I have updated my GG Earth kmz of Phoenix EDL. Now, there are the principle events along the path. I enjoy a lot to put in some information and picture into the "bubbles" .
http://www.db-prods.net/blog/?p=362

Now I'm wondering, would the backshell and parachute have hit the dirt just after Phoenix landed? Would that have been detectable?

They've have landed quite some time afterwards, a minute or so ( only 40 seconds to land by Phoenix, and with Phoenix off the backshell, the parachute and backshell have a lot of drag for not a lot of mass ) - and with a comparatively gentle touchdown - certainly not that second peak.

Doug

But the oscillations do not diminish, so no dampening seems to be going on...

I think those wibbley wobbles that persist after landing are a symptom of whatever did these measurements - that's its noise floor.

Doug

Generally, IMUs are pretty stable...unless the frame that they're mounted to isn't. Is it possible that the vehicle was oscillating a bit on the landing legs immediately after landing from any transverse component of the landing vector?

Phoenix EDL Reconstruction 1A

Quality is poor but at least you can see the spacecraft swinging around during the parachute drop.

Any suggestions on how to host a 42MB video with better quality than this? Also any suggestions on cinematography?

As far as terminal velocity of just the backshell goes, I get the following:

drag force=gravity force
(1/2)(Cd)(A)(rho)(v^2)=(mu)(m)/(r^2)

mu=mars gravity parameter=42828.314e9m^3/s^2
A=parachute effective area=109.36m^2
Cd=Parachute drag coefficient=0.63
r=Distance from center of Mars=3380000m
rho=Atmospheric density=0.018kg/m^3
m=backshell mass=110kg

Plugging these all in and solving for v

v^2=2(mu)(m)/(r^2(Cd)(A)(rho))
v=sqrt(2(mu)(m)/(r^2(Cd)(A)(rho)))

The calculation for the fully gassed up system minus heatshield only (m=587kg) gives a terminal velocity of 59.57m/s, which compares well with the observed downward velocity of 55.09. By adjusting rho to 0.021kg/m^3, we get a match for the lander+parachute+backshell system. Now taking these same parameters and putting in the mass of the backshell and parachute only we get a mass of 110kg and a terminal velocity of 23.85m/s

Parachute detatch happened at 948.14m above the landing site. With this vertical velocity, the backshell hits the ground in 39.76s, just before touchdown, which happened 41.065s after separation. Does this make sense? Sure. The lander drops at 55m/s and gaining once it separates, but uses its rockets to slow down almost immediately. It starts with twice the speed of the parachute but slows to 2.5m/s after 30s.

That was really quite nice. I'm humbled to see even a simple animation replaying the actual telemetry like that. I think I can guess which vectors some of the colored arrows were portraying, but would you mind posting them? Very nice. I can't wait to see more.

The white bar has one end at the spacecraft position 1/24 second ago, and the other 1/24 in the future. The orange arrow is non-gravitational acceleration, each meter length is 1m/s^2 of acceleration. The blue, yellow, and magenta arrows describe the local drag frame. The cyan one points in the direction of motion, the magenta one is horizontal and perpendicular to the first, and the yellow one is perpendicular to both and points up as much as possible.

Truly outstanding presentation, Kwan.

I do find myself wishing I could see an image post-'chute-deploy that centers on the chute and not the aeroshell/lander. From the motions of the aeroshell, it's obvious that it's swinging pretty fast under that 'chute. I'd love to watch that dynamic.

-the other Doug

Kwan - Hosting, I can sort for you, no problem. (drop me an email - djellison@mac.com ) It's an AMAZING video...just bloody amazing! What was it rendered in - and where did the models come from -they're very good indeed!

I can imagine tying that into the sort of rendering I did for the those HiRISE DEM animations for a stunning end result!

Doug

Wow ... genius! And the background music gives a nice comparison with the planned sequence of events (those of us who have disected that animation sec by sec or frame by frame would be very well versed in the meaning of the background music )


I should be able to host it for you at the Space Outreach Library. That would be an impressive first file for the library (which is coming soon, I promise ... it is well enough to host files at this moment)

Thanks! I've already got the next two versions in the pipe. One is audio, with the music tweaked to hit the actual events as opposed to planned, and with JPL audio. The next is with a HUD.



Rendered in a modified version of MegaPOV, itself a modified version of PovRAY. Took 14 hours on four cores in two boxes. Models are translated from an Orbiter model by brianj

I was thinking that as well, but when I then look at around 218 seconds before touchdown, there aren't such pronounced wiggles. Would the "noise floor" be different in flight? - I am thinking that it would more likely be some residual movement, but the strange thing is that it doesn't taper off...

On another note: Fantastic animation kwan! - Talk about contributing to the forum!

If you can export to 3DS with animation - hint hint - let me know



Back shell gyro compared to lander gyro - assuming they're separate like MER?

Thirded, fantastic stuff kwan! Regarding cinematography - would it be possible to show the vehicle from different distances, especially as the backward-pointing arrow disappears from the field of view? It's a great way to visualise the accelerations as physical lengths relative to the size of the lander. Also perhaps "cutting" to different camera angles around the time of key events (parachute deployment, backshell jettison etc) might be good? Integrating it with Doug's stuff with surface imagery and relieft would be just too awesome - the only reason I haven't started sending the link to people is the thought that an even better version could be in store...

Just 2c from the peanut gallery, from someone who can only admire the incredible talent around here

Fantastic animation . It's a great work.

On my side, I continue to work on my KMZ file. I've added superimposition of picture to show the ellipse landing site, the MRO of landing site and a vertical projection made by NASA .
The respective scale of the image are a little approximative, but, I believe that it's pretty good.
You must know that you absolutely need the Google Earth software to see these superimposition .



Always here : http://www.db-prods.net/blog/?p=362

Version 1B

This is really fantastic, thank you kwan3217 !

May I humbly suggest, that after landing, it would be great if the video fade out to the real view from the deck of Phoenix, i.e a scroll through the Peter Pan panorama, keeping in sync the sounds of joy from the mission control ?

Many thanks once more for this great work of yours .

So cool, particularly knowing that every wobble is true to life!

One thing--the ground controller at one point mentions that the parachute is "normally deployed at this time" but the animation shows the chute coming out a few seconds later. The animation may be more correct than the ground controller as for that timing, but maybe it takes several seconds after chute deployment for the "signal" to show up in the accelerometer?

In fact, the HIRISE page showing the Heimdall crater image notes that it was taken "just a few seconds after the parachute opened" and "about 13 km above the surface." In the SPICE data, there's nothing unusual happening around altitude 13km, and the first real tug from the chute is seen at around 10.5km altitude.

On the other hand, looking at the Heimdall image, it's hard to believe that the chute isn't already pulling pretty hard on Phoenix.

Given that the heatshield is already some distance from the backshell, yeah - that altitude figure must be wrong.

OR

Perhaps that's when the image started being taken? HiRISE swoops out an image over time...but I don't think it's that long.

Doug

Great animation, many congratulations! Did anyone else feel those Landing Night butterflies take wing in their stomachs again when they heard the soundtrack? Strange for such a gentle piece of music, but now whenever I hear it I really do feel very nervous again, as I have a flashback to watching the EDL animation projected on my living room wall in realtime on Landing Night...

Yes, I did. And the landing commentary still brings a tear to my eye.

I still marvel at the fact it worked, the shear number of things that had to go right in order to land perfectly.
I'd love to see the software flow charts on the EDL sequence.

..and it is amazing to see how rock-steady that powered descent is by the lander. Hardly hardly any wiggling, yawing, slewing, rolling, except for the planned yaw to align with the N-S axis. Just perfect smooth control!

Question about the wobbling when PHX hangs on the parachute: does it pivot around the center of the spacecraft gravity (which seems to be what is animated) or would it pivot around the point where the parachute is attached to the backshell?

I actually think it pivots at or near the center of pressure of the parachute. I am imagining a pendulum with a heavy bob. Even though the center of mass is near the bob, the whole system rotates around the pivot, which may have near no mass at all.

I put the orange arrow in the system for something like this purpose. I hypothesize that at all times while the chute is deployed, the parachute riser is parallel to the orange arrow, which represents the nongravitational acceleration. Nearly all of this is aero force on the chute, the remainder is aero force directly on the backshell. Since the center of pressure of the chute is near or on the chute axis, and since a rope can only support tension, the rope should be parallel to the force it exerts. What interests me is that this says that the wrist movement is actually very small. The orange arrow almost always emerges out of the top of the backshell, its origin is near the center of mass of the lander, much closer to the heatshield, so this is significant. If there was a large wrist movement, the orange arrow would emerge somewhere else, like it does at times during peak deceleration on the heatshield.

Wow, Kwan, that was just great! Watched 1A & 1B, both were delights. Thank you!

Wow wow Kwan. Very nice job.

Doug E. pointed this work out to me today and I have to say that I am very impressed with you and all of the gang. I was not aware that the NAIF data had been released. It is very cool that you can do this work.

As I told Doug, I wish the rules allowed people like me to borrow your skills to help us. I don't know how many times I wish I could post something here and have some of you do some engineering / rendering for me! (the price is right and you all have the"chops" to do this)

Reconstructing & studying how things work (when they do) is the fun part, I am glad that you and Doug and the other UMSF gang have been able to dive in.
Our (small) Phoenix EDL reconstruction team is running behind you (a little) as already they are getting busy on other jobs, but a couple are diving into this data and comparing our sims with this (and the radar) data. One of the aspects of having a bit of "truth" (for a change) is that we can see how far off we are in our ability to predict what can happen during EDL. We will certainly learn something from this, but so far we are collectively happy that it was pretty close to what we expected. (there was a lot of room for variation even in our models). What is especially exciting is that we can compare this "passive, unguided & non-spinning" entry vehicle with our ballistic range data and maybe confirm or update our aero models. Hopefully the team will publish in the coming months.

I sent a link to this thread to the Phoenix EDL gang. I think they are impressed too!

Have fun!

Now back to MSL for me ...

Your fan,
Rob Manning aka MarsEngineer


********
Comments are those of the author and do not represent the views of NASA, Caltech nor JPL.

Well Rob, none of us would be able to do anything if you folks didn't put in that much hard and brilliant work in the first place ...

YES : 5 wheels to you, MarsEngineer, to ALL what you did since MPF and for all new landing techniques you found and for the technologies you developed and tested so well on Mars !!!!
Should there be a Nobel Prize for Planetary Exploration, you would be #1 on the list !

Who is speaking during the EDL commentary? Early through there is one american-sounding guy, then later most of the announcements are by a french-sounding guy. What are their names?

The 'French-sounding' guy actually sounded more Middle Eastern to me (I'm an American, BTW)...but, I have no idea at all.

Google is your friend.

""Phoenix has landed! Phoenix has landed! Welcome to the northern plains of Mars!" mission commentator Richard Kornfeld exclaimed from the control center at the Jet Propulsion Laboratory. "

MahFL is right, it was Richard Kornfeld (good guess - he comes from Switzerland originally). Richard was the lead engineer for orchestrating the "EDL Comm" for Phoenix. He sweated the all of the interfaces and details with Mars Express, Odyssey, MRO, Greenbank and the DSN. Had Phoenix has a failure during EDL, the data being sent and recorded from 3 different spacecraft as well as Earth would have allowed us to figure out what happened and why. Fortunately we did not have to. He did a great job! He is now spending a lot of time bopping over to Tucson to help in surface ops. He really loves Mars time! (not really ... no one does!)

The other voice is Robert Shotwell. Robert was the Phoenix "Project System Engineer" responsible for many things but most importantly he organized and ensured that the verification and validation program for Phoenix was comprehensive and complete. It is an exhaustingly detailed and technically impossible job. But he was outstanding at it.

Real people with real jobs. Each person bringing unique skills and personalities (there was no shortage of personalities on Phoenix). Amazing.

take care,

Rob M.

Richard was such a great narrator. Count me as one vote to have him call out MSL when the time comes, even if he's not part of that team. There's a certain amount of excitement in his voice, but its subtle enough to not be a distraction. That 9 minutes was one of the most exciting and enjoyable as any space related live event in my 47 years of following these events.

EDIT: admittedly I guess I didn't follow my first one too closely, Explorer 11 -- being an infant at the time.

Of course Rob Manning wouldn't be allowed to do that, but I don't see a problem with an anonymous UMSF member going by the user name MarsEngineer, whoever he would be, posting little tidbits from time to time...

I gotta chime in & totally agree with this statement, Dan...it was really terrific, will never forget it!

Of course, one might wonder why JPL, which as far as I know has a team of several people to do nothing but "visualization", would need to do that in the first place.

Geez, Mike, can't you let a guy throw a bone to his fans?

--Emily

Maybe kwan will get a job offer from Maas Digital soon?

Come on Mike - that's not exactly fair. Sometimes, even though the talent is there, the time or money to do something isn't. Surely you more than most here, should understand that.

DOug

Correct me if I'm wrong, but did the lander legs deploy twice in the animation? The first time just after heatshield separation at 4:12? The second time at 5:36.

Well I think in "kwan vs JPL Visualization" (sorry for putting it that way) we are talking about two different things.

Kwan's animation is amazing because it is scientifically and engineering-wise "correct", which is of great excitement for those interested in the science and engineering of it all (i.e. the majority on this forum).

The JPL Visualization's task, I can imagine, is to sell "space" and "spaceflight" to the masses (and hence guarantee funding etc). So that stuff has to look good. I somehow doubt that the big masses do get any excitement out of the big wobbles prior to parachute deploy, the resonances of leg deploy, the steadiness at constant velocity

It would be neat if JPL could build a piece of SW in the lines of Meastro that let us do al kinds of imaging stuff. Give us a course we have to complete. Ensure the program documents all steps the user takes to alter the image, panorama or anaglyph. Unfortunately NASA would need another way to protect it's data. Now their researchers can just keep the calibration data to ensure they can work towards the results they have already invested years in. I guess it would not be very doable to let us all sign an NDA kind of document. It would be cool if we enthusiasts could all help with the 'simple' tasks (as far as simple tasks exist...let me rephrase that to relatively simple, repetitive tasks) to lighten the burden on the team but giving them al the credit were it is due (of course UMSF would be noticed in the image credits ).

Just daydreaming

In my animation, the legs deploy at 4:12-4:13 and stay down. The geometry is poor and most of the event is hidden by the backshell. However, the commentary doesn't mention the legs until 5:35. Either the telemetry for the legs took that long to come down (possible and understandable, mechanical one-time telemetry might run at a slow rate) or the commentator didn't notice until then (Also understandable, he seemed to be focused on the radar telemetry)

As for competing with JPL, nothing I have done is hard. It's about 250 lines of animation script, which is basically just read the table, orient the model, draw the frame, repeated 13152 times. I'd be precisely nowhere without the hard work of the guys at JPL who figured out the stuff that's in the tables (Not to mention getting a real spacecraft to Mars in the first place).

I'm also nowhere near Dan Maas and crew. I make animations to see what things "really look like" and I've been disappointed with a lot of my work because to be honest, space events are hard to film. The lighting is never right. It's hard to see critical events. Space is slow. As mentioned above, two minutes hanging on a parachute? From a fixed view point? Whoopee. Maas and crew, and the vis guys at JPL have the cinematography skills and tools to make these events look good and exciting. I am still practicing. I aspire to Maas-like quality, but I'm still a little ways away.

What I found particularly interesting in this animation was seeing the dynamic instability growing in the aeroshell's angle-of-attack just before parachute deployment. This phenomena was first seen with the Viking aeroshells and would have caused the aeroshells to tumble if Viking didn't have a reaction control system. The dynamic instability is triggered by shockwave separation due to reducing Mach Number but driven by vortices in the aeroshell's wake and real gas effects (very difficult to model).

THAT is an interesting tidbit! So parachute deployment is as much about keeping the vehicle stable at low Mach as it is about deceleration...great dual-application solution.

Has anyone ever considered using a ribbon chute for stabilization & holding off on a main conventional chute for later? Seems like getting a single chute to work properly in supersonic conditions is a real challenge ("squidding"), don't know if its behavior is easier to simulate or predict at lower speeds, nor if it would provide enough deceleration if deployment were deferred.

Yes, the 70 deg. sphere-cone becomes dynamically unstable at around Mach = 1.8 . A 45 deg. sphere-cone such as used with Pioneer Venus or the Galileo Probe can be aerodynamically stable all the way to the ground provided the center-of-gravity is correctly located. However a 45 deg. sphere-cone has significantly less drag that the 70 deg. sphere-cone. Because the Martian atmosphere is so thin, you want the vehicle to decelerate as rapidly as possible (maximum bluntness is highly desireable).



Mars landers use a disk-gap-band parachute because that type parachute can safely deploy at supersonic speed. One would prefer to deploy the parachute subsonically but that's not really an option on Mars due to the thin atmosphere.

Designing parachutes is a black art. Correctly simulating a parachute with a computer model is hard to do. Also squidding can happen at subsonic speeds. The early MER parachute prototypes squidded in the NASA Ames 40 x 80 wind tunnel at subsonic speeds.

No, they also do the visualization of actual data that comes down. See for example the MER airbag bounce movie.