Author Topic: SpaceX: General Falcon and Dragon discussion (Thread 2) (Read 626207 times)

Art LeBrun · « **Reply #1000 on:** 01/16/2011 03:41 pm »

Quote from: douglas100 on 01/08/2011 09:01 pm

I remember Delta launches from Cape Canaveral of Tiros satellites going to sun-synchronous orbits in the mid 60's. But I think these went on a southerly azimuth and overflew the isthmus of Panama. Whether that would be allowed now I have no idea.

Proposed trajectories for Delta about 1965. I do not know if any of these were flown.

douglas100 · « **Reply #1001 on:** 01/16/2011 06:38 pm »

Thanks for the map.

According to

http://nssdc.gsfc.nasa.gov/nmc/masterCatalog.do?sc=1965-004A

and

http://www.n2yo.com/satellite/?s=978

it seems that Tiros 9 was indeed launched into a retrograde orbit from Cape Canaveral, dog legging on to an azimuth which overflew Cuba then Panama. Can you imagine that being allowed today?

Jim · « **Reply #1002 on:** 01/16/2011 07:37 pm »

Quote from: douglas100 on 01/16/2011 06:38 pm

Thanks for the map.

According to

http://nssdc.gsfc.nasa.gov/nmc/masterCatalog.do?sc=1965-004A

and

http://www.n2yo.com/satellite/?s=978

it seems that Tiros 9 was indeed launched into a retrograde orbit from Cape Canaveral, dog legging on to an azimuth which overflew Cuba then Panama. Can you imagine that being allowed today?

It was a 3 stage Delta and I believe most of the impulse of the 3rd stage was for plane change.

ugordan · « **Reply #1003 on:** 01/17/2011 04:34 pm »

CCDev2 video is back: http://www.spacex.com/multimedia/videos.php?id=58

Robotbeat · « **Reply #1004 on:** 01/17/2011 04:52 pm »

Quote from: ugordan on 01/17/2011 04:34 pm

CCDev2 video is back: http://www.spacex.com/multimedia/videos.php?id=58

BTW, there's a weird bug where the two audio channels when the speaker (Shotwell and Elon) in the corner are talking 180 degrees out of phase with each other, so when combined into a single channel (like for my laptop speaker), you can only hear some artifacts. It's easy to fix this by just adjusting the balance between left and right speakers to be slightly more for the left or right speakers (i.e. not centered) with "Volume Control" in Windows XP.

ugordan · « **Reply #1005 on:** 01/17/2011 04:55 pm »

Yeah, that goes back to the post-flight conference mic problem. One NASA youtube channel does have better audio (still inverted I think), but looks like SpaceX didn't use it.

corrodedNut · « **Reply #1006 on:** 01/17/2011 05:18 pm »

And now there's a new update, relating to their CCDev2 proposal:

http://www.spacex.com/updates.php

docmordrid · « **Reply #1007 on:** 01/17/2011 07:10 pm »

Comparing the thruster shown in the video with a Draco they look different. There appears to be different proportions plus an apparently wider throat. Could this be our first look at the LAS thruster?

ugordan · « **Reply #1008 on:** 01/17/2011 07:15 pm »

It's Merlin 1a.

Rhyshaelkan · « **Reply #1009 on:** 01/17/2011 07:16 pm »

Ick, if as Elon mentioned and the Dragon pulled 4-4.5 Gs. How much will the LAS pull? Granted they are automatic systems I am sure and a few seconds of blackout(or would that be red-out lying on your back that way?) will not be the end of the world

douglas100 · « **Reply #1010 on:** 01/17/2011 07:23 pm »

I guess that if an abort were called at a high G part of the ascent, a shut down command would be sent to the main engine(s) before the LAS was triggered.

baldusi · « **Reply #1011 on:** 01/17/2011 07:27 pm »

Quote from: Rhyshaelkan on 01/17/2011 07:16 pm

Ick, if as Elon mentioned and the Dragon pulled 4-4.5 Gs. How much will the LAS pull? Granted they are automatic systems I am sure and a few seconds of blackout(or would that be red-out lying on your back that way?) will not be the end of the world

It's important to note that in eyeball in, 17G should be tolerable without blackout for a couple of minutes. If you need just a few seconds to clear the area, that should (hopefully) be enough. Specially with the resistance of Dragon's heat shield in your back. In fact, the worst part might be reentry, since you'd be eyeballs out.

ugordan · « **Reply #1012 on:** 01/17/2011 07:29 pm »

Reentry would also be eyeballs-in. Deorbit would be eyeballs-out, but Draco thrust levels are so low this is a non-issue.

baldusi · « **Reply #1013 on:** 01/17/2011 07:40 pm »

Quote from: ugordan on 01/17/2011 07:29 pm

Reentry would also be eyeballs-in. Deorbit would be eyeballs-out, but Draco thrust levels are so low this is a non-issue.

Because the deceleration vector is negative to the advance direction, right?

docmordrid · « **Reply #1014 on:** 01/17/2011 07:42 pm »

OK M1a - then here's another imagery question: why 2 sets of shock cones per quadrant? 8 LAS motors?

ugordan · « **Reply #1015 on:** 01/17/2011 07:48 pm »

Quote from: baldusi on 01/17/2011 07:40 pm

Quote from: ugordan on 01/17/2011 07:29 pm
Reentry would also be eyeballs-in. Deorbit would be eyeballs-out, but Draco thrust levels are so low this is a non-issue.
Because the deceleration vector is negative to the advance direction, right?

Uh, my brain is too slow today to parse that sentence. AIUI, the deorbit burn would be done by the upward-pointing Dracos as the cosine losses for them are lower than the downward-pointing ones, due to the wall angle. So they'd be more efficient.

But at ~6 minutes deorbit burn you're hardly going to notice it anyway.

ugordan · « **Reply #1016 on:** 01/17/2011 07:49 pm »

Quote from: docmordrid on 01/17/2011 07:42 pm

why 2 sets of shock cones per quadrant? 8 LAS motors?

Thrust level limits or redundancy considerations?

Crispy · « **Reply #1017 on:** 01/17/2011 07:50 pm »

Quote from: docmordrid on 01/17/2011 07:42 pm

OK M1a - then here's another imagery question: why 2 sets of shock cones per quadrant? 8 LAS motors?

Redundancy, surely

kraisee · « **Reply #1018 on:** 01/17/2011 07:58 pm »

Quote from: douglas100 on 01/17/2011 07:23 pm

I guess that if an abort were called at a high G part of the ascent, a shut down command would be sent to the main engine(s) before the LAS was triggered.

Yes, but in emergencies, there are never any guarantees that command will actually shut it down successfully.

Thus, your LAS design has to assume a failure to shut down the booster is one of the multitude of conditions it must cope with.

Abort systems are some of the hardest design challenges, because they have to start-out assuming most of the worst possible case scenario's have already occurred.

Ross.

baldusi · « **Reply #1019 on:** 01/17/2011 08:03 pm »

Quote from: kraisee on 01/17/2011 07:58 pm

Thus, your LAS design has to assume a failure to shut down the booster is one of the multitude of conditions it must cope with.

Shouldn't the worst acceleration condition be a case of engine overdrive? Is it even possible that a failure in one engine generates a significant extra thrust? Would this be worse (from an acceleration POV) than a catastrophic failure like Challenger?