The margin for the mass of Mars is not 14 percent. This is not an engineering margin. You can calculate with very good acurracy the mass of Mars if you just use some data about the orbits of phobos and deimos from anywhere in the web.

Now, if there was a mistake 14 percent for the mass of mars, as you stated earlier, well this would not just account to some extra heating on the heat shield. It would also mean for example:

1. Lander missing competely the landing ellipse
2. Lander entering with the tottaly wrong entry angle and velocity, so probably completely destroy

etc etc...

Your solutions should be "global" and not try to give answer to a small detail.

Plus, as for the ablative heat-shield burning through, maybe its just a matter of impact what you see, but also isn't the principle for ablative heat shileds that part of their material should burn and vaporize?

It seems to me the apparent situation with the heat shield is optimal. Since the lander did obviously survive as intended the shield worked as intended without a single gram of wasted weight. Perfect anticipation of the requirements.

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When I am done here I think I will go create something from metal.

Your making stuff up again. Did you ever think that no mention was made of "residual heat" because there wasn't any to mention? BTW, how much is too much coincidence? Is it coincidence when reasonable explanations can be made without resorting to changing fundamental physical constants?

Just because you can't understand why Spirits electronics may have been warmer doesn't make it so. Exactly how is the heat shield supposed to look?

Your assuming there is "residual heat" to dissipate. We have no evidence of this. According to this, the outer surface of the heat shield heats to about 1447 deg C while the inner surface stays at about room temperature. What evidence do we have that this was not the case for Spirit?

The Mars Polar Lander failed due to a software error causing it to prematurely terminate it's landing rocket. This wasn't just "entertained" by NASA, it was a conclusion that was based on re-creating the problem in the lab. Where do you get your information?

There's no evidence that Mars mass is 14% greater than we've measured. Don't you think someone might have noticed by now?

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"A mystic is a person who is puzzled before the obvious but who understands the nonexistent." -- Elbert Hubbard

All this nonsense about residual heat is just plain ludicrous. Where I live it is currently about -20c this morning. I parked my car last night with the engine at full operating temperature, about 110c. It takes about four hours maximum for the entire vehicle including the mass of the engine block to cool to ambient. Even in a near vacuum normal radiative cooling would result in the same thing.

It's like Jerry has been reading too much of the Weekly World News.

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When I am done here I think I will go create something from metal.

I don't think that's what they had in mind for the Moon-to-Mars vision.

Sorry for the OT post, that URL was just too funny.

Sorry: Mars Orbiter and Global Surveyor…I think.

I have mixed up the names of Mars missions so badly I question my own credibility, (just so you don’t have to).

The mission failed during or shortly after entry. No one knows for sure why. End of story.

This is consistent with your Russian Mission Optics report, which is utterly cool, thank you, as the system waited 90 seconds before transmitting, although I’m not sure I would consider a 75km/hr landing “soft”.

As I stated before, it is difficult to separate the impact damage from thermal damage. If you look carefully at this image, there is a complete displacement of the honeycomb structure right about where the back panel made contact with a submerged boulder on the Martian surface. This coupled with the separation along the structural ridge line (in the same photo), if you add these to the trail of blacken debris between the impact crater and the final resting place of the shield, it is reasonable to conclude much of the damage to the heat shield is due to impact.

However, if you look at the ablative material still partially adhering to the backplate, it is clear the thermal effects have completely degraded the protective capacity of the filled honeycomb matrix all the way to the backplate. If Opportunity had entered an oxygen rich atmosphere, this could possibly be written off as post-entry burning.
I think this heat shield survived entry by the slimmest of margins. I think the damaged part of the backplane (highest edge in this closeup photo) actually shows burn-through near the edge. If this is correct, there would have been significant heating, possibly even some heat damage to Opportunity, and this could even show up in a close examination of the landing platform.

Engineers will not be pleased to see the narrow margin-of-victory this heat shield indicates: Space vehicles are usually built to a design criteria of ~1.4 for metal parts and 1.5 – 2.0 for composite structures. After the Polar lander and Climate Orbiter debacles, they clearly would have been conservative in the design of the entry vehicles of Spirit and Opportunity. Rather than being pleased, I will bet this months paycheck that at least one NASA subcontractor is aghast at the sight of this heat shield.

Your car was designed to dissipate heat, not retain it. With insulation and reflective surfaces it would take much longer to cool. and it could take days for it to cool if you wrapped it in aluminum foil, surrounded it with air bags, and parked it on Mars shortly after atmospheric entry.

I will admit I am fishing here, looking for more information about how Spirit was packaged, if the measured overheating is consistent with a near-heat shield failure, and why they forced Opportunity’s parachute to deploy early, and did the Russians expect to impact at 75km/hr, and if not, what they think caused the rapid descent, and why they think the parachutes on Viking I & II deployed late, and why Voyager II did an unprogrammed burn after passing through Saturn’s rings – I can’t find this information.

Cosmologists are using free parameters with abandon, trying to shoe-horn what we observe into the physical world we think we know. I don't like that - so in a way, I am more conservative than the established scientific community - I don't think we should introduce fudge factors like Inflation, Dark Matter, and Dark Energy without first taking a good hard look at the basics.

I guess I ask for that. Like I said, if I am not right, at least this thread has been entertaining...and I'm glad I don't live where Evan does.

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jwj

It's ok not to know.

Actually my car is not designed to dissipate heat unless needed. It has insulation aplenty and a lot more thermal mass. More to the point all that reflective foil and other insulation is just as effective at keeping heat of reentry out as in. Not the right answer. Logical answer? Mars has a climate. Some days are warmer than others.

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When I am done here I think I will go create something from metal.

Jerry, your willingness to "wager" is irrelevent. Your continued "mind reading" is irrelevent. If you can show that a subcontractor was "aghast" at the sight of the heat shield, then by all means share that information with us. If not, then (as Hamlet pointed out) stop making "stuff" up. It really makes you look silly.

Jerry was complaining about the dearth of MER technical information. Here are a few NASA technical reports that have some bearing.

Atmospheric Analysis provides some insight into modeling of the Martian atmosphere and how those models were used as input to EDL.

EDL Pre-Launch provides information about the Entry, Descent and Landing Phases as they were designed.

EDL Post-Arrival provides similar information to the above with the inclusion of predicted and reconstructed values for various EDL parameters.

Looks to me like they did a pretty good job.

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"A mystic is a person who is puzzled before the obvious but who understands the nonexistent." -- Elbert Hubbard

Is this still the variable G thing? I'm not sure why you are proceeding to defend this concept when you (seemingly) can't explain the objections brought up in the Do we know why there's gravity? thread.

I did, but you did not understand my answer. Here is an abbreviation of the dialogue.
An elliptical orbit is very similar to a pendulum and independent of mass, to the first order. This would be true even if G were not a constant, as long as the rate of change in G is constant for both masses. Since for a comet, the mass of the sun >> mass of the comet, (and I am talking about varying the G constant relative to the Sun.), We could not detect this variation to the first power, in a comet, regardless of the mass of the comet.

HOWEVER

Any second or higher order perpetuations of Haley’s comet are a function of mass, therefore, you must accurately know the mass of the comet in order to carefully calculate these second order effects upon the orbit. Since we do not know the mass of Haley’s comet, we have determined the mass of Haley’s comet by observing second and higher order effects.

If current theory is correct about both the mass of and the orbit of Haley’s and other comets, gravity cannot have the inertial component I have described. But if there is an inertial component to gravity we may be underestimating the density of comets. That is why the results of the Wild 2 mission are so important:

Gases erupted from this comet like it was exploding out of fissures is not the 'melting snowball' we were all taught about. Contrary to what we are all reading about the accuracy in the measurements in the orbits of comets provide proof of Newtonian Keplar theory, the close-up physical evidence is indicating just the opposite: If the meteorites we find on the earth are made of the same material as comets, comets are much too heavy to satisfy the second order gravity equations with Newtonian physics.

We have already learned during the Cassini mission a fact contrary to theory about the makeup of the outer solar system: Iron has been detected across much of the surface of Phoebes. If the other moons are showing similar iron content on exposed surfaces, it becomes very difficult to explain why the moons of Saturn are so much less dense than the inner solar system.

edit - punctuation, clarity, qualification on the mass of comets.

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jwj

It's ok not to know.

Thank you, and if the internet will cooperate, I will try to have some comment by the end of the day - Evan sent some of his weather down here, complete with more than a foot of fluffy white stuff.

Somewhere on this BB someone defined a scientist as someone we believe when they give us an explanation for an observation that they - the scientist scientist insisted was completely impossible before the fact.

I'm asking you to be scientists: Read the description of the construction of the heat shield, think about how important it is to the health of a hundred million dollar mission. Look at the condition of the heat shield sitting on the Martian surface. Would you make it a little thicker next time?

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jwj

It's ok not to know.

I understood your response in the other thread just fine. But variable G or constant G, the mass of Halley is irrelevant in determining its orbit.

And nothing you wrote in your response to me in this thread explains the Halley observation.

And I'll point out that you also said this in the other thread:

And we do know that Halley, at 28AU, is precisely where it was predicted to be.

My question is this: If G varies enough to lead to a 14% error when calculating Mars' mass, how is Halley right where it's predicted to be at 28AU?

I doubt you can make any engineering decision based solely on how the heat shield "looks" from a few preliminary images. That is why they are spending time examining it with Opportunity.

At the 1st anniversary press conference on Jan 3rd, it was mentioned that the heat shield did a "belly flop" on the surface, hitting pretty much at a flat angle. The shield broke in two pieces and got turned inside out. What looks to be the outside of the shield is really the inside part. Your assertion that the ablative material burned down to the rivets is not correct.

When you read the post-landing analysis paper you will see that , for the parameters they've been able to reconstruct, the values fell within predicted ranges. This would seem unlikely if they had a 14% error in Mars' mass.

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"A mystic is a person who is puzzled before the obvious but who understands the nonexistent." -- Elbert Hubbard

Don't you see the internal contradiction in your own argument? If mass is TOTALLY irrelevent to orbital calculations, How does a 14% error in the Mass of Mars have anything to do with the orbit of Halley's comet? Mass is important, and if the mass of Haley's comet has been underestimated, the fine structure of its orbit is off as well. (This is why you cannot keep time with a pendelum clock on a boat.) Get beyond your sophomore physics!

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jwj

It's ok not to know.