Wreckage Of Beagle 2 Found? Options

[djellison]

Helen just found this....

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?Vie...item=6590449480





Doug

[JRehling]

I believe that Viking had pretty good margins against density variations.  The best way to get margin is to have more propellant available.  Much of the "difficulty" of landing on Mars comes from using a landing system like MPF/MER, which has very, very thin margins because the RAD firings happen so late in the descent and don't provide all that much delta-v.

It's interesting that the entire MER package is much heavier than the Viking lander package, but the Vikings had 85 kg of propellant (starting in elliptical Martian orbit?) vs. the MERs 50 kg (starting in interplanetary cruise). The comparisons end up a bit apples and oranges, but one immediately wonders if losing some descent hardware and gaining some propellant isn't a good tradeoff.

[djellison]

Dont forget the equiv. prop mass of the RAD and TIRS rockets in the MER backshell. I dont know if the figure are out there, but they bring just about 900 very-ish-KG from about 180mph to 0mph in about 3 seconds - it's quite a whack and so there must be quite a lot of mass within that lot.

What still suprises me is the ammount of metal about on these vehicles when carbon composites would surely offer advantages in strength and mass. OK - so it lunched itself in the process of landing, but the basic B2 structure was actually built by the composites wing of the McLaren F1 team.

Doug

[The Messenger]

I am only now coming to realize how hard it actually is to land on Mars because of its peculiar halfway nature.  As Ed Strick (and Rob Manning) say, it's very hard to utilize either purely aerodynamic braking or purely rocket braking to land on it, and Mars' thin air density has a height profile such that it's difficult even to combine the two effectively enough to get the braking job done in time.  We may actually have been very lucky up to now to pull off as many successful Mars landings as we have -- most of the previous failures (Mars 2, 3 and 7; Polar Lander) were due to unconnected technical problems, but Mars' atmosphere alone may seriously endanger landers, and may conceivably have done in both Mars 6 and Beagle as well as almost killing MER-A.  And the bigger the lander, the more serious the problem rapidly becomes.

Both of the Viking craft used more of their fuel than expected (8-15%), but still held excess in reserve. Every single Martian landing craft has enter at a higher attitude and come down harder than expected, deployed parachutes later than expected, and left unanswered questions about their parachute drag coefficients and descent profiles. Every one. With lower engineering margins, the Mars 2,3,6, Polar lander and Beagle did not have chance.

The MRO has the potential of providing a definitive answer to these curiousites, but you must be willing to look at the possibility that there are very weak, second order gravitational effects. Weak second order effects, based upon the total mass of a system cannot be ruled out from our earth-moon platform, because the local mass-fraction is dominated by the solar mass. But further from the Sun and orbiting at an altitude of only 150 km, the MRO will sense gravity anomalies that are a full and unexplicable order of magnitude greater than the 300km orbiters.

[ljk4-1]

The news that Beagle 2 may have been spotted on the surface of Mars in the immediate vicinity of where it was expected to land was welcomed by the European Space Agency.

Full story:

http://www.esa.int/SPECIALS/Mars_Express/SEMAPB8A9HE_0.html

[nprev]

Helen just found this....

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?Vie...item=6590449480

Doug

Har har...think I'll try to undercut him by offering all of the Russian landers in a package deal (as-is with no warranties, of course)!

[Guest_BruceMoomaw_*]

Oh, gadfry, Messenger, are you still peddling that stuff about major violations of the laws of gravity elsewhere in the Solar System? Especially when the only thing we need to explain these crashes is the major fluctuation in Mars' air density already known to exist?

And Mars 3, don't forget, actually made it to the surface -- it just broke down, for unknown reasons, 90 seconds later. V.S. Perminov, who was associated with the Soviet Mars program, writes that he suspects a static discharge caused by the major planetwide dust storm in which Mars 3 landed as a possible cause (and, in fact, static discharge was also listed as one of the multitude of possible causes for the Deep Space 2 failures).

He also provides -- for the first time, I think -- an explanation for the Mars 2 crash: because of the Soviets' lack of faith in the quality of their own deep-space radio tracking, the craft was equipped with its own Autonav system that sighted on Mars several days before encounter and made a final automatic course correction to put the lander into the right entry corridor. But because the Soviets had slightly incorrrect data on Mars' true ephemeris (which, ironically, was corrected only a year later during the US/Soviet exchange of planetary probe information), the lander entered at too steep an angle and therefore crashed (shades of Mars Climate Orbiter!) He doesn't speculate on the cause of the Mars 6 failure -- although, given all those crumbling transistors on the 1973 Mars probes, it may simply have failed to fire its last-second retrorocket.

[Guest_BruceMoomaw_*]

I should add that the Polar Lander failure report does not list lower-then-expected air density as a possible cause for that failure -- and the software flaw discovered by the Board is fully adequate by itself to explain that crash (although it's always possible that something else wrecked the mission even before then, since a number of possible alternative causes ARE listed).

[edstrick]

Note that the Viking landers directly measured the gravity of Mars while sitting on the surface with their entry/descent accelerometers and got a decently accurate estimate for each lander of it's radius from the center of the planet. That would not have been possible if there were non-square root, or non-trivial "second order" whatever that means in this context, deviations in Mars' gravity from that determined by inter-planet peturbations, flyby estimates, and orbital measurements.

[djellison]

Messenger's gravity 'thing' has appeared here before, and he was suspended from the forum for a month for continually spouting pseudo science.

Infront of everyone here - go down that path again, and I'll just ban you. I'm not having that pseudo-science junk in this place. Speculation, yes. Discussion, yes. Debate, yes. Crap? No.

Doug

[Guest_PhilCo126_*]

Well, I cannot make up anything from the images and I guess we shall have to wait untill Mars Reconnaissance Orbiter is operational in April - May 2006...

Meanwhile:


Merry Christmas & Enjoy the end-of-year period !!!

... all the best for the New Year 2006 !!!

[ljk4-1]

And Mars 3, don't forget, actually made it to the surface -- it just broke down, for unknown reasons, 90 seconds later.  V.S. Perminov, who was associated with the Soviet Mars program, writes that he suspects a static discharge caused by the major planetwide dust storm in which Mars 3 landed as a possible cause (and, in fact, static discharge was also listed as one of the multitude of possible causes for the Deep Space 2 failures). 

I remember reading that Mars 3 may have kept working just fine on the surface - it was the orbiter that somehow lost the link with the lander. Any details on this?

I wonder if it stored any data onboard? Would it still be readable if so? Yes, I realize I am talking about a 1971 Soviet computer.

[RNeuhaus]

I remember reading that Mars 3 may have kept working just fine on the surface - it was the orbiter that somehow lost the link with the lander.  Any details on this?

I wonder if it stored any data onboard?  Would it still be readable if so?  Yes, I realize I am talking about a 1971 Soviet computer.

Enclosed is the data from astronautix web page about Mars 3 correspondient to Soviet unmmaned space M-71 :May 1971 Mars 3 Program: Mars. Launch Site: Baikonur . Launch Vehicle: Proton 8K82K / 11S824. Mass: 4,643 kg. Perigee: 1,528 km. Apogee: 214,500 km. Inclination: 60.0 deg.:
The descent module (COSPAR 1971-049F) was released at 09:14 GMT on 2 December 1971 about 4.5 hours before reaching Mars. Through aerodynamic braking, parachutes, and retro-rockets, the lander achieved a soft landing at 45 S, 158 W and began operations. However, after 20 sec the instruments stopped working for unknown reasons. Meanwhile, the orbiter engine performed a burn to put the spacecraft into a long 11-day period orbit about Mars with an inclination thought to be similar to that of Mars 2 (48.9 degrees). Data was sent back for many months.

Cherry Christmas

Rodolfo

[mcaplinger]

...orbiting at an altitude of only 150 km, the MRO will sense gravity anomalies that are a full and unexplicable order of magnitude greater than the 300km orbiters.

A couple of points:

MRO's mapping orbit isn't at 150 km -- it's between about 250 km and 320 km. Early in mission planning a lower periapse was considered, but this wasn't chosen.

Both MGS and I believe Odyssey routinely went below 150 km during aerobraking.

[The Messenger]

A couple of points:

MRO's mapping orbit isn't at 150 km -- it's between about 250 km and 320 km.  Early in mission planning a lower periapse was considered, but this wasn't chosen.

Bummer. The mapping will provide much more detail, and hopefully provide better insight into what is proving to be the ellusive - the moment of inertia.

Both MGS and I believe Odyssey routinely went below 150 km during aerobraking.

I think it is how the degeneracies in the harmonics have been identified, but I do not fully understand the details.

I remember reading that Mars 3 may have kept working just fine on the surface - it was the orbiter that somehow lost the link with the lander.  Any details on this?

I wonder if it stored any data onboard?  Would it still be readable if so?  Yes, I realize I am talking about a 1971 Soviet computer.

It would be fun to send one of the MER's on a long-hull mission to check it out...extend the mission to 2304...

Mars 3 impacted at about twice the expected velocity (~20m/s), but was designed to withstand such an impact. Since little in the way of lightning has been noted by MER's in a year of exploration, the possibility that the quick zap out was due to static effects is appearing less likely.

http://klabs.org/richcontent/Reports/mars/...oad_to_mars.pdf
(Soviet Report on the Difficult road to Mars, this is a good read.)

http://nssdc.gsfc.nasa.gov/database/Master...og?sc=1971-049F

The surface gravity numbers I have for the Viking probes are 1.5% above NASA's currently published estimate (3.725 Viking mean, current NASA: 3.71m/s^2), but I do not know how this current value was derived. Until the moment of inertia is pinned down, the unknown mass distribution limits the resolution of the surface gravity.

http://techreports.larc.nasa.gov/ltrs/PDF/...76-cr159388.pdf
(Vintage Viking document, also a fun read)

As per Doug's request, I will keep my speculations-as-to-cause off the board, but everyone appreciates the importance of noting and trying to understand the cause of anomalies.

This board is too good to miss - for any reason.