Phoenix Final Descent Trajectory Options

[djellison]

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

[Stu]

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...

[jamescanvin]

Did anyone else feel those Landing Night butterflies take wing in their stomachs again when they heard the soundtrack?

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

[MahFL]

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.

[Guest_Oersted_*]

..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!

[dmuller]

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?

[kwan3217]

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.

[nprev]

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

[MarsEngineer]

Version 1B

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.

[dmuller]

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 ...

[vikingmars]

Wow wow Kwan. Very nice job.

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

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 !

[kwan3217]

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?

[nprev]

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

[MahFL]

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?

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. "

[MarsEngineer]

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?

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.