Bennu’s forbidding gravelly surface


Genesis cover

On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.

 
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"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs." --San Antonio Express-News

Gravelly Osprey landing site on Bennu
Click for a higher resolution version.

On May 26 the OSIRIS-REx science team completed their first rehearsal and close approach to their back-up sample-grab-and-go site on Bennu, dubbed Osprey, getting as close as 820 feet. The image to the right, cropped and reduced to post here, shows that sample site within the white box. According to the image caption, the “long, light-colored boulder to the left of the dark patch, named Strix Saxum, is 17 ft (5.2 m) in length.” Note also that they have rotated the image so that east is at the top in order to make it more easily viewed.

This particular spot in this crater is actually a revision from their first choice from early in 2019, which originally was to the right and below the dark patch in the center of the crater. After six months of study, they decided instead on the present target area above the dark patch, because it seemed safer with the most sampleable material.

So how safe is this new location? Let’s take a closer look.

Osprey landing site up close
Click for full resolution.

The photo to the right is taken from the full resolution mosaic of today’s image [a very large file], and focuses specifically on the region in that white box. Even so, the image resolution is reduced. To see just this section at full resolution you need to click on the picture.

This is a very gravelly surface, with no dust, and many many pebbles larger than an inch across. Since OSIRIS-REx’s grab-and-go equipment is designed to collect objects smaller than 0.8 inches, there is a lot of stuff here that it can’t grab, but if disturbed could very well damage the spacecraft. And since Bennu’s gravity field is so weak, any contact with it will certainly disturb it, causing many of these pebbles to fly all over the place, as we saw when Japan’s Hayabusa-2 spacecraft did two touch-and-go sample grabs on the similar asteroid Ryugu. (Images from the first can be seen here, and a movie of the second here.)

In other words, the sample grab at Osprey would be a risky proposition.

If you are now saying thank goodness this is the back-up site, don’t. The primary site Nightingale is really not much better, and is probably as risky. The actual sample-grab-and-go at that primary site is presently scheduled for October 20, with a final rehearsal getting to about 131 feet set for August 11.

Keep your fingers crossed that all goes well. It will likely take a bit of praying to help the engineering.

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9 comments

  • LocalFluff

    Thanks to SpaceX, it is now inexcusable to design space missions with such small margins for failures and surprises. Both Osiris-Rex and Insight are having sever problems because designers did not allow for any surprises. Coming missions can add another ton or to to the probes so that if they plan to dig up a sample, they use a proper shovel that can scoop out rocks as well as dust. If they plan to drill down in the ground, they use a real drill. The time of minimalist spacecrafts that spends many millions and many years on lowering the mass by half a pound, and fail because of it, is over.

  • Edward

    LocalFluff,
    Keep in mind that the low gravity of many of these objects makes drilling, shoveling, and scooping difficult. Rosetta’s Philae probe attempted to anchor to 67P but failed. It is tricky, indeed.

    The Insight team expected Mars’s soil to be more compact or clay-like. Maybe they were unlucky with their location, or maybe Mars’s soil is so very different than Earth’s.

    The OSIRIS-REx team expected more dust or smaller rocks at some place, but they didn’t find such a spot. Oh, such disappointed expectations.

    We are learning lessons about such close exploration, and as you note, SpaceX’s drive to make launch less expensive should help us to do more exploration and learning. One of these decades, we should get good at it.

    A century ago, or so, life was exciting because of the rapid and surprising changes in technology. This century, life is exciting because of the rapid and surprising changes in knowledge of the universe around us.

  • LocalFluff

    @Edward,
    Yes, that’s kind of my point. Space probes are traditionally designed so very skinny that they just barely could pull off plan A under the most optimal conditions. And no plan B is available, but bet everything on a guess about conditions of the target, about which they don’t know nearly as much as they assume from first theoretical principles. Nothing has ever been removed from any asteroid. Nothing has ever been put down in Mars’ soil (other than the <65 mm MSL drill).

    So now these two failing missions, Osiris-Rex and Insight (both failing pieces of equipment of Insight and of the Rosetta Philae landing systems, were btw made by German DLR, with very tiny budgets inflated by guesswork and hopes). So now two $800+ million projects that have taken a decade to produce, are close to failure. If they had spent 10% of that on Falcon Heavy, they could've used large robust and duplicate tools to manage any imaginable uncertainty about the conditions at the target. And save years of time. And actually, they spent at least twice that on the small launchers they did use! That multiplied development costs and the risk taking. What is expensive is the payload, not the launch. Larger launchers save hundreds of millions per mission because it allows much higher success rate and much cheaper and quicker design. Now it is as if they are spending $10,000 extra on a car purchase in order to save $100 a year on gasoline.

    ESA's/Russia's ExoMars rover will not launch as planned this conjunction summer, but in 2022 (because of parachute problems, because they chose to not use parachutes that have worked on Mars several times before). It is supposed to drill 3 meters deep (100 feet). I predict that the drilling will fail miserably if an attempt ever happens.

    And JWST developed, I don't know when, but before the smart phone was invented, has costs billions and failed for many years, because of the focus on making it as vulnerable and fail prone as possible in order to save a few grams here and there and thus a fraction of the 2% of total budget that the launch cost makes up (Ariane 5 launch costs about $200 millions, JWST costs $10,000, so why not use two or three Ariane 5 to dock its components in Earth' orbit? Since it was developed a decade or two earlier than Falcon Heavy?)

  • Edward

    LocalFluff,
    You wrote: “So now two $800+ million projects that have taken a decade to produce, are close to failure.

    Well, I guess I’m glad you weren’t on any of the design teams I was on. Otherwise we would have been so worried about plan B and Plan C that there would not have been weight budget left over for the other experiments. With an attitude that trouble with an instrument or an unexpected hazard with the surface conditions means complete mission failure, we would be too afraid of failure to try anything, and right now we wouldn’t have the Insight seismometer on Mars or all the data that Osiris-Rex has given us.

    I especially love the part where the proposal team should have planned to use an unannounced rocket that would not be available until a year and a half after the launch date. Maybe all future probes should wait for Starship to come online so that they can all be 100 tonne monstrosities that do all the science possible, with backup systems and emergency backup systems. Or maybe the 130 tonne super SLS.

    On the other hand, if anything went wrong, you would still be upset and critical.

    Many instruments and satellites have their troubles. Robert reports on several of these. Satellites going into safe mode or instruments needing more TLC than expected. Despite this, missions continue and data is collected.

    To paraphrase Donald Rumsfeld, you go to science with the technology you have, not the technology you might want or wish to have at a later time. In the case of science, the way to develop the technology you wish to have requires that you test it in the field a first time.

    because they chose to not use parachutes that have worked on Mars several times before

    Different parachutes work for different weight loads. There can also be different atmospheric or trajectory conditions under which they open. Don’t assume that every Mars probe has used the same parachute. Wouldn’t it be a shame to lose a whole mission from a failed parachute because we were trying to save a dime.

    Wait. Wasn’t saving money one of your complaints? You recommended spending money on extra Ariane 5 rockets?

    why not use two or three Ariane 5 to dock its components in Earth’ orbit?

    Because one Ariane 5 launch will do. Breaking up a spacecraft into multiple parts for assembly in orbit does not make the spacecraft less complicated, and the need for the docking or orbital assembly adds complexity.

    You may not like the trouble that comes from trying out new technologies in space, and in the case of JWST this and other problems caused unnecessary delays, expense, and loss of other astronomy missions. Perhaps JWST should have been cancelled a decade ago (and WFIRST cancelled last year), but someone has to try new things, otherwise we would still be launching Explorer 1 satellites — and we may even be afraid to launch that one for fear of failure. Maybe we should have given up rocketry the first time one blew up, but wouldn’t that have been a shame?

    Someone needs to be brave enough to risk failure. Fortunately, the U.S. is the home of the brave. As you pointed out, Germany’s national space research center is also brave enough to try new things, risking failure and criticism.

  • LocalFluff

    It seems to me that space exploration is plagued by nerds who like to do things in as a difficult way as possible, just because it’s fun and someone else is paying, not caring about producing results. We’ll see SpaceX humiliating them once they start landing on Mars, just like they have humiliated the military industrial complex when it comes to rocket manufacturing (and isn’t the US entire security situation totally dependent on working ICBM’s? It is very worrying how extremely mismanaged this has been all these decades!) If you don’t know whether your travel destination is like Sahara or Antarctica, because it’s the first time anyone goes to such a place, one won’t survive by just making a blind guess.

    This “mole” on Mars is a design failure. They could’ve asked a construction equipment manufacturer like Hilti to design something that can get a few meters into soil of unknown properties. It’s being done daily on Earth. There’s nothing difficult about such a routine, unless one makes up the requirement that it must weigh less than half a pound.

    And an asteroid sampling spacecraft that cannot pick up a rock, is a design failure. They didn’t expect to find a rock there??? Wouldn’t rocks be much more interesting scientifically, than any dust on the surface that could’ve gotten there yesterday from who knows where? They just took a high risk bet.

    The Rosetta Philae lander had three separate systems for landing instead of bouncing, as it did anyway. A cold gas thruster (that failed already during transit), grappling claws on the landing legs, and a harpoon. So they had plans A, B and C. Still Philae was tiny. It is not impossible to have backup systems that solves a problem in very different ways. (Perhaps Insight should’ve used the harpoon concept, getting down there in one explosive shot instead of spending years and years accomplishing nothing.)

    Lowering launch costs from 8% to 2% of total mission budget might sound good. But not when it is done by quadrupling the total budget, and quadrupling the risk for mission failure! Out of hundreds of dockings (Apollo, ISS, Soviet space stations) I have only heard of two failures. Agena-Gemini in the 1960s and a Progress-MIR in the 1990s. I don’t understand why some people still today claim that it be so difficult.

  • Edward

    LocalFluff,
    You wrote: “SpaceX humiliating them once they start landing on Mars

    What an excellent example. SpaceX is full of those same plaguing nerds, and it also has its own developmental and operational setbacks. The difference is that SpaceX is braver than most of the aerospace industry, but like the U.S. aerospace industry it is willing to risk failure and criticism.

    one won’t survive by just making a blind guess.

    My guess is that this is why we send unmanned probes before sending people. The probe gets to take the risks of the “blind” guesses.

    This “mole” on Mars is a design failure.

    The mole works as designed. The problem was the “blind” guess. I’m not sure when was the last time you saw construction equipment, but it is generally too heavy to lift to Mars. Generally, drillers who do not drive piles will add pipe as they reach the end of the length of the last pipe. This process is fascinating to watch. The lander had a maximum length that was shorter than the depth to which they hope to drive their probe, so they would have had to add some form of complicated connection mechanism to get there without the hammer method.

    Weight limits are not “made up.” They come from the available vehicle performances and from the desire to have multiple instruments on each $800 million probe.

    They didn’t expect to find a rock there???

    This explains much. You didn’t read the links or even Robert’s post.

  • LocalFluff

    “SpaceX is full of those same plaguing nerds”
    Except for the detail that SpaceX delivers. These skinny probes fail. The fault is not with the nerds, but how they are organized. That must be evident to all by now! Their organizational error was to focus on minimizing probe mass, instead of maximizing launcher mass capability. Because they didn’t have any incentive to care about economy of it all.
    That’s why I KNOW that SpaceX will humiliate all government robotic spacecrafts too. That’s the difference between parasites and creators. Creators optimize rationally, parasite ruthlessly just take from others and don’t care about costs or failures. They had a fun ride anyway.

    “The mole works as designed.”
    Id est, it DOESN’T WORK!!!
    But some group of nerds and their exotic suppliers of otherwise also useless stuff, got well paid for many years.

    Did they even ask for example a Hilti salesman:
    “- Could you put something that drills down a thermometer from such a thing as the Mars Polar Lander platform, for $100 million dollar?
    – A hundr..??? Let me check wit… Just skip that: Jawohl Yes we can!”

  • Edward

    LocalFluff,
    You wrote: “The fault is not with the nerds, but how they are organized.

    Really? Yesterday you blamed the nerds themselves, “who like to do things in as a difficult way as possible, just because it’s fun and someone else is paying, not caring about producing results,” but you did not blame their managers or the system they work within. Why is it that your arguments shift every time you turn out to be wrong in the first place?

    Their organizational error was to focus on minimizing probe mass, instead of maximizing launcher mass capability.

    Will there ever be enough launcher mass capability for you? It is easy for you to be critical after something goes wrong, but the real challenge is to be the nerd who makes the things that work with what we have today, and most instruments, experiments, and spacecraft do work. Strangely, your complaint revolves around them coming across unexpected terrain. Even your example of having backup and emergency backup plans turned out to be a failure, so your solution may not be correct, after all. Those backups were weight that was wasted and could have been used on one or more other instruments on Rosetta.

    Creators optimize rationally, parasite ruthlessly just take from others and don’t care about costs or failures. They had a fun ride anyway.“.

    You are so right about that. Three years after the loss of Mars Observer, I worked with the engineers and technicians who built it, and they didn’t care one whit whether the thing made it to Mars or not. They never told me that they were disappointed about its loss. No disappointment at all that their creation didn’t do any science. None at all.

    By the way, that was a sarcastic remark, in case you really believe the malarky that you wrote. (I believe that you are actually smarter than you are coming off, but that you are trolling.)

    it DOESN’T WORK!!!

    As designed, it does. It was designed for different soil conditions than it encountered.

    You have no idea what you are talking about, and you still haven’t read Robert’s post or his links.

    But some group of nerds and their exotic suppliers of otherwise also useless stuff, got well paid for many years.

    There you go again! Blaming the nerds. You blame people with more disappointed expectations than you have, yet you claim that they failed without any care or consequence. What about the Mars scientists who gave the soil conditions for the nerds to design to? Aren’t they more culpable for the blame you assign than are those who followed the direction given to them? Whose is to blame that Insight found different soil conditions than anticipated? How bout those who mis-predicted the terrain conditions for Osiris-Rex and Philae?

    On the other hand, the Insight scientists (and Osiris-Rex and Philae scientists) are the ones who put more than a decade of work into their probe(s) but may not be able to publish the papers that they had hoped. Talk about disappointed expectations!

    *Sigh* It is too bad that you are so set in your thinking. My responses to you are obviously futile, except as an exercise in discussion and reasoning. After I pointed out that scientists are stuck with the technology of the day, you insist that they should wait for more advanced technology. You do not learn the point I make when I say things such as: “you go to science with the technology you have, not the technology you might want or wish to have at a later time.” If you don’t do the science that is possible to do now, then when will you ever do it? There is always going to be better technology just around the corner, but you need to do what you can when you can do it, otherwise you will never do anything.

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