IPB

Welcome Guest ( Log In | Register )

13 Pages V  < 1 2 3 4 > »   
Closed TopicStart new topic
MSL Cruise Phase
Explorer1
post Nov 27 2011, 12:01 AM
Post #16


Senior Member
****

Group: Members
Posts: 2073
Joined: 13-February 10
From: Ontario
Member No.: 5221



Actually the last EDL was in 2008 with the Phoenix; though that wasn't a rover though right? wink.gif
Go to the top of the page
 
+Quote Post
Guest_Oersted_*
post Nov 27 2011, 12:20 AM
Post #17





Guests






QUOTE (MarsEngineer @ Nov 26 2011, 10:51 PM) *
Did you enjoy that launch as much as I did? It is very surreal to see stuff that you have had your hands on being pushed up and up into the sky like that, knowing it is not likely to return to Earth any time soon.


I sat in my apartment in Brussels, Belgium, rooting animatedly for MSL and eating too many peanuts while my pregnant wife Sandra watched TV, slightly bemused. Our girl will be born in late March next year, if all goes well, and I am hoping that she and MSL will share parallel journeys of discovery on neighbouring planets in this solar system of ours.

I cannot imagine a better example of what's best about humanity to show to her, through her childhood and hopefully adolescence. Science, cooperation, a quest for knowledge: All these good traits that can be summed up in one word, Curiosity, are what I want to hold up to my daughter as an example of what to strive for.

So, yes, you can say that emotionally I have a lot riding on Curiosity.

I feel privileged to be vicariously part of the ride and now look forward to a quiet and relaxing cruise stage while I, personally, reach other deadlines here on Earth... smile.gif
Go to the top of the page
 
+Quote Post
Guest_Oersted_*
post Nov 27 2011, 12:44 AM
Post #18





Guests






I uploaded footage of the launch and spacecraft separation for those who might not have been able to see it...

http://www.youtube.com/user/wwwDOTdalsgaar...4/0/qOJqDNp2afE

http://www.youtube.com/user/wwwDOTdalsgaar...4/1/k9xpePuiqA8
Go to the top of the page
 
+Quote Post
Syrinx
post Nov 27 2011, 02:02 AM
Post #19


Member
***

Group: Members
Posts: 131
Joined: 31-May 08
From: San Carlos, California, USA
Member No.: 4168



Thank you sir for the videos. I was unable to watch this morning due to my Texas -> California launch on a Boeing first stage.
Go to the top of the page
 
+Quote Post
tanjent
post Nov 27 2011, 03:34 AM
Post #20


Member
***

Group: Members
Posts: 214
Joined: 30-December 05
Member No.: 628



I'm having some trouble with "data dropouts" myself while trying to view the videos - I wanted to review the telemetry data on the evolution of perigee and apogee during the second Centaur burn, because the first time through I did not understand what I was seeing. My recollection is that after a steady increase the apogee figures dropped abruptly somewhere over Madagascar. This may have simply indicated a move to a higher power of 10 on the display but it was too blurry to be sure. The perigee seemed to be stuck somewhere in the 80's or -80's (couldn't tell if it was a negative sign or a "star" in the simulation). This I really did not understand because it persisted even after the spacecraft was well on its way to Mars. Is it just that after a certain point the perigee ceased to update? Maybe some rocket scientist here can explain how the perigee figure would be expected to evolve if we actually continued to track it as the spacecraft approaches escape velocity. Seems to me both apogee and perigee would eventually have to go to infinity at the point where the vehicle transitions to a solar orbit but when it becomes possible to view the video without a "please try again later" message I am sure it will confirm that this is not what we actually saw.
Go to the top of the page
 
+Quote Post
john_s
post Nov 27 2011, 03:54 AM
Post #21


Member
***

Group: Members
Posts: 696
Joined: 3-December 04
From: Boulder, Colorado, USA
Member No.: 117



I was watching those numbers too. The apogee should have gone infinite when MSL reached escape speed- if I recall correctly it actually went negative on the display, though the moment of reaching escape was missed in the NASA feed because of a cutaway to the launch control center. Perigee however should stay finite- after engine cutoff the the spacecraft was on a hyperbolic trajectory relative to the earth, and a hyperbola has a well-defined closest approach point to Earth (perigee). The actual value of perigee could go up or down during the burn depending on the burn direction- theoretically I suppose it could end up below the Earth's surface, though it would probably not be fuel-efficient to bend the trajectory in that direction.

John
Go to the top of the page
 
+Quote Post
tanjent
post Nov 27 2011, 04:04 AM
Post #22


Member
***

Group: Members
Posts: 214
Joined: 30-December 05
Member No.: 628



OK - I bet it actually finds the perigee by looking backwards along its escape hyperbola, and naturally that would intersect the earth at some point. Got it, I think!
Go to the top of the page
 
+Quote Post
MahFL
post Nov 27 2011, 04:49 AM
Post #23


Forum Contributor
****

Group: Members
Posts: 1372
Joined: 8-February 04
From: North East Florida, USA.
Member No.: 11



The separation video was just awesome, although I did not know the back side of the cruise stage was covered with solar panels, so I was a bit unsure of what exactly I was looking at, but it looked fantastic.
Go to the top of the page
 
+Quote Post
OKB001
post Nov 27 2011, 05:59 AM
Post #24


Junior Member
**

Group: Members
Posts: 21
Joined: 15-December 08
Member No.: 4509



QUOTE (MahFL @ Nov 26 2011, 08:49 PM) *
The separation video was just awesome, although I did not know the back side of the cruise stage was covered with solar panels, so I was a bit unsure of what exactly I was looking at, but it looked fantastic.


It sure did. Although, I was hoping for a bit more live feed from the onboard cameras during the flight ... oh well.
Go to the top of the page
 
+Quote Post
kwan3217
post Nov 27 2011, 02:23 PM
Post #25


Junior Member
**

Group: Members
Posts: 89
Joined: 27-August 05
From: Eccentric Mars orbit
Member No.: 477



(Full inline quote removed- Mod)

The apogee for a perfect parabola is infinite, but if you run the formulas to find the perigee and apogee of an ellipse, on a hyperbola, you will get the correct perigee but a finite, negative apogee. Obviously a distance can never be negative (you can never be closer to me than at my same position, with zero distance) but you can run all the formulas in reverse with this negative apogee and get the correct position and velocity of the spacecraft.

Which brings me to my second point: There is in theory enough information in the elements to get the position and velocity of the spacecraft during the burns, if they are all consistent. One thing I don't know is how they handle "altitude". A really common way to do it is to take the radius distance from the center and subtract the equatorial radius of the Earth, but since the Earth is not a perfect sphere, this would result in a negative altitude at launch. So I don't know what you have to add to get back the radius vector, and it may be two different things for different altitudes. I remember seeing one of these simulations where the altitude wasn't in between periapse and apoapse.

Back to the original point: Since the apogee took one value and stuck with it after escape velocity was achieved, maybe they just put in some fill value, like -9999999 meters, and translated it to nautical miles. In which case, after escape, the orbital elements become insufficient to reconstruct position and velocity.
Go to the top of the page
 
+Quote Post
tanjent
post Nov 27 2011, 02:50 PM
Post #26


Member
***

Group: Members
Posts: 214
Joined: 30-December 05
Member No.: 628



Well, the altitude should be directly observable by the spacecraft avionics with no mathematical projection required. But you may be right, Kwan, because, as you mentioned, there were periods during the second burn when it seemed to be decreasing. I took this to mean that we were accelerating towards the Mars transfer orbit along a path that initially was sub-tangential to the curvature of the earth. Really, I wish I could see the telemetry readout again without having to watch those tiny blurry numbers in the corner of the simulation video. Dmuller should write them a little package that could run independently in its own window!
Go to the top of the page
 
+Quote Post
scalbers
post Nov 27 2011, 04:08 PM
Post #27


Senior Member
****

Group: Members
Posts: 1622
Joined: 5-March 05
From: Boulder, CO
Member No.: 184



QUOTE (kwan3217 @ Nov 27 2011, 03:23 PM) *
Back to the original point: Since the apogee took one value and stuck with it after escape velocity was achieved, maybe they just put in some fill value, like -9999999 meters, and translated it to nautical miles. In which case, after escape, the orbital elements become insufficient to reconstruct position and velocity.

Yes those numbers were fascinating. I assumed we just had one look at the numbers after the orbit went hyperbolic (eccentricity > 1). It seemed a reasonable value of negative apogee for a hyperbolic orbit. Osculating orbital elements of course can always be converted to an instantaneous position and velocity. I wrote a FORTRAN subroutine a long time ago that does this conversion - at least for heliocentric orbits.

I wonder what the earth-relative velocity and eccentricity values were when the engines cut off? It takes about 3.2 km/sec delta-V to go from low-Earth orbit to reach escape velocity (11.3 km/sec). Another 0.6 km/sec or so is needed to get to a Mars transfer orbit, though it looks from this press-kit excerpt that the actual excess velocity is more like 3.3 km/sec.

Orbit at SC Separation
Perigee: 104.0 km
Inclination: 35.5 deg
Hyperbolic Departure
Hyperbolic Excess Velocity Squared (C3): 10.78 km2/sec2
Declination of the Launch Asymtote (DLA): -1.10 deg
Right Ascention of the Launch Asymtote (RLA): 126.6 deg

Approximate Values
Orbit parameters shown for launch on 25 Nov 2011 at 10:25 a.m. EST.

And the following velocity equation from Wikipedia can help get back the semimajor axis, and then the eccentricity:

http://en.wikipedia.org/wiki/Elliptic_orbit

Steve
Go to the top of the page
 
+Quote Post
Astro0
post Nov 27 2011, 10:05 PM
Post #28


Senior Member
****

Group: Admin
Posts: 3108
Joined: 21-December 05
From: Canberra, Australia
Member No.: 615



A little late to the party I guess. My weekend was very busy with our very first NASA-style Tweetup at the CanberraDSN.
A large group watched the launch on our big screen (at 2.02am!) and then headed out to watch our antennas acquire the spacecraft shortly after its separation and the beginning of its cruise to Mars.

A few hours later I headed back out into the light of dawn and snapped this panorama of our dishes at work.

Attached Image


That's DSS34 on the left tracking Curiosity; DSS43 in the middle tracking Mars Odyssey and MRO (warning them that's something is on its way); and just past the rainbow on the right is DSS45, which was the prime antenna for the acquisition and also tracking Curiosity when this photo was taken. Note: it may look as if DSS34 and DSS45 are pointing in opposite directions but wrap that panorama around and they are pointing the same way.
Go to the top of the page
 
+Quote Post
Guest_Oersted_*
post Nov 27 2011, 10:30 PM
Post #29





Guests






Oh, a rainbow to boot! Lovely panorama and thanks for the explanation about the various antennas.
Go to the top of the page
 
+Quote Post
MarsEngineer
post Nov 28 2011, 12:36 AM
Post #30


Junior Member
**

Group: Members
Posts: 89
Joined: 25-January 06
Member No.: 661



QUOTE (Astro0 @ Nov 27 2011, 02:05 PM) *
A little late to the party I guess. My weekend was very busy with our very first NASA-style Tweetup at the CanberraDSN.
A large group watched the launch on our big screen (at 2.02am!) and then headed out to watch our antennas acquire the spacecraft shortly after its separation and the beginning of its cruise to Mars.

A few hours later I headed back out into the light of dawn and snapped this panorama of our dishes at work.

Attached Image


That's DSS34 on the left tracking Curiosity; DSS43 in the middle tracking Mars Odyssey and MRO (warning them that's something is on its way); and just past the rainbow on the right is DSS45, which was the prime antenna for the acquisition and also tracking Curiosity when this photo was taken. Note: it may look as if DSS34 and DSS45 are pointing in opposite directions but wrap that panorama around and they are pointing the same way.


Hi Astro0,

Would you mind if I shared this with the MSL gang here at JPL? They would LOVE it! (I did) Who shall I give credit?

-Rob Manning (MSL chief engineer)
Go to the top of the page
 
+Quote Post

13 Pages V  < 1 2 3 4 > » 
Closed TopicStart new topic

 



RSS Lo-Fi Version Time is now: 30th March 2024 - 03:37 AM
RULES AND GUIDELINES
Please read the Forum Rules and Guidelines before posting.

IMAGE COPYRIGHT
Images posted on UnmannedSpaceflight.com may be copyrighted. Do not reproduce without permission. Read here for further information on space images and copyright.

OPINIONS AND MODERATION
Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators.
SUPPORT THE FORUM
Unmannedspaceflight.com is funded by the Planetary Society. Please consider supporting our work and many other projects by donating to the Society or becoming a member.