can't equate spending on cutting edge research with taking away from welfare. Earth has finite resources and you need to be forward looking as well while taking care of the present.

Also, it is not like all the research benefits just space exploration or MIC. For instance, research into hydroponics is being used on earth now to grow food with much less resources.

When 99% of the realized benefits are financial windfalls to arms manufacturers, is that 1% really so special?

Americans happily spend excessively on war without blinking yet any suggestion that we devote resources to the welfare of our fellow human being is written off as “godless communism”.

We are in the middle of the worst homelesseness, unemployment and food instability since the great depression. Why is that not of greater importance?

A significant percentage of HN are randian free market fetishists. I say if space exploration has value then let the capitalists fund it, not the taxpayers.

Yes, but it all depends on many other things. For example, you can't have good science without good education, stable political system, and economy. So you need to invest in many other things while you have limited budget. Not just Solar System is important: we're waiting for a launch of James Webb Space Telescope like 15 years now.

My brother-in-law and two friends of mine played a big part in the assembly of the rover - I am so stoked for them to finally see it in action.

Wow, please tell us more. What did they work on? Are those technologies ITAR restricted?

skycrane :D

Is it your siblings spouse or your spouses sibling?

Company training tells me you are phishing

I’ll bet they worked with my friend who is the Deputy Surface Mission Manager for the rover. He gave us a little presentation of what he worked on, including the little helicopter that is attached to the underside of the rover. Veritasium did a cool video about it a couple years ago. [1]

Kudos to everyone who worked on the project and got it launched during the pandemic!

[1] https://youtu.be/GhsZUZmJvaM

The helicopter is the thing I am MOST excited about!

So everyone says the helicopter would be the first powered flight on another planet.

Wouldn't the Skycrane be considered powered flight?

I suppose you could qualify it as first powered flight using aerodynamic forces for lift. Or first powered flight of a probe, the sky crane isn't a scientific instrument.

>And for the first time, Perseverance will be taking along a couple of microphones so that we can hear what Mars sounds like.

This isn't the first time NASA sent a mic to Mars, but it may be the first time that it works.

I'm super eager to hear if the small helicopter manages stable, repeatable flight.

They know exactly what the air density and gravity is and tested for the exact conditions. It it makes to the surface in one piece it will fly.

I realize they're very smart and very thorough, but this sounds an awful lot like "I ran the test suite - if you can apply the patch in production it'll work".

Luckily physics works pretty well.

Unfortunately, everything is trivial in theory.

Isn't Mars known for extreme winds and dust storms, which seem like quite the challenge for an ultralight drone resting on the surface, let alone flying autonomously?

Since the atmosphere of Mars is 1% the pressure of Earth's, even very high velocity wind would have little energy behind it.

Wind forces are defined by dynamic pressure q, which is proportional to speed squared divided by density. At 1% the Earth's air density, a 100m/s wind on Mars (half the speed of sound!) exerts the same force as 10m/s breeze on Earth.

So far the fastest winds observed on Mars are about 30m/s.

So, the thin air that makes it hard to fly on Mars makes it safe to stay on the ground.

Doesn't the suspended dust carried in these wind storms need to be taken into consideration? I presume they contribute significantly to the density.

It's said that during dust storms Martian air carries some 100-1000 dust particles of 1-10um per cm^3.

Running the worst case numbers, 1000 10um particles per cm^3 adds up to about 1/3 the air density. Realistically it's maybe 10% of density increase.

I remember from my flying days that:

“The addition of water vapor to air (making the air humid) reduces the density of the air, which may at first appear counter-intuitive. This occurs because the molar mass of water (18 g/mol) is less than the molar mass of dry air.”

(Not sure I like the language above but that’s how Wikipedia says it)

Is this potential effect accounted for in your numbers? I.e. What happens to the molar mass of Martian atmosphere when Martian dust is suspended in it?

At any rate, dust is bad for the moving parts of flying machines.

This is about gaseous water, not water droplets. Water droplets (fog) increase density (again, not by much).

Dust doesn't have a meaningful vapour pressure and can't influence air density this way.

10m/s is a pretty fresh breeze.

Simulating Martian air density is trivial, just build a vacuum chamber, remove the air, add some CO2 up to the right pressure. But simulating less gravity is incredibly hard:

Tethers are cheap but don't really allow free flight. Parabolic flights only give you a few seconds in fairly cramped space, and getting the low air density inside a plane sounds tough. A large spinning laboratory in space that can be spun up to simulate the desired gravity would be a solution, but we don't have that.

Why would it be complicated though? Is gravity changing a lot? I thought it was just a constant you plug into equations. Air density on the other hand I would think can change for hundred different reasons from one second to the next.

In context the comment is about simulating the conditions physically, hence discussion of vacuum chambers and aircraft.

For the moon practice lander they used a rocket that always pointed down to cancel out enough of Earths gravity to match the Moons gravity. Neil Armstrong seemed to like it :D

They could do something like that.

Neil Armstrong seemed to like it :D

It nearly killed him. I don't think anyone actually liked it, and I bet a lot of people in risk assessment went hard on the "nixon needs to prepare the death letter" story.

> used a rocket that always pointed down

Nit: the Lunar Lander Research Vehicle actually used a CF700 turbofan[0], not a rocket, to partially counter-act gravity.

[0] https://en.wikipedia.org/wiki/General_Electric_CF700

Remove most of the batteries to reduce the weight? Trading flight time obviously. Of course since Martian gravity is only ~.4G, you'd have to remove a lot of weight, so a lot of batteries. On a device that's already been designed to be as light as possible.

Unfortunately, changing weight of the helicopter changes also changes inertia and the moment of inertia [1]. On mars, only the gravitational force changes, while inertia stays the same.

That will be somewhat more tricky (or impossible) to emulate on earth.

[1] https://en.wikipedia.org/wiki/Moment_of_inertia

They still used a tether.

https://www.youtube.com/watch?v=GhsZUZmJvaM

Links to NASA's official live streams:

https://www.youtube.com/watch?v=gm0b_ijaYMQ

https://www.youtube.com/watch?v=GIooAx_GkJs

Sending a probe in the direction of Mars is one thing, but the landing procedure is just mind boggling. Wonder how they simulate the stress and mars environment. I also noted that there will be a drone and HD video from many cameras.

Combining modelling for even simple experiments is a pain so I can't even imagine - even if the end result is "simple" - the amount of book-to-forehead contact required for a rover.

Will there be something to watch live as it lands? What should I expect?

They'll have a stream on NASA TV. Not so many camera feeds as a SpaceX rocket, but I'm guessing similar to this: https://www.youtube.com/watch?v=LAL4F6IWC-Y

Space.com says NASA's landing broadcast will start at 2:15 PM EST on Thursday: https://www.space.com/mars-rover-perseverance-landing-webcas...

There's already some Perseverance stuff being broadcast today, I tuned in for a while earlier and they were answering questions from social media about stuff like the team working on Mars time after landing.

The coverage for Perseverance will actually have seven cameras for landing!

https://mars.nasa.gov/mars2020/spacecraft/rover/cameras/

To ensure it's clear for other readers, footage from the new cameras will not be streamed live during descent, but made available several days later.

To get a very "rough" sense of what that footage may be like afterwards (with a lot more cameras), Doug Ellison has a good composition from the Curiosity landing here: https://www.youtube.com/watch?v=RZioPhfxnSY

The video wlesieutre linked of the Curiosity landing is a great reference of what you will experience for Perseverance's landing while watching it live. The video cuts short but about 10 to 30 minutes after landing they will likely have a half dozen low resolution images from the rover itself, much like they had with Curiosity.

I'm watching it again now. It starts off slow but really picks up once they get into the atmosphere. For those that haven't watched it definitely watch the 7 minutes of terror video first so you understand what is happening as they call it out.

I'm getting chills again lol

This is probably one of the best resources for watching live: https://mars.nasa.gov/mars2020/timeline/landing/watch-online...

https://mars.nasa.gov/mars2020/timeline/landing/

Every time I see a thread like this, I think of XKCD Spirit:

https://xkcd.com/695

Something profoundly bittersweet about that entry.

Movie recommendation: Moon (2009) sci-fi

The landing animation video (2/3 way down in article) is really amazing.

JPL produced a video titled "7 minutes of terror" that detailed the landing procedure they used for Curiosity, and it's worth a watch. It goes into detail on everything you see in the articles landing video: https://www.youtube.com/watch?v=Ki_Af_o9Q9s

its been updated for perseverance

https://www.youtube.com/watch?v=rzmd7RouGrM

https://www.youtube.com/watch?v=M4tdMR5HLtg

off-topic: more than 60% of page is just ads above fold.

That name is not easy to remember. A shorter more frequent word would be better.

Percy?

meet George Jettison.

A $2.7bn RC car.

> A $2.7bn RC car.

One that could find life and immediately invalidate every religion's current perception of the world. (Or at least require rethinking from religious leaders on how to adapt to this new information.) A lot of people - even atheists - will have to change their model of the universe. It would probably be the most critical and important moment in human history.

From there we have to start thinking about how to protect our own species. Because if we're not the only life, and it's as common as the next planet away, imagine what else lurks out there...

It would kick off the next, even bigger, space race.

Even if we don't find life, this thing comes so loaded with experiments and new engineering that it propels us forward for the next generation of planetary exploration tech.

If the past 3,000 years has taught us anything it is thwt religions won’t change any of their superstitions when presented with evidence.

> It would kick off the next, even bigger, space race.

So basically I should be excited about the potential a self-perpetuating beaurocracy

Your entire argument is that the goal of spending money on space exploration is to spend more money on space exploration? For people suffering on earth that’s a great argument for defunding taxpayer funded space exploration.

> For people suffering on earth

It's just a temporary state, I assure you. It'll all be over soon.

Hopefully. Human lifespans are way too long.

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