Potential Threat to the Huygen Mission

[Elias]

14 percent greater mass is a great big deal if your engineering margin is 15-20%

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?

[Evan]

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.

[Hamlet]

Are you serious? The above quote is in relation to the temperature of Mars being a bit higher that expected. There's nothing about "residual heat" from entry. You're inventing solutions to non-existent problems.

You are right, there is no mention of residual heat, but that is the whole point of this thread. Every Martian landing parachute deployed late*, and every time it was because of "High down drafts" or "Martian wind storms", and so did the parachute of the Galileo Jupiter probe. Too much coincidence.

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?

The report about Spirit being too hot was just a day or two after landing - I keep complaining about the lack of detail in the NASA press reports because it it so difficult to draw any conclusions other than the those hand-fed to us by those who are "amazed, by the unexpected perfectly puzzling", results.

If Spirit's heat shield looked anything like Opportunity's, there was much more residual heat than expected and it could have contributed to the heating problems for Spirit's electronics - Sorry, but it is a little hard for me to fathom that a 'warmer than expected' atmosphere alone could be the culprit. It's not like Spirit was stuck in the rear window of a hatchback.

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?

In the thin air of Mars, conductive heat transfer is limited, the residual heat acquired during entry has to be radiatively dissipated and that takes time. I wish they would publicly report exactly when the electronics were overheating, and by how much. I would have found statements like "we put too warm of a winter coat on Spirit" patronizing when I was in grade school. NASA's Reader's Digest approach to science gags me. (It must be very difficult trying to coach everything in words that will be not offend the intellect of Washington.)

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?

Both the Global Surveyor and the Mars 0rbiter spent months carefully air braking, trying not to generate too much heat. There are all kinds of indications (in the remarks of the principles), that they were 'puzzled and amazed" by the amount of heat they had to dissipate.

*After watch Spirit fall, they forced the deployment of Opportunity's parachute higher in the atmosphere. It still landed at about the same velocity - 20m/s, 12m/s of which they assigned to a horizonal vector.

Here is a list of all missions to Mars by both the United States and Russia. Very few of the failures came during the landing phase. The ones that were are fairly well understood. Your "fourteen percent error" hypothesis explains nothing.

On your list I can count at least four landers where contact was lost for unknown reasons. They think the Air Bags exploded when Beagle hit, Mars 3 plowed into Mars at 61m/s and managed to send two minutes worth of garbled data. There is some evidence the Polar Lander also may have plowed into Mars, but a new crater spotted by intellegence imagers appeared to be ‘much to large’ to have been the Polar Lander at the expected velocity, even though it is in about the right place, if the Polar Lander failed due to a heat shield failure. (The most probably cause entertained by NASA was "generation of spurious signals when the lander legs were deployed during descent", causing the engine to shut down prematurely, but that does not explain why both of the independent probes also failed.

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?

The one thing the Russian and American failures have in common is they were working with narrower engineering margins than the successful mission, so yes, 14 percent greater mass is a great big deal if your engineering margin is 15-20%. Spirit and Opportunity landed at ~20m/s when they were expecting 14. They were designed to survive at up to 24m/s, so they survived.

...it is highly probable the engineers are scratching their heads, wondering why the remaining composite is so thin.

Oh really? Have you become a mind reader, cause I don't see where in the world you got that from?
…When did you become an authority on what heat shields should or should not look like?

:wink:

Do you know of a mission scientist actually stating that the heat shield was abrated more than they anticipated it would be?

If I were a mission scientist, I would be telling you that I am amazed and puzzled by the perfect performance of the heat shield :roll:

edit - Replacing Pathfinder with the global surveyor...gad!

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

[Evan]

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.

[Wolverine]

Weekly World News

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.

[Jerry]

Both the Pathfinder and the Mars 0rbiter spent months carefully air braking, trying not to generate too much heat.

Try to keep your facts straight if you want folks to actually take you seriously.

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).

...Too bad your info is off. First, the air bags exploding is only one of the hypotheses for the failure of the probe...not the targeted theory.

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

Second, Mars 3 lasted all but 20 seconds on Mars. It made a soft landing according to the engineers but only returned one image before ceasing communications.

Mars 3 impacted the surface at a reported 20.7 m/s at approximately 45 degrees S, 158 degrees W, at 13:50:35 UT. Shock absorbers inside the capsule were designed to prevent damage to the instruments. The four petal shaped covers opened and the capsule began transmitting to the Mars 3 orbiter at 13:52:05 UT, 90 seconds after landing. After 20 seconds, at 13:52:25, transmission stopped for unknown reasons and no further signals were received at Earth from the martian surface. It is not known whether the fault originated with the lander or the communications relay on the orbiter.

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”.

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?

...the aeroshell is made out of an aluminum honeycomb structure sandwiched between graphite-epoxy face sheets. The outside of the aeroshell is covered with a layer of phenolic honeycomb. A phenolic compound is made from benzene and is typically used in various plastics, disinfectants, and pharmaceuticals. This phenolic honeycomb is filled with an ablative material (also called an "ablator"), which dissipates heat generated by atmospheric friction.
The ablator itself is a unique blend of cork wood, binder and many tiny silica glass spheres. It was invented for the heat shields flown on the Viking Mars lander missions 25 years ago.

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.

If I were a mission scientist, I would be telling you that I am amazed and puzzled by the perfect performance of the heat shield

Well hell, given that they simulated it and predicted that well is a pretty good indication that they were doing something right. If you need a 30% margin of error in engineering then you shouldn't be an engineer.

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.

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.

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.

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?

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.

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

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.

[Evan]

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

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.

[R.A.F.]

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.

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.

[Hamlet]

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.

[Tassel]

so yes, 14 percent greater mass is a great big deal

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.

[Jerry]

so yes, 14 percent greater mass is a great big deal

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.

So, Jerry and Lunatik, how do you account for the fact that Newton/Kepler accurately predicted the position and velocity of Halley, 28AU from the sun?

…The mass of Halley, let alone the change in mass of Halley is insignificant compared to the mass of the sun. A change in mass of Halley would not measurably change its orbit.

True, but only to first order: (M1>>M2) If you are trying to calculate the mass of Halley's comet, you would need be looking at the second order effects, and this is where varying the "inertial field capacity" effects would come into play.

I'm not trying to calculate Halley's mass. I don't see how the mass of Halley is relevant. If it is in the orbit predicted by Newtonian gravitation then Newtonian gravitation holds under the conditions tested.

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:

Wild 2, the first comet we observed close-up produced some peculiar surprises: It out-gassed from what appear to be vents on both sides of the comet, and it looked very much like a carbonaceous chondrite. These are organic filled chunks of friable iron and nickel, not blocks of ice. If comets are metallic, they are four two ten times heavier than we think they are.

The fact that Wild 2 outgassed from the side opposite the sun indicates a very high thermalconductivity - the thermal conductivity of metal, not frozen water.

If comets are iron and nickel rich, they weigh much more than we have calculated, and should not decelerate nearly as quickly as they do. Therefore their orbital track could actually confirm, rather than nullify one of these theories.

Wild 2 is scheduled to parachute, not plow, into the Utah Desert in January of 2006. It has samples of whatever peppered Wild 2 as it flew in the wake of the comet. If this includes metallic dust consistent with meteroites (as I think it will) this will be quite enlightening, and I plan to be there.

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.

[Jerry]

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

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.

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.

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?

[Tassel]

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:

First, you are correct, if Halley behaves exactly as predicted, we are out to lunch.

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?

[Hamlet]

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?

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.

[Jerry]

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:

First, you are correct, if Halley behaves exactly as predicted, we are out to lunch.

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?

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!

[Evan]

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 (sic) pendelum clock on a boat.) Get beyond your sophomore physics!

??????????????

Comet??? Fine Structure??? (did you actually mean to refer to the Fine Structure Constant? 1/137) Time to cut back on the funny tobacco.

This is why you cannot keep time with a (sic) pendelum clock on a boat

You can't keep time with a pendulum clock on a boat because the clock rocks with the waves. Hence the development of the balance wheel escapement.

....sophomore physics....

So, you are implying that they first teach you wrong physics and then later (if you last that long) correct that intentional mistake? Or did I misunderstand your intent?

[Jerry]

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.

I am aware the heatshield has been turned inside out. (I should have mentioned that) The shiny surface is the inside, the blackened portion with the honeycomb structure is the outside - you might not be able to see the honeycomb without good resolution. The piece that has broken free has the ablative surface towards the viewer. (there are not any rivets, the two pieces were bonded together), and you can clearly see much of the metallic base where there should still be ablative material: This heat shield should not have been charred right down to the base, but it is. You can tell because bonded layers would not have broken free from the bases, there would have been more splintered remnants and little if any exposed surface. Authority? FWIW I spent about six years working with bonded ablative composites in very high temperature, high flow rate applications, including accessing predicted verses observed results.

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.

Are you reading the same report I am? Better read beyond the summary, because the data do not support the summary

First: They haven’t even included the most relevant data: the reconstructed Peak Heating Rate, Peak Stag Pressure, Total Heat Load, Mach Number – They haven’t even included the Time from entry. What kind of a description of the entry is that? Why are these numbers not included in the report. Why don’t they tell us how long it took the craft to hit the ground compared to the time expected? What kind of a report is this :-?

Second, look at the ship attitude data:

Spirit Hypersonic :
_________________________Expected 3-sigma Reconstructed
Attitude @ Peak Heat Rate deg 0.6 ______0-2.2____ 1.8


Spirit Parachute Deployment
--------------------Expected 3-sigma Reconstructed
Attitude (deg)--------_.1 ---_0-4.9---------_7

Opportunity Hypersonic:
--------------------------------Expected 3-sigma Reconstructed
Attitude @ Peak Heat Rate deg__0.6_ 0-2.1______ 2.1

Opportunity Parachute Deployment.
--------------------Expected 3-sigma Reconstructed
Attitude deg _______1.0 ___0-4.4____8

The maximum expected Craft attitude was 4.4 degrees, but they were both tipping 7 or more degrees when they deployed their parachutes. What does that mean? Both craft were reasonably close to their targets, so It is unlikely that they entered the atmosphere at the wrong angle.

Without the Peak Heating Rate, Total Heat Load, Mach Number and Peak Stag pressure; your guess is as good as mine, but if these numbers are high, it could mean the Heat Shield was distorted during entry and it burned around the edges.

The Report Summarizes:

For both the “Spirit” and “Opportunity” entries, the time of parachute deployment was later than predicted because a lower density atmosphere was experienced. Based on preliminary atmosphere reconstruction estimates, approximately an 8% lower density profile (correlating to roughly a 1-ó low profile) was encountered in the maximum deceleration region during the “Spirit” descent, while approximately a 12% lower density profile was encountered during the “Opportunity” descent. This greater reduction in the density profile for “Opportunity” (as compared to “Spirit”) is consistent with the observed later time of parachute deployment.

Lower atmospheric density than predicted? Later parachute deployment than expected by almost three sigma? That is the same thing they concluded with both Viking Landings, and suspected with Beagle. What is wrong with the atmospheric modeling?....I just found a NASA Pathfinder Report:
http://techreports.larc.nasa.gov/ltr...-2004-5092.pdf

The descent rate on the parachute was somewhat higher
than expected, but well within the design envelope.

Somewhat? Nice technical term, NASA. So add Pathfinder to the "falling too fast" list. How much coincidence is too much? I am running out of hair to pull out :roll: I could make another bet: I'lll bet a steak dinner Spirit, Opportunity, and Pathfinder all landed quicker than expected, and long of the target.

Even more ominous is this paragraph:

The landing locations for both “Spirit” and “Opportunity” were within the pre-entry predicted footprint ellipses. “Spirit” landed 13.4 km downrange from its predicted landing location, while “Opportunity landed 14.9 km downrange from its predicted landing location. The reconstruction work is ongoing in order to gain a better understanding of what transpired during the “Spirit” and “Opportunity” landings.

Anyone who has written a final report, where the results came up short of expectations, is familiar with this canned euphemistic approach, and what it really says is: WE HAVE NOT INCLUDED THE PEAK HEATING RATE, MACH NUMBER, PEAK STAG PRESSURE, TOTAL HEAT LOAD AND TIME TO LANDING BECAUSE WE DO NOT UNDERSTAND AND CANNOT EXPLAIN THIS DATA

[Tom Ames]

Jerry,

I'm just curious, and I'll understand if you don't care to answer this question:

what is your belief (if any) on the validity of modern ("Darwinian") evolutionary theory?

Thanks!

[Tassel]

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?

I did not say "mass is TOTALLY irrelevant to orbital calculations". I said the mass of Halley is irrelevant. This is because the mass of Halley is so small when compared to the mass of the sun, that the mass of the sun effectively becomes the only mass we need to worry about in determining Halley's orbit. We covered this in the other thread, Jerry.

So, I'll ask the same question again: If G is variable based on distance from the sun in the way you describe (ie: that we've miscalculated the mass of Mars by 14%) how can Newtonian physics perfectly predict the location of Halley's comet at 28AU?

I'll also point out again what you said in the other thread:

First, you are correct, if Halley behaves exactly as predicted, we are out to lunch.

[Elias]

The maximum expected Craft attitude was 4.4 degrees, but they were both tipping 7 or more degrees when they deployed their parachutes. What does that mean? Both craft were reasonably close to their targets, so It is unlikely that they entered the atmosphere at the wrong angle.

What do you say it means? Does this verify your theory and how?

Because I am just saying since the atmospheric model didn't give correct predictions in general (denser atmosphere expected), deviations would be observed in anything that atmospheric dynamics is involved.

What is wrong with the atmospheric modeling?....

Nothing. It is just difficult. And sometime ago, I have written this to you:

Do you think that we have perfect understanding of the Martian atmosphere with just a few landing attempts? How do you expect scientist to have perfect knowledge on density and temperature profiles etc. about an atmosphere that has barely been studied? And on top of that, how do you expect them to understand the variabilllity of an atmosphere? You think is easy? NO! You think an atmospheric state is easily predictable? NO! You think that atmospheric densities are definded just by gravity? NO! What about winds, temperatures, latitude, topography, any other type of event that could disturb the atmosphere locally (dust storms)?

There are hundreds of reasons that an atmospheric state cannot be predicted. Especially for landers, where the accuracy in velocity has to be less (or not much more) than 1 m/sec during landing, those differences are much more important, but even more difficult to avoid. Maybe it is impossible. That is why the best thing that can be done, together with some good atmospheric physics, is a lot of statistics, so that margins on density profiles (that are the most important for landers), can be defined. In this case the necessary margins will be applied in mission design.

Now, I am not really sure whether any of these margins were available for the Russian landers (although you forget ot mention that Mars 3 landed within a dust storm), Viking, Pathfinder etc. Maybe they were available for Beagle, but you might know that Beagle had the worst mission design ever.

And let me also add that that the MER landers had retrorockets to control the impact velocity - the fact that they used them is because enineers were aware of the uncertainties in the Martian atmosphere models. And finally, that at the last COSPAR I became aware of a project called: Mars International Reference Atmosphere (MIRA) Development - a project still underway that could probably support future mission. The Martian atmosphere is not a problem solved - but this is not due to the wrong understanding of gravity.

The landing locations for both “Spirit” and “Opportunity” were within the pre-entry predicted footprint ellipses. “Spirit” landed 13.4 km downrange from its predicted landing location, while “Opportunity landed 14.9 km downrange from its predicted landing location.

These are distances from the center of the landing ellipse. The landers actually landed within the landing ellipse - nothing strange with that. It is just always better to try to improve the accuracy and understand why they didn't land at the most probable spot. Pinpoint landing will be a requirment for future missions and therefore they have to understand as much as possible about landings on Mars

[Jerry]

So, I'll ask the same question again: If G is variable based on distance from the sun in the way you describe (ie: that we've miscalculated the mass of Mars by 14%) how can Newtonian physics perfectly predict the location of Halley's comet at 28AU?

And I will answer again: To first order, and r^2 gravity and an r^2 gravity with a logrithmic diminishing inertial component will predict the same orbit, as long as M1>>M2. To first order, Haley's orbit will not mathematically differentiate between these two expressions for gravity:

The acceleration of the Pioneer probes towards the Sun coincides exactly with the lose of 'inertia': This is fundamental to this alternative hypothesis of gravity within observational limits. At higher levels of differentiation, second order effects come into play and these are a function of the mass of Halley's comet and other objects like the "Oort cloud". We only know Pioneer 10 and 11 were not following perfectly elliptical orbits because we could us doppler and radar to fix the position of Pioneer with much more accuracy, and this in tern allowed us to use the Pioneers to "accurately" predict the masses of the outer planets and their moons. But these predictions are wrong, and Huygens is going to fall like a rock.

So, you are implying that they first teach you wrong physics and then later (if you last that long) correct that intentional mistake? Or did I misunderstand your intent?

They simplify.

The maximum expected Craft attitude was 4.4 degrees, but they were both tipping 7 or more degrees when they deployed their parachutes. What does that mean? Both craft were reasonably close to their targets, so It is unlikely that they entered the atmosphere at the wrong angle.

What do you say it means? Does this verify your theory and how?

The attitude, once the craft has entered the atmosphere and been slowed to subsonic speeds, is primarily dictated by the shap of the the vessel - even if the cross wind is very strong, the aerodynamics dictated less than 4 degrees of pitch and wobble according to both of the dynamic models, and this was allowing for all expected atmospheric conditions. But Spirit and Opportunity deployed at 7 and 8 degree pitches, respectably. This is a strong indication the heat shields were seriously deformed during atmospheric entry. The rest of the thermal data could confirm this: Why, a year after the fact, have they not released it?

What is wrong with the atmospheric modeling?....

...There are hundreds of reasons that an atmospheric state cannot be predicted. Especially for landers, where the accuracy in velocity has to be less (or not much more) than 1 m/sec during landing, those differences are much more important, but even more difficult to avoid. Maybe it is impossible.

Are you sure? Think about it: The Martian atmosphere has far less kinetic energy in it due to less solar heating. On Earth, we find strong shear forces – down drafts, when water vapor cools and condenses, releasing energy into the atmosphere. This cannot happen on Mars, and even though the winds may be have high linear velocity, it is thin.

After about three Gemini flights we were consistently parachuting capsules within five kilometers of the target on earth. Even if the Martian atmosphere is difficult to characterize, the error should be random, we shouldn’t be sitting around wondering why every single mission was caught in a down draft. I will concede that in a landing during a Martian night the atmosphere may be contracting downward, but not during the day.

That is why the best thing that can be done, together with some good atmospheric physics, is a lot of statistics, so that margins on density profiles (that are the most important for landers), can be defined. In this case the necessary margins will be applied in mission design.

I agree, to some extent, but obviously if the physics are wrong, a better solution can be found. Think about what statistical solutions imply: You roll the dice a whole bunch of times, and you can figure out the solution probabilities without knowing the geometry of the dice. It does not require a known causality or a known physical mechanism, only a knowledge of prior conditions. We can do better.

I'm just curious, and I'll understand if you don't care to answer this question: what is your belief (if any) on the validity of modern ("Darwinian") evolutionary theory?

It is a relevant question because scientific philosophy is at the very heart of this argument. Darwin made observations, bumped them up against the prevailing thought of the time, developed seven hypotheses and drew well-reasoned conclusions. In the last one hundred and fifty years three of his theses have been disproved, but the remaining four have proven outstanding. We find supportive evidence for the balance of his thesis in everything from the fossil record to our own cluttered DNA. But we cannot be complacent. We should always question.

I think the evidence at hand suggests the physical community took a wrong turn one hundred years ago: Einstein found a solution to the Michelson Morley experiment, but it was not the right one. It was close, and the mathematical structure we have built around the Einsteinian solution has proven to have good predictive power, but on cosmic and extremely small scales they do not work.

The incorporation of “Dark Energy” in the cosmic solution is the apex of this failure: Our cosmologists are telling us we know nothing about 96% of the mass fraction of the universe. I am 96% confident the model is wrong, and we will see this again in the plight of the Huygens probe.

Edit: clarification on Pioneer anomally.

[Lunatik]

The acceleration of the Pioneer probes towards the Sun coincides exactly with the lose of 'inertia': This is fundamental to this alternative hypothesis of gravity within observational limits. At higher levels of differentiation, second order effects come into play and these are a function of the mass of Halley's comet and other objects like the "Oort cloud". We only know Pioneer 10 and 11 were not following perfectly elliptical orbits because we could us doppler and radar to fix the position of Pioneer with much more accuracy, and this in tern allowed us to use the Pioneers to "accurately" predict the masses of the outer planets and their moons. But these predictions are wrong, and Huygens is going to fall like a rock.

Do you mean, conceptually, that the loss of 'inertia' is actually the loss of 'inertial velocity'? This is indeed what seems to happen, if using a constant momentum, p = mv. I would think for greater m (greater 'inertial mass'), we get lower v (lower 'inertial velocity'), which would match the idea of lower 'acceleration velocity' for greater G (at greater distance from the Sun), if I am understanding this correctly. This seems to be happening to Pioneers. However, greater 'inertial mass' means greater gravitational response, hence possibly higher re-entry velocity to Titan?

Just trying to get meaning of 'inertia' straight in my own head, since this may be important for future observations. Here's a carry over from another thread by "iron4", dark matter clumps demonstrated which seems to support greater G, viz. Dark-matter, per link shown. ... still hunting for clues. 8-[

[Tassel]

And I will answer again: To first order, and r^2 gravity and an r^2 gravity with a logrithmic diminishing inertial component will predict the same orbit, as long as M1>>M2. To first order, Haley's orbit will not mathematically differentiate between these two expressions for gravity:

Well, first of all, I cannot see the "two expressions for gravity". Either you didn't post them correctly, or I for some reason can't see them.

Second, if I understand you correctly, you seem to be claiming that a variable G hypothesis predicts essentially the same orbit for Halley as Newton does. This is incorrect. At least it is if, as you claim, Newton is off by as much as 14% at Mars. Maybe you need to show some math. Can you show where you got the 14% figure? Can you show what that figure should be at Saturn? At the orbit of Neptune (where Halley is)?

The acceleration of the Pioneer probes towards the Sun coincides exactly with the lose of 'inertia': This is fundamental to this alternative hypothesis of gravity within observational limits. At higher levels of differentiation, second order effects come into play and these are a function of the mass of Halley's comet and other objects like the "Oort cloud".

You're saying two things here:

1. That the Pioneer probes are affected by this "lose(sic) of 'inertia'", but that Halley is not.

2. That "second order effects" are affecting Halley. Ok, maybe so. But are you then claiming that these "second order effects" are causing Halley to behave exactly as Newton predicts when it otherwise wouldn't? Because you can't deny the observation that Halley is behaving as Newton predicts. Can you give examples of these "second order effects"? What effect does the Oort Cloud have on Halley, exactly? What "second order effects" are affecting the Pioneer probes? Does the Oort Cloud effect them as well?

Here are some more observations for you to ponder:

Are you aware that several Mars spacecraft, I believe starting with Mariner 6 carried experiments specifically designed to measure the acceleration on the spacecraft due to Mars gravity? From NASA's Mariner Mars Missions page:

"A celestial mechanics experiment was also included in the mission, which, by analysis of the extremely accurate tracking data of the paths of the spacecraft, provided a precise measurement of the mass of Mars."

The most recent one I could find was on Mars Global Surveyor. From NASA's MGS Radio Science Investigations page:

"The Radio Science Investigations on Mars Global Surveyor have two distinct objectives. The first is to map the planet's gravitational field and the second is to measure the atmospheric pressure and temperature in the polar regions"

Note that these experiments directly measured the acceleration of the spacecraft due to Mars' gravity. So we do in fact have experimental evidence of the strength of Mars' gravitational field, independent of predictions by Newton.

As another note, you can also find position and velocity data for MGS here. With Newton's formulas, simple algebra, and using established values for Mars' mass and radius, you can very accurately predict the velocity of MGS at any time. Can you explain this with your variable G hypothesis?

Furthermore, Cassini itself carries a Radio Science Subsystem which has also been used to measure the effects of gravity within the system. One of the listed scientific objectives for the RSS package is "To improve estimates of the masses and ephemerides of Saturn and its satellites".

Questions:

1. When you talk about "second order effects" on Halley, are you suggesting that these effects are causing Halley to obey Newtonian gravitation when it otherwise wouldn't?

2. How do you explain the lack of anomalous results from experiments conducted by Mariner 6 & 7 (and others), Mars Global Surveyor and now Cassini itself?

[Tassel]

Oh and Jerry, one more thing. You did say this in the other thread:

First, you are correct, if Halley behaves exactly as predicted, we are out to lunch.

In your responses to me here you don't seem to be denying that Halley is behaving as predicted. So are you not "out to lunch"?

[papageno]

But in this case, you have to justify why the Sun is so special. Why doesn't G depend on the distance from other massive objects, such as Jupiter?

If you carefully read my posts on the first page of this thread, this is just what I said: The relationship of the moons of Jupiter and Saturn with their host planet follow the same law.

This is why I cannot make good estimates for the masses of these planets: I know the mass of the moons of these planets was instrumental in determining the mass of the system. I do not know exactly how these masses were determined, and my guestimates for Jupiter and Saturn may be off as much as 100%.

The same is also true of Uranus and Neptune, but to a lesser extent.

So, the case you support is:

If G depended on distance, the force of gravity would not follow an inverse square law anymore.
So, the orbits of planets, comets, and probes would no longer be elliptical (there would be no such thing as Kepler's laws).

Unless you assume that the masses "re-adjust" themselves so that the force of gravity is exactly an inverse square law.
But in this case, there would not be any anomaly in the orbits of the probes.

(I have been away for three weeks. Sorry for the delay.)

[Astronomy]

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?

Have you ever been in charge of or known someone who was in charge of payload management on a space mission? Do you know how everything is made to the specifications of being just enough and not anything more? If the heat shield worked, no one is going to reengineer it. That's the nature of probe missions.

[Jerry]

The (above) questions are excellent, and deserve descent answers – I can’t get to them all tonight, but let me try to answer some of Tassels:

Assume Haley’s comet is out-gassing randomly, lossing (sic) mass equally in all directions and changing density as it speeds away from the inner solar system, passing close to each planet. This would not change our observation of its orbit. But if Haley lost 15% of its mass by the time it reached Mars, and 63% by the time it reached Jupiter, and we did not know it, then when we studied the minor perpetrations Mars and Jupiter caused in the path of Haley’s comet, we would underestimate the mass of Mars and Jupiter by the amount of mass Haley lost.

I think that is exactly what did happen with the Pioneer 10 and 11. EXCEPT they were not losing mass, they were losing ‘inertial capacity’, just as all objects in our solar system do with increasing distance from the Sun. The loss in inertial capacity is small – equivalent to an acceleration of 10^-10m/s^2, but it is enough to throw off our calculations of the masses of the planets by a wide margin.

Remember, this is a totally different concept of gravity and inertial effects, but the only one I can find that has a chance of modeling both the rings that form in supernova debris and the curvature of gas jets near active galactic nuclei.

2. How do you explain the lack of anomalous results from experiments conducted by Mariner 6 & 7 (and others), Mars Global Surveyor and now Cassini itself?

The loss of “inertial capacity” I have described applies to every mission, not just the Pioneer probes. The Mariner flyby determined the mass of Mars based upon the change in Mariners orbit around the sun. Any measurement deviations that use just ranging and/or accelerometer data relative to the Sun will have the same system errors.

It is only if you have a combination of radar and accelerometer data not relative to the Sun that the truly puzzling results emerge. Check out this report on Mar's Pathfinder:

Flight reconstruction of the entry using MPF flight accelerometer data revealed that Pathfinder decelerated faster than predicted based on the estimated value of the MPF parachute [drag coefficient] of 0.50; a value which was determined from low altitude Earth flight tests and wind tunnel data during the development of the MPF parachute (see Ref. 3). An explanation of this underperformance of the MPF parachute system from that which was predicted is still not known.

And this one on Viking 1 and 2

Attitude rates observed on both VLCI (Viking 1) and VLC2 (Viking 2) in both pitch and roll exceeded the predicted maximum rates by a factor of 2 after maneuvers and before 0.05 g.

Predicted pitch –0.85 Observed: Viking I :-1.81, Viking II: -2.08
Predicted yaw 0.85 Observed: Viking I: -1.09 Viking II: -2.07

Both vehicles trimmed at higher negative angles of attack than expected and there had higher L/D than planned. Base cover heating exceeded expectations but was acceptable. Real Gas effects caused several parameters to vary from predictions based on wind tunnel tests using air, but these variations did not have a significant effect on the missions.

Dynamic pressures derived from the flight-measured stagnation pressure differ significantly from those derived and used in LTARP[simulations]. The LTARP values are based on accelerations measured in flight and aerodynamic characteristics, particularly the axial force coefficient, (CA) determined from wind-tunnel tests using air.

Flight data points show sizable percentage errors at the higher and lower extremes of the altitude range…It is in the low range area of operation that the unexpected discrepancy occurs…

P35…the angles of attack and lift-to-drag ratios for both VI an dVL2 were greater than predictions…The causes of higher trim angles of attack on both vehicles cannot be positively identified but are believed to be some combination of off-nominal cg [center of gravity] position and out-gassing/ablation effects.

P37… Because flight trim angles were higher, a slight reduction in Ca would be expected. However, the figure shows that flight axial force coefficients were significantly higher . This was particularly true early in the entry while the Mach number was greater than 10.

…Very early in the entry near the 0.05-g point, accelerations are very small and the accuracy of the force coefficient calculation is poor. No obvious explanation is available for the high Ca values later in the entry between Mach 2 and 5.

…during the early high-speed portion of the entry, the pitch stability was.... greater than the prediction derived from the air wind-tunnel tests.

There are two choices here: the gas laws are different on Mars or we have underestimated the mass of Mars and we do not understand gravity.

(Since the attitude on these missions was also more than three sigma out of wack, I need to withdraw my conclusion that the attitude anomaly on the rover missions was primarily due to heat shield burn through: It was more likely due to the much greater than expected attack angle and horizontal velocity during reentry...I need more data!)

How do you explain the lack of anomalous results from experiments conducted by Mariner 6 & 7 (and others), Mars Global Surveyor and now Cassini itself?

Global Surveyor is getting some very funky numbers – the moment of inertia calculated using the density profile they have made for the core cannot be reconciliated with the mass distribution near Mar’s highest peaks.

Cassini experienced funky gyro behavior near Jupiter just like Galileo did. (And Evan, they are big gyros, they are actually mass stabilization wheels used to stabilize the platform for photography.) The Doppler signal during the swing by Pheobes was expanded more going in and stretched coming out than predicted, which is just what would be expected if Pheobes is more massive.

Mostly what we hear from Cassini mission control is everything is perfect and puzzling, but don’t worry, the mission scientist will figure everything out and let us know there is still order in the universe.

Oh and Jerry, one more thing. You did say this in the other thread:

First, you are correct, if Halley behaves exactly as predicted, we are out to lunch.

In your responses to me here you don't seem to be denying that Halley is behaving as predicted. So are you not "out to lunch"?

You need to read John Anderson’s papers on the Pioneer probes – they detail all the forces that have to be considered in determining the anomalous acceleration of the Pioneer probes.

1. When you talk about "second order effects" on Halley, are you suggesting that these effects are causing Halley to obey Newtonian gravitation when it otherwise wouldn't?

We do not know the velocity and direction of Haley’s comet with nearly enough precision to look for effects of this magnitude, we don’t know where the orbit peaks, and even if we did, we don’t know how much it is being disturb by Kuipler Belt and Oort Cloud objects (we can discount these effects as being causal in the Pioneer acceleration because we were able to monitor the Doppler shifts closely enough to know it is a persistent, continuous force.) Only since the Viking Mission have we had enough information to come up with an explanation for the variance in Neptune's orbit, but on one of the Cassini status reports, they decided not to fly quite so close to one of the moons, because, as near as I can tell Cassini is getting different mass values than those extrapolated from the Voyager mission.

As another note, you can also find position and velocity data for MGS here. With Newton's formulas, simple algebra, and using established values for Mars' mass and radius, you can very accurately predict the velocity of MGS at any time. Can you explain this with your variable G hypothesis?

Yes! MGS is in orbit around Mars, and under the influence, primarily, of Martian gravity, but remember the ‘inertial capacity’ varies from the planet the same way is does with increasing distance from the Sun, exponentially. So while the Global surveyor is in orbit, everything seems normal: Except when it passes over massive features, and this is why they cannot conclusively determine the moment of inertia of the planet.

Like Lunatik, I am still searching. I hope I can come up with better answers than I have today. With the evidence I have in hand, I am sticking with the prediction: Huygens has little chance of surviving the entry phase. If it does, and is able to relay data, it will descend as if the force of gravity is increasing exponentially. If the small Parachute is deployed before it strikes the planet, it will fall like a rock.

[papageno]

1. When you talk about "second order effects" on Halley, are you suggesting that these effects are causing Halley to obey Newtonian gravitation when it otherwise wouldn't?

We do not know the velocity and direction of Haley’s comet with nearly enough precision to look for effects of this magnitude, we don’t know where the orbit peaks, and even if we did, we don’t know how much it is being disturb by Kuipler Belt and Oort Cloud objects...

Please provide some quantitative estimates for your "not nearly enough precision" and for these "second order effects".
Predicting that the comet returns every 76 years and being able to send a probe (Giotto, if I recall correctly) to meet it, is not too bad.

[Tassel]

But if Haley lost 15% of its mass by the time it reached Mars, and 63% by the time it reached Jupiter, and we did not know it,

You can't be serious. Where is this mass going? And somehow Halley re-accumulates this mass on the way back? And all this happens in such a perfect, yet coincidental way, that it mimics Newtonian gravitation? I'm sorry but that's just absurd.

The Mariner flyby determined the mass of Mars based upon the change in Mariners orbit around the sun.

That's one way to put it. It's much simpler to say it measured the rate of acceleration of the spacecraft.

It is only if you have a combination of radar and accelerometer data not relative to the Sun that the truly puzzling results emerge. Check out this report on

All the NASA info you quoted described anomalies during entry. Once you enter the atmosphere, there are plenty of other factors besides gravity that can affect the descent. Can you honestly say that data gathered while Pathfinder was parachuting to the surface of another planet is a good test of gravity? I'd love to see the error bar on that experiment.

We do not know the velocity and direction of Haley’s comet with nearly enough precision to look for effects of this magnitude, we don’t know where the orbit peaks, and even if we did, we don’t know how much it is being disturb by Kuipler Belt and Oort Cloud objects

We know the velocity and direction of Halley's with an amazing amount of precision. As pointed out in the other thread, we got it in the eyepiece of a telescope at 28AU. That's staggering accuracy.

But you know what? This whole debate is so silly, I missed the obvious. Jerry, you're claiming that G varies with distance from the sun so we're underestimating the mass of Mars, etc, which is causing our landers to fall faster due to higher than expected gravity.

There is a fundamental problem with this hypothesis. We have satellites in nearly circular orbits around Mars, and we know the precise velocity and altitude of those satellites. We don't need to know the mass of Mars or Newton's gravitational constant to figure out the acceleration due to gravity at Mars.

Orbital velocity is calculated by the following formula:

v = Sqrt((G*M)/R)

G = Gravitational Constant
M = Mass of Mars
R = Distance from center of mass

From the MGS data, we know v and we know the altitude of MGS. We also know the radius of Mars. So take the last data point on the MGS list, from 12/12/04:

v = 3.33359 km/s = 3,333.59 m/s
R = Radius of Mars + Altitude of MGS
R = 3.3970 x 10^6m + .4352 x 10^6 m = 3.8322 x 10^6 m

Flip the formula and solve for G*M:

G*M = v^2 * R
G*M = 1.1113 x 10^7 * 3.8322 x 10^6
G*M = 4.2587 x 10^13

Note that we don't care what G and M actually are. We know the product of the two, which we can use to calculate g at the surface of Mars (or any other altitude above Mars):

g = G*M/R^2
g = 4.2587 x 10^13 / 1.1540 x 10^13

So...by our calculations:

g(surface of Mars) = 3.6904 m/s^2

And the accepted value for g on the surface of Mars? 3.71 m/s^2

Of course, we could have used Deimos or Phobos to run these numbers also. Just like you can use any of Saturn's moons to compute g for Saturn...and we don't need to know the mass of Saturn or the value of G to do it.

So there it is. We've used experimental data to confirm our predictions. These are the same formulas we use to keep satellites in Earth orbit. And we've just shown that they work to keep satellites in Mars orbit. I think it's pretty clear that we don't need to be guessing at what heat shields should look like to determine if we know how fast things fall on Mars. We've had satellites "falling" around Mars for over 30 years.

Can you explain how MGS stays in orbit if the surface g of Mars is greater than the accepted 3.71 m/s^2

[R.A.F.]

I am sticking with the prediction...

Well, that's really a shame, Jerry. You've "bet" all your "money" on Huygens failing...and if it doesn't, your credibility (as it were) will be ZERO!

Are you prepared for that?