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InSight Cruise Phase, Events during Mars transit prior to EDL
Guest_mcmcmc_*
post Nov 19 2018, 10:25 AM
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QUOTE (mcaplinger @ Nov 18 2018, 11:55 PM) *
I said most of the kernels on the NAIF site don't model the landing. The one I extracted the data from does at least at some level, otherwise I wouldn't have bothered with it.

Download is not working for me neither.
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Guest_mcmcmc_*
post Nov 19 2018, 03:21 PM
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QUOTE (mcaplinger @ Nov 18 2018, 09:06 PM) *
(for example, powered descent duration can't vary by much because you run out of fuel if it goes too long and you crash if it goes too short

this remembers me of something...

how do Phoenix and Insight prevent Schiaparelli final event from happening?
And by the way, recorded data on Phoenix show and incredibly wrong modelization of Pitch, Roll and Yaw for Phoenix:
https://ntrs.nasa.gov/archive/nasa/casi.ntr...20080034645.pdf

(fig. 6, 7, 8).

By the way, is anything similar to Phoenix raw data available for unfortunate Schiaparelli mission? Or was it supposed to upload them once landed?
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mcaplinger
post Nov 19 2018, 03:48 PM
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QUOTE (mcmcmc @ Nov 19 2018, 07:21 AM) *
And by the way, recorded data on Phoenix show and incredibly wrong modelization of Pitch, Roll and Yaw for Phoenix:
By the way, is anything similar to Phoenix raw data available for unfortunate Schiaparelli mission? Or was it supposed to upload them once landed?

Has it occurred to you that maybe the problem is your interpretation of the data, not that they are "incredibly wrong"?

There was some realtime downlink of Schiaparelli data, I think it's described in the failure report. I'd be very surprised if it was online in raw form.

Here's the Insight dump with 1-second intervals.

Attached File  edl.zip ( 2.37MB ) Number of downloads: 203


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Disclaimer: This post is based on public information only. Any opinions are my own.
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Guest_mcmcmc_*
post Nov 19 2018, 09:17 PM
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QUOTE (mcaplinger @ Nov 19 2018, 04:48 PM) *
Has it occurred to you that maybe the problem is your interpretation of the data, not that they are "incredibly wrong"?

Suggestions?
I just see two heavily different curves named "predicted" amd "reconstructed".

QUOTE (mcaplinger @ Nov 19 2018, 04:48 PM) *
Here's the Insight dump with 1-second intervals.

Attached File  edl.zip ( 2.37MB ) Number of downloads: 203


No way to download this file, still gives an error, anyway never mind, I tried setting up the simulator with data I have:
http://win98.altervista.org/space/explorat...-simulator.html

It has yet to be cleaned up and I'll try to also add some fancy graphical instrument like I did here, if I have time, but time is short, only one week remains.
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propguy
post Nov 20 2018, 12:38 AM
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Latest status. We did TCM5 yesterday (could not mention until official announcement came out Official InSight Twitter Page). So far looks like very good maneuver (well than 1 sigma error) and just waiting for Nav results to see if we are setup for entry as expected. Hoping to skip TCM6 this weekend, but ready if we have to do it. Things looking good for EDL.

On a side note, I have been trying to come up with a good EDL song to play that day on the way into work. For launches there are lots of ones that work, but none that seem to cover landing. Best I could think of was Helter Skelter "Coming down fast from miles above you". Good line but the rest of the song does not fit my hopes for that day. Any good ideas?
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nprev
post Nov 20 2018, 02:39 AM
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Thanks for the insight (rimshot!) as always, Propguy. smile.gif

EDL songs...hmm...Rock Lobster? (down, down, down!) biggrin.gif


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mcaplinger
post Nov 20 2018, 04:16 AM
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QUOTE (propguy @ Nov 19 2018, 04:38 PM) *
Any good ideas?

"Eight Miles High" by the Byrds?


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RoverDriver
post Nov 20 2018, 07:08 AM
Post #53


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Going Down, Jeff Beck

"Well I'm going down
Down, down, down, down, down
I'm going down
Down, down, down, down, down
I've got my head out the window
And my big feet on the ground"

It's even 7 minutes long. And play it LOUD!!!

Paolo


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akuo
post Nov 20 2018, 07:55 AM
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The Rasmus - F-F-F-Falling

"I need a flame, I need a spark
Don't be afraid to open my heart
I need a game, I need a shock
Don't be afraid my heart is unlocked
Made up my mind 'bout the music
Made up my mind 'bout the style
I know that I'm stable and able
To settle down
F-f-falling"


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Antti Kuosmanen
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Guest_mcmcmc_*
post Nov 20 2018, 10:02 AM
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QUOTE (propguy @ Nov 20 2018, 01:38 AM) *
Latest status. We did TCM5 yesterday

Good to hear that.
I just found out a weird thing I did not know: during travel toward Mars, probes are not oriented as we see in all videos, but in such a way that solar panels are correctly oriented toward sun, then the "tip turn" (which I would call "Entry Attitude Setup Maneuver") is performed.
I also read that only a short time before Phoenix arrival at atmosphere interface somebody thought that there was a possibility of recontact between cruise stage (or parts of it) and lander after lander deployment, as they're both on same ballistic trajectory, and cruise module is only slightly slowed down by the pyro devices during lander deployment: it was calculated a minimum distance of 6 meters between lander and cruise module during EDL!
So, if I understand correctly, now the lander deployment is performed before EASM, so cruise module is not just slowed down by lander deployment, but it is also put on a different trajectory due to the transverse force impressed by pyro devices; is this interpretation correct?
But if this "Cruise Module Avoidance Maneuver" was introduced only with Phoenix... how did it go for Pathfinder and MERs?
And I wonder if cruise stage falling parts could have messed up Schiaparelli descent.

During Phoenix EDL they also figured out through simulation that thrusters in the backshell can't be used as designed (i.e. during hypersonic phase), because simulations showed that due to "werid" aerodynamic effects and interactions at high speed they could result in a force being applied to the lander in the OPPOSITE direction w.r.t. what the thrusters were supposed to do! So they were not used at all during descent, unless an "emergency situation" was encountered.

These are all interesting manuevers and "rocket science things" which I've never seen in any video, but they would look much more interesting in a video than in a PDF!
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Guest_mcmcmc_*
post Nov 20 2018, 10:08 AM
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QUOTE (mcaplinger @ Nov 19 2018, 04:48 PM) *
There was some realtime downlink of Schiaparelli data, I think it's described in the failure report. I'd be very surprised if it was online in raw form.

I found this PDF which led me to this page which I will have to investigate a lot!


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Guest_mcmcmc_*
post Nov 20 2018, 02:18 PM
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Found another interesting page, which makes more simple to use SPICE (I don't know anything about SPICE but I was able to gather some data):
https://wgc.jpl.nasa.gov:8443/webgeocalc/#StateVector

Unfortunately I can't find data for Insight and Phoenix.
Phoenix is "-84" and Insight is "-189".
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propguy
post Nov 20 2018, 07:53 PM
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QUOTE (mcmcmc @ Nov 20 2018, 03:02 AM) *
Good to hear that.
I just found out a weird thing I did not know: during travel toward Mars, probes are not oriented as we see in all videos, but in such a way that solar panels are correctly oriented toward sun, then the "tip turn" (which I would call "Entry Attitude Setup Maneuver") is performed.
I also read that only a short time before Phoenix arrival at atmosphere interface somebody thought that there was a possibility of recontact between cruise stage (or parts of it) and lander after lander deployment, as they're both on same ballistic trajectory, and cruise module is only slightly slowed down by the pyro devices during lander deployment: it was calculated a minimum distance of 6 meters between lander and cruise module during EDL!
So, if I understand correctly, now the lander deployment is performed before EASM, so cruise module is not just slowed down by lander deployment, but it is also put on a different trajectory due to the transverse force impressed by pyro devices; is this interpretation correct?
But if this "Cruise Module Avoidance Maneuver" was introduced only with Phoenix... how did it go for Pathfinder and MERs?
And I wonder if cruise stage falling parts could have messed up Schiaparelli descent.

During Phoenix EDL they also figured out through simulation that thrusters in the backshell can't be used as designed (i.e. during hypersonic phase), because simulations showed that due to "werid" aerodynamic effects and interactions at high speed they could result in a force being applied to the lander in the OPPOSITE direction w.r.t. what the thrusters were supposed to do! So they were not used at all during descent, unless an "emergency situation" was encountered.

These are all interesting maneuvers and "rocket science things" which I've never seen in any video, but they would look much more interesting in a video than in a PDF!


We do jettison the cruise stage prior to the slew to entry attitude (what you call EASM). That event occurs roughly 30 seconds before the slew begins, which is about 6-7 minutes prior to the start of entry. I am not allowed by ITAR to discuss the why or how come we decided to do that (sorry). I can say that all the EDL monte carlo sims also look for cruise stage contract and flag those runs, so it is not something we have missed or have forgotten. From the limited info I know about the Schiaparelli failure this is an unrelated topic (the publicly available report EXOMARS 2016 - Schiaparelli Anomaly Inquiry shows their failure was due to high rates on the parachute swamping some fault protection values for rates and thus the IMU data was ignored and they miss estimated altitude and shut off the descent engines too early). I doubt any rate that could come from contact with the cruise stage prior to entry could result in rates that created an issue at parachute deployment while still allowing for a successful entry portion (where angles of attack are very narrow for survival).

Regarding the roll reversal issue on the RCS thruster in hypersonic. That was a predict on Phoenix that came out of some a CFD analysis (see page 12 of this paper Analysis of effectiveness of phoenix entry reaction ... - NTRS - NASA). No one is sure if that is accurate or not, but to be safe Phoenix (and InSight) inhibit thruster usage after a certain time in the entry portion to avoid any potential issue. The only thing the RCS would be doing a that time anyway is roll control and as opposed to MSL we do not have a tight roll control requirement on entry (just don't spin up like a top).
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Guest_mcmcmc_*
post Nov 20 2018, 10:07 PM
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QUOTE (propguy @ Nov 20 2018, 08:53 PM) *
From the limited info I know about the Schiaparelli failure this is an unrelated topic (the publicly available report EXOMARS 2016 - Schiaparelli Anomaly Inquiry shows their failure was due to high rates on the parachute swamping some fault protection values[...]

I imagine debris from cruise stage falling over the open parachute amd causing a mess.

Anyway, in the meantime I slightly updated my simulator, now you can see something moving eventually! :-)

http://win98.altervista.org/space/explorat...-simulator.html
Unfortunately data at low altitude are quite low in precision.

It's a pity I have no time to further study and process telemetry data to get a yaw/pitch/roll graphical representation, maybe I'll do on real Insight data once available; for now I can try adding acceleration, and possibly atmosphere data (temp, pressure and density), all contained in same PHXPROFILES.TAB file.
I also see "attack angle" in PHXPROFILES.TAB, I wonder if I can turn it into an image of Phoenix/Insight rotating while going down in these remaining 4 days.
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djellison
post Nov 20 2018, 10:41 PM
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QUOTE (mcmcmc @ Nov 20 2018, 02:07 PM) *
I imagine debris from cruise stage falling over the open parachute amd causing a mess.


Not a statistically likely event. For InSight, the cruise stage separates before the turn to entry - it's not directly following InSight into the atmosphere.

QUOTE
Anyway, in the meantime I slightly updated my simulator, now you can see something moving eventually! :-)

http://win98.altervista.org/space/explorat...-simulator.html


Both the image and the URL are missing...

The requested URL /space/exploration/insight/screenshot1.png was not found on this server.

The requested URL /space/exploration/insight/insight-edl-simulator.html was not found on this server.
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