Are there any working theories why the 2 impactor probes (Deep Space 2) that piggybacked on the Mars Polar Lander did not work? Their failure should have nothing to do with the problem with the MPL lander since they were released far above the surface.

I beleive they were designed to withstand 100 gravities of deceleration and still function. Anyone?

Main theory I heard was that the terrain they ended up hitting was very soft and sometimes quite rolling - so they probably destroyed or burried too deep on impact

Doug

Yeah -- the theory I heard was that either they buried themselves too deeply to be able to send radio signals back out, or that they hit a hillside or inner crater rim at nearly right angles. While the impact at the semi-grazing angle that was anticipated would not have exceeded its designed G-load survivability, if it hit at more of a right angle, the sudden deceleration could exceed the design limits.

However, the most interesting reason for their failure I ever heard was in the TV series "The West Wing," which dealt with a fictionalized loss of both MPL (called "Galileo V" in the episode) and its two accompanying hard-landing probes. When told of the plan to crash-land two probes with the expectation of gaining telemetered data from them afterwards, the Josh Lyman character responded (quoting from memory), "Hasn't the Wile E. Coyote theory of physics been pretty well disproven?"

-the other Doug

That went right over my head.

What did that mean?

Do you guys think there is any merit in this type of impact probe? It does not seam there have been any successfull demostrations of it. I am pretty skeptical that a machine that can survive such a sudden deceleration can also do much science as well.

Thoughts?

If the ACME Spacecraft Co made spaceprobes at least we'd be certain that they'd go 'Beep-Beep!' after landing...

...whatever happened to the business of Bugs Bunny and Marvin on Mars, anyway?

I beleive they both blew up Planet X when they each tried to claim it. Right?

On a serious note, the Japanese LUNAR-B (I think) probe has *still* not made it into space - and it has several penetrators aboard...

Wile E. Coyote is the cartoon character who is always in pursuit of -- and never catches -- the Roadrunner in the many, many Roadrunner cartoons produced by Warner Bros. from the 1950s through the 1970s.

Wile E. uses every hare-brained scheme in the book to try and catch the Roadrunner (often with the help of outlandish products and weapons from the ACME Company), which always backfire on him. Most of the time, he ends up flying off the end of a cliff, hangs in mid-air long enough for a reaction shot, and then falls several thousand feet to make a "splat" on the desert floor below. He then always walks away and lives to pursue another day. It is this ability to survive what would appear to be non-survivable falls and impacts that would lead one to assume that the Deep Space Two mission was relying, to one degree or another, on the Wile E. Coyote theory of physics...

-the other Doug

Actually, while no one has ever actually said it on the record, I think the MER teams were going to "informally" name MER-A Marvin and MER-B Duck Dodgers (or perhaps just Daffy), but that NASA's PR flacks got the idea it would be *so* much better to have some fifth-grader name them.

In any event, there are indeed mission patches for each rover, with the MER-B patch featuring Daffy Duck as Duck Dodgers (in the twenty-fourth-and-a-halfth-century!) and the MER-A patch featuring Marvin the Martian. Here's a link with a decent view of both patches:

MER mission patches

I sort of wish they had used the cartoon names -- Spirit is an OK name, but Opportunity is just not a proper noun, and never will be. It's a terribly awkward name for a rover...

-the other Doug

I thought they wanted to called them Divorce and Exhaustion

Doug

I never read or saw that a report on the DS-2 penetrators was available. But they held a failure review investigation that was mostly ignored by the media. The conclusions was similar to Beagle: No "Smoking gun", unlike polar lander, but the vehicles had major deficiencies in design and testing and project management and were way not ready to fly.

Penetrators are useful and valuable, even if not "sexy". They're by far the best way to get seismometers where they're well coupled to the ground. The Viking 2 seismometer turned out to be an excellent wind guage, for example.

Note that the Mars 96 Soviet/international mission carried 2 hard landers and 2 penetrators on the main spacecraft. All <sigh> lost.

"I sort of wish they had used the cartoon names -- Spirit is an OK name, but Opportunity is just not a proper noun, and never will be. It's a terribly awkward name for a rover..." -the other Doug


It took me a long time to get used to the names Spirit and Opportunity. I guess I don't mind them now. But under the circumstances at the time I think we were lucky they weren't stuck with names like Freedom and Democracy.


I actually proposed names for the DS2 penetrators... it was a competition like the MER one. Of course mine were not selected.
Phil

I entered that DS2 comp as well - with Romulus and Remus. Scott and Ammundson were good names though - I liked those.

Doug

I wasn't aware of the competition at the time, but in the spirit of Phobos and Deimos, I would have entered the names Fear and Loathing.

Not that I would expect NASA PAO to *ever* select those names...

-the other Doug

Well, if they did that, then MPL would have to be called ' Las Vegas '

Doug

Can *you* think of a better way to get people to want to go to Mars than by putting Las Vegas up there?



-the other Doug

Amundsen and Peary, perhaps (both being noted polar success stories) - but DS1 would have been better called Scott and Oates (after all, we have heard nowt from them for 'quite some time').

Well, now that you happen to mention it (and thanks for bringing the subject up), I've got a little list of both some places *and* people who might be very popular choices for a one-way trip to Mars...

...of course, *we'd* have to go as well, just to ensure that they came to serious harm.

Perhaps there's a spare Golgofrinchan Space-Ark somewhere (AchOOOH!)...

I can't find the reports, but here is a reference to them:

http://www.space.com/scienceastronomy/sola...bes_000407.html



A major criticism was that there was no complete system test - they should have built a couple of extras and crashed one into Southern Utah or something.

As I recall, during post-failure testing, one of the batteries cracked at the highest impact level, but this was from a different battery lot, and there were no battery failures during prior testing.

Every single Mars landing has either come down harder, or used more fuel than expected during the descent and landing. I was unaware of the two hard landers on Mars 96, I will add them to my list, (thanks). This includes both Spirit and Opportunity. The unexpected force of these landings - Spirit very nearly exceeded the burst strength of the air bags - was attributed to a lateral vector. However, both of these landers contained rockets that were designed to null wind velocities.

There is a much more obvious answer, but the world is too myoptic to see it:

There is a non-Newtonian vector in the gravitational force that can be modeled as a texture in space: The closer a probe is to a massive object, like a sun, the slower an object with a given momentum will travel a defined distance. Using Newtonian mechanics, we underestimate the mass of planets and moons further from the sun than the Earth, and over-estimate the mass of planets closer to the sun. This is why impact missions to Mars fail, while a Pioneer probe, that was not designed to survive landing on Venus, did not. This is also why we are seeing rocks on Titan and Enceladus. Rocks, not water-ice rocks.

Surely this would also have killed Viking, Pathfinder, and the rovers. Anything big enough to have killed DS2 would have killed previous succesfull spacecraft as well.

The Mars 96 probes never left earth orbit incidentally.

Doug

I think this discussion belongs on a different board - such as Bad Astronomy's Against The Mainstream... Perhaps I am being myopic myself, but I wouldn't rewrite physics to explain a few spacecraft failures...

For God's sake, if there was any such force it would have shown up in ways that would have been detected by 17th-century astronomers -- if not before.

By the way, Cassini's and Huygens' near-IR spectrometers have firmly detected lots of water ice on Titan and Enceladus, along with some apparent organics (as expected) on Titan. They have NOT detected silicate rocks. I would hope we can avoid turning Doug Ellison's site into another romping ground for Hoaglandites.

I was THIS close ( finger and thumb just about touching ) from just deleting the post - but thought that would be a bit of overkill - I think the point is made, the guy was over the line in terms of what is and isnt right for here.

Doug

Well, we all know that the Deep Space 2 probes were eaten by the Great Mars Goblin! Same creature that took the Mars Observer, MPL, etc

My own personal question is: If the probes were designed to impact into sand, but instead hit ice, which is not very compressible, would that account for the "suboptimal outcome"?

you have been advised once - and that's the only warning people get. Off topic content culled. Once more, and it's this forums very first ban - please dont give me the option of doing that - Doug

I'm pulling from old memory, but as I recall the 200g limit included impact into hard rock - there was some shock absorption capability. However a glancing or lateral blow could have damaged areas not protected from shock impact.

What do you suppose is the likelihood of the opposite scenario? Instead of going crunch against a surface that was too hard, could the DS2s have been buried in a Martian snow drift? Would that have degraded the radio signals enough to make them undetectable?

The trouble is simply that -- as the failure report makes clear -- the things were so inadequately tested that there were three or four possible ways they might have failed WITHOUT even taking into account the possibility that they ran into some kind of freakishly hard, soft or sloping surface that would have wrecked them even if they hd been properly built.

Interesting thought. Studies indicate most of the Martian snow is "hard pack":

http://www.space.com/scienceastronomy/sola...w_011206-1.html


I don't know how 'hard' CO2 will pack in a low pressure environment: My personal experience suggests 'not very'. Based upon Opportunity's trouble with Martian sand, I don't think getting buried in a sand dune can be ruled out, either.

As Bruce said, there are many possibilities. Meanwhile, I get to identify threads of commonality.

Actually, it was overboard of me to bring up "Hoaglandites" -- but, really, there is no doubt whatsoever as to the strength of gravity in the outer Solar System, and there hasn't been for centuries. (That's how they found Neptune, remember?) Doubting that there is comes perilously close to Hoaglandism.

And anyway - the phrase is Hoaglanderati



Doug

The Messenger:
"Interesting thought. Studies indicate most of the Martian snow is "hard pack":
I don't know how 'hard' CO2 will pack in a low pressure environment: My personal experience suggests 'not very'. Based upon Opportunity's trouble with Martian sand, I don't think getting buried in a sand dune can be ruled out, either."

Because the martian atmosphere is mostly CO2, there are a lot of opportunities for vapor-transport in the snowpack and rapid grain growth. There've been studies in the last few years based on Global Surveyor thermal mapping of the polar cap ice including low-emissivity regions I think they've decided are glare-ice. You may get a lot of direct frost formation in the polar night directly into solid ice on the cold surface, radiating into space. Lidar data from the Laser altimiter do show polar night clouds, but they're not a massive constantly snowing CO2 cloud cap.

I'm sure there's been a lot of theoretical and data-analysis work on this the last few years that get absolutely zero press, unlike the "banyan trees" that Hoaxland and their dupes <including poor Arthur C. Clarke> have interpreted from the bizarre images of areas that are losing the winter CO2 cover

Doug:

My classical studies are not what they once were, but might it not properly be Hoaglandii Hoaxerus Maximus?

That is the dwarf variety, though, which favours being planted in a south-facing pit (nothing unseemly, no more than 60 ft deep).

Bob Shaw

The DS-2 concept of using a 45 deg. sphere-cone from atmospheric entry to impact was very clever. The 45 deg. sphere-cone with a hemispherical back shell is one of the few shapes that can be statically and dynamically stable all the way from orbit to impact. For example, the 70 deg. sphere-cone used with Viking, Mars Pathfinder and MER becomes dynamically unstable at around Mach = 1.8. If a parachute is deployed at that Mach number or higher then the 70 deg. design is better than a 45 deg. design because the greater bluntness means less thermal protection mass and the parachute can be deployed at a higher altitude (very important with a Mars lander). My main quarrel with the DS-2 concept was the use of a surface impacter. With a surface impacter, you're always at the mercy of "Murphy's Law", e.g. whacking into a big chunk of basalt. Historically, Mars always punishes the designer if a significant probability for failure is allowed. I like the idea of reusing the basic DS-2 aeroshell but rejecting the surface impacter. Instead I believe an "airbag decellerator" should be used instead. Normally with a Mars lander there is a mortar in the back shell that deploys a parachute. Replace the parachure with a kevlar fabric inflatable sphere. Have a helium bottle in the aeroshell and connect the bottle to the airbag with a braided stainless steel hose. Attach the hose to the airbag with a quick release that detaches when a certain pressure is reached in the airbag. Program the probe to mortar out the airbag at about Mach 3. The airbag would initially be flailing away behind the aeroshell, attached to it by the braided stainless steel hose. The airbag is slowly inflated until reaching its full shape and then detached from the aeroshell. The aeroshell would then proceed to destructive surface impact. Some quick-and-dirty numbers reveal that an airbag without payload would have a terminal velocity on Mars of about 35 MPH. Now suspend a very small payload at the airbag's center with kevlar strings and copper wires (to act as a dipole antenna). I estimate that one could get a 100 gm payload on the surface of Mars this way with the payload remaining within the inflated airbag after surface impact. Can any science be done with this sort of lander? At the very least it could be used for acquiring an atmosphere snapshot, i.e. acquiring a density versus altitude model of the atmosphere for that specific time and location on Mars. The aeroshell could carry an inertial measurement unit that measured the deceleration force. From the deceleration force it is possible to back out the local free stream density. The history of this deceleration force (atmospheric density versus altitude) could be stored in a flash memory that was part of the 100 gm payload within the airbag. After surviving impact, the 100 gm payload could uplink its data to a spacecraft orbiting Mars, e.g. MRO. The 100 gm payload would be simply a battery, a radio transmitter, the flash memory and timer. The payload would only transmit data when the timer indicated that an orbiter was overhead. You might be able to throw in a CCD camera as well for some surface images. I see this basic design as the ultimate low cost Mars lander.

Gary

There have indeed been quite a lot of abstracts on the physical consistency and growth patterns of the polar caps -- and, yes, the puzzlingly dark but cold "Cryptic" region of the south polar cap is now thought likely to be solid CO2 ice. The rest of the cap seems looser -- for meteorological reasons that are still unclear -- but it could still be fairly hard, and certainly the permafrost could be.

But keep in mind that back in the 1970s, Sandia Labs -- the main penetrator enginers -- were routinely crashing large penetrators into solid granite in the New Mexico desert with a wide variety of instruments -- including seismometers 100 times more sensitive than the ALSEP ones -- and having them survive just fine. There is no reason to think that the penetrator concept won't work equally well on other planets, provided NASA doesn't stupidly underfund their development and testing. The latter was almost certainly DS-2's Waterloo.

I never saw a "final investigation report" on the DS2 debacle, but the summary was basically that the probes should never have flown: "Not ready for Prime Time", in effect. Design was deficient, testing was deficient, I don't recall if they thought assembly was deficient.

(nods at Bruce) Yeah.. there was a lot of work on "Terradynamics" for penetrators. starting with vietnam era seismic traffic listening javelins for besides the HoChiMinh trail.

Don't forget Mars 96 carried (I think 2) substantial penetrators, with considerable instrumentation and afterbodies to be left on the surface with antenna and additional instrumentation. Damn shame that mission never launched properly.

I HAVE seen the final DS-2 report, and they thought EVERYTHING was deficient -- including a failure to determine whether the assembly was deficient or not by doing the most elementary testing. I'll see if I can hook the report's URL, but I know I have it on my CD-ROMs.

Yes, Mars 96 had two fair-sized penetrators in addition to its two small surface hard-landers. However, it was excruciatingly clear even before the launch (and commented on in many news articles) that the Russians were so short on funds, and had therefore skipped so many tests, that it would have been an absolute miracle if the spacecraft had worked even if it had been successfully launched. So help me God, they were assembling it in rooms lit by GAS LANTERNS.

Bruce Moomaw said



We have a ballistic range faciity at where I work. The acceleration experienced by a model launched from a light gas gun is comparable to what a surface penetrator might experience whacking through a chunk of granite at supersonic velocity. A few months ago, I went through the process of proposing the incorporation of a Motorolla 68HC11F microcontroller into a ballistic range model. With some rye amusement, I was politely told by our ballistic range expert that my proposal was technically unfeasible. The accelerations in a light gas gun are unbelievable (over 100,000 gravities). Reports that Sandia has pierced granite with surface penetrators carrying electronics should be treated with some skepticism. The accelerations experienced in a military (powder) gun are much less than a light gas gun. The electronics in a military penetrator might be as sophisticated as a microprocessor but are more likely to be some very simple electronic circuit optimized to withstand high accelerations (a warhead fuze). Also, more likely than not, the military penetrator is a meter long sharpened slug of depleted uranium with the electronics package mounted in the rear. The granite penetrating power of a depleted uranium slug compared to a DS/2 science package is an apples-and-oranges comparison. Did JPL ever launch a DS/2 science package into a basalt boulder? What were its survival statistics? If the experiment was never performed then the concept has no credibility.

I didn't say it was a DS-2 sized penetrator -- these were big penetrators, 1-2 meters long, with their entire front third or so being sharp-nosed solid steel. The NASA Technical Report on this subject was published all the way back in 1977, and they succesfully tested a wide variety of science instrument types on them. I'll see if I can dig it out.

Bruce:

The BIS Spaceflight Magazine also carried a couple of articles at about that time - and yes, they were *big*.

Bob Shaw

http://www.jpl.nasa.gov/marsreports/mpl_report_1.pdf




...It would be interesting to know what the calculated maximum g force was at 200 m/s, and whether these numbers include engineering margins.


p22



It is a shame to invest so much in getting a package to Mars, and not have either enough design testing or in-flight instrumentation to reduce the number of possible failure modes.

I see "Messenger" has beaten me to the punch in finding the Polar Lander/DS-2 failure report. (I hereby retract my crack about "Hoaglandites" -- but PLEASE don't question the basic validity of gravitational law in the rest of the Solar System. As Lt. Columbo said about cigars, this is something we DO know about.)

As for the lack of adequate funds for DS-2, this was just another result of the fact that Dan Goldin actually did believe in his squirrelly version of "better, faster, cheaper" -- as opposed to "smaller and more frequent", which is the part of it that actually works.

I found an interesting image of the two Mars 96 Small Station landers in the .pdf of the NASA 1996 Mars Missions Press Kit. Interestingly, the document mentions that they would use airbag technology (just two big ones) and says (p52) that the same methods were used for the early Soviet Lunar landings in the 1960s! And on p54 there's mention of the twin penetrator probes returning data for a full year after landing...

...these may be just sloppy reporting on the part of NASA, however - unless there were RTGs involved somewhere along the line.

Bob Shaw

Yep two small RTG's per landers - 86kg total mass, 12kg landed. Much more detail on this Mars 96 page
The small landers had 7kg of instruments:
Temperature, Pressure, Humidity, Optical Depth, Ion Anemometer, Alpha, Photon and X-Ray spectrometers, Magnetometer, vertical seismometer,, Panoramic Camera, Oxidation, experiment Descent Stage temperatur, pressure and accelerometers, Descent imager.

The two 45kg penetrators - powered by a single 0.4W RTG each had 4.5kg of instruments.
Camera, Temperature, pressure, Wind speed, humidity, Gamma Spectrometer, X-Ray spectrometer, Alpha Spectrometer, Neutron Spectrometer, Grunt Accelerometer, sub-surface thermoprobe, Seismometer, Magnetometer.

1 year planned surface lifetime for all four "landers".

Pretty compact - shame they ended up in the Indian Ocean.

There were. In fact, there was concern because the nuclear material got dumped on South America.

Mars 96 - total amount of Pu - 200grammes.

If you want to be afraid of Plutonium - come live around here. I have Sellafield sitting happily just across the Irish Sea from me +- 100 miles away more or less. BNFL acknowledged that there's about 28kg of Plutonium "unaccounted" for as of February of this year. Fair enough, tricky business and all that, bound to lose some. Then in April one of their systems leaked 83,000 litres of waste being reprocessed (that's what they do in Sellafield) - mostly nitric acid but with about 160kg of Plutonium and 19 tonnes of uranium dissolved in it. That wasn't lost thankfully but it's proving a bit messy to clean up.

On the plus side they plan to reduce their emissions (ie the stuff they pump into the Irish Sea) of Technetium-99 by 90%. That's from the current 90TBq. Three Mile Island released a total of 0.55 TBq (although that was Iodine-131 which is much nastier).

Given that I have to live with the stuff gently glowing in the sea beside me, can't we at least put some of it to good use and throw it at Europa\Titan\Mars? Pretty please.

Well, Mars 96 wouldn't have worked even if it had been successfully launched -- news reports of the time routinely remarked on how the Russians, by then, had nowhere enough money even to test its components at all, let alone adequately. (They were -- so help me God -- assembling it by the light of GAS LANTERNS because they couldn't afford electric lights for the assembly building.)

Quite a lot of other detail at http://www.iki.rssi.ru/eng/index.htm - follow the links for interesting Venera etc images.

Bob Shaw