Author Topic: SpaceX Falcon 9 FT - ORBCOMM-2 - Dec. 21, 2015 (Return To Flight) DISCUSSION (Read 1360651 times)

ericspittle · « **Reply #1320 on:** 12/21/2015 09:18 pm »

Quote from: Johnnyhinbos on 12/21/2015 09:09 pm

Quote from: photonic on 12/21/2015 08:30 pm
Quote from: Lars-J on 12/21/2015 08:14 pm
SpaceX tweeted a close-up of the stretched interstage, stretched upper stage, and fairing: https://twitter.com/SpaceX/status/679039057180024832

(note the grid fins now lack a fairing, as we were told by a source earlier)
Is it the lighting, or does the inter-stage really look so dirty? Almost looks like someone painted it over hastily. Just curious, what matters is obviously that it launches and lands in one piece ...

That's been driving me nuts too. It's more than just dirt. It fully looks patched. There has to be a better reason than cryo cooling. Look at the attached pic (credit Jeff Seibert). That area above the SpaceX logo looks like they peeled off duct tape and left a clean spot behind...

Is it possible this is just icing that has and hasn't fallen off?

BrakeFirst · « **Reply #1321 on:** 12/21/2015 09:19 pm »

Wondered about the patches, scuffs and varying paint. Then wondered if they are trying to make new and used look cosmetically about the same.

Likely time and priorities for this particular launch.

Chris Bergin · « **Reply #1322 on:** 12/21/2015 09:20 pm »

The thread has already moved on, but remember we have a standalone thread covering the SpaceX Deep Cryo LOX Discussion.

You should pay it a visit. It's really............err cool!

(Thanks, I'm here all night).

http://forum.nasaspaceflight.com/index.php?topic=39072.0

leetdan · « **Reply #1323 on:** 12/21/2015 09:36 pm »

I'm not sure if this was posted before, but here is the modeled profile of the reentry boom.

Edit: The source is the CCAFS LC-13 Environmental Assessment PDF posted earlier

edkyle99 · « **Reply #1324 on:** 12/21/2015 09:42 pm »

Quote from: BrakeFirst on 12/21/2015 09:19 pm

Wondered about the patches, scuffs and varying paint. Then wondered if they are trying to make new and used look cosmetically about the same.
Likely time and priorities for this particular launch.

This vehicle went through a static firing recently, which could have deposited soot in varying patterns. It also was fired multiple times in Texas.

- Ed Kyle

Joaosg · « **Reply #1325 on:** 12/21/2015 09:43 pm »

Has anyone posted this yet? This is the first picture i saw of the X1 pad.

Was on reddit, and that landing pad looks awesome and huge!

Edit: Found that the original pic is from SpaceX website: http://www.spacex.com/sites/spacex/files/landing_pad_3.2.jpg

(all the credit to reddit spacex irc)

The concrete looks perfect for a landing bingo when we have a drone pic from above

S.Paulissen · « **Reply #1326 on:** 12/21/2015 09:59 pm »

I measure that pad as 302ft wide as long as the person is 6' tall.

Comga · « **Reply #1327 on:** 12/21/2015 10:02 pm »

Quote from: Joaosg on 12/21/2015 09:43 pm

Has anyone posted this yet? This is the first picture i saw of the X1 pad.

Was on reddit, and that landing pad looks awesome and huge!

Edit: Found that the original pic is from SpaceX website: (snip)

(all the credit to reddit spacex irc)

This has now been posted to the Discussion thread, the Updates thread, and the Eastern Range Landing Facilities thread.
Just in case anyone missed it...

llanitedave · « **Reply #1328 on:** 12/21/2015 10:02 pm »

Are those water cannon on the stands just off the pad? I'm wondering about the location of any remote cameras too.

Mapperuo · « **Reply #1329 on:** 12/21/2015 10:09 pm »

Quote from: llanitedave on 12/21/2015 10:02 pm

Are those water cannon on the stands just off the pad? I'm wondering about the location of any remote cameras too.

Just a guess. But the white box middle of photo off the pad could be a camera/comm box.

deltaV · « **Reply #1330 on:** 12/21/2015 10:10 pm »

From the update thread:

Quote from: mrhuggy on 12/21/2015 10:00 pm

Landing Weather Looks good

That image shows a landing wind limit of 50 mph! Wind force scales as the square of velocity so this suggests that landing winds were not the cause of the mysterious 24 hour delay of this launch.

Lars-J · « **Reply #1331 on:** 12/21/2015 10:13 pm »

Quote from: deltaV on 12/21/2015 10:10 pm

From the update thread:
Quote from: mrhuggy on 12/21/2015 10:00 pm
Landing Weather Looks good
That image shows a landing wind limit of 50 mph! Wind force scales as the square of velocity so this suggests that landing winds were not the cause of the mysterious 24 hour delay of this launch.

Yes, but the less wind the better for a first attempt. 50mph might be the limit they think the system should be able to handle, but you would never do a first test of something in the worst conditions you can theoretically handle.

Joaosg · « **Reply #1332 on:** 12/21/2015 10:13 pm »

Quote from: llanitedave on 12/21/2015 10:02 pm

Are those water cannon on the stands just off the pad? I'm wondering about the location of any remote cameras too.

Could be, and probably are. The ASDS had them at the top of the containers. Probably remore operated to quickly extinguish any fire after landing.

Would be cool if the guy in the picture was Elon, but doesn't looks like him.

deltaV · « **Reply #1333 on:** 12/21/2015 10:23 pm »

Quote from: SpaceX Press Kit v2

00:02:35 2nd stage engine starts
00:03 Fairing deployment
00:04 1st stage boostback burn

Any idea why there's a roughly 2 minute delay between second stage engine start and the boostback burn? That'll put them a few hundred km further down-range than if they boosted back immediately. Maybe they have plenty of margin and want to make sure that even if the first stage's control system messes up and points its engines at the second stage, or the stage explodes, the second stage will be safe?

ThereIWas3 · « **Reply #1334 on:** 12/21/2015 10:30 pm »

Maybe that is to allow the 1st stage to do its end-over flip.

AncientU · « **Reply #1335 on:** 12/21/2015 10:31 pm »

Doesn't reaching back to the atmospheric interface perform the fuel settling function? Since the vehicle flips end-to-end after separation, and is above any sensible atmosphere, the small amount of fuel remaining must fully dispersed in the tanks. Hitting the upper atmosphere would begin deceleration and collect the fuel at the plumbing end.

Lars-J · « **Reply #1336 on:** 12/21/2015 10:37 pm »

Quote from: AncientU on 12/21/2015 10:31 pm

Doesn't reaching back to the atmospheric interface perform the fuel settling function? Since the vehicle flips end-to-end after separation, and is above any sensible atmosphere, the small amount of fuel remaining must fully dispersed in the tanks. Hitting the upper atmosphere would begin deceleration and collect the fuel at the plumbing end.

Yes, but at MECO/stage separation, the stage is at an upwards trajectory that will take it to roughly 160 km before falling back and hitting significant atmospheric friction. (~60-70km)? At that point the stage will be MUCH further downrange... So it is important to do the boost-back burn as soon as possible, you can't wait until the atmosphere settles the propellant.

So I think ThereIWas3 is correct... the time is needed to:
1) ensure separation distance between the 1st and 2nd stage
2) flip the stage (using the nitrogen RCS)
3) settle the propellant (using the nitrogen RCS)
...before starting the boost-back burn.

Once that boost-back burn is complete, no more propellant settling is required, since the atmospheric friction will do it.

andrewsdanj · « **Reply #1337 on:** 12/21/2015 10:37 pm »

Looking at the landing limits status window posted over on the update thread. "Landing Winds Below 160 feet (<50 mph)". A 50 mph wind limit? That sounds a bit... 'sporting'.

OxCartMark · « **Reply #1338 on:** 12/21/2015 10:38 pm »

Quote from: deltaV on 12/21/2015 10:23 pm

Quote from: SpaceX Press Kit v2
00:02:35 2nd stage engine starts
00:03 Fairing deployment
00:04 1st stage boostback burn
Any idea why there's a roughly 2 minute delay between second stage engine start and the boostback burn? That'll put them a few hundred km further down-range than if they boosted back immediately. Maybe they have plenty of margin and want to make sure that even if the first stage's control system messes up and points its engines at the second stage, or the stage explodes, the second stage will be safe?

guess: Its a long long piece of equipment being turned by only nitrogen jets, then there might be more time to cancel the rotation and then ullage settling time. The timeline may or may not show 2 minutes since the times are so rounded but I agree its going to go quite a ways downrange during that time and have to get back. In the FH video it happens in (IIRC) ~ 5 seconds.

Quote from: andrewsdanj on 12/21/2015 10:37 pm

Looking at the landing limits status window posted over on the update thread. "Landing Winds Below 160 feet (<50 mph)". A 50 mph wind limit? That sounds a bit... 'sporting'.

Not only sporting to land in but also it would seem to create an interesting problem in remaining standing. Wind load on a 12' diameter x 170(?) foot long cylinder at that wind speed must be tremendous and would seem to risk tipping or skidding. A fun and relatively straightforward calculation for anyone that feels a bit bored.

LouScheffer · « **Reply #1339 on:** 12/21/2015 10:40 pm »

Quote from: BrakeFirst on 12/21/2015 09:19 pm

Wondered about the patches, scuffs and varying paint. Then wondered if they are trying to make new and used look cosmetically about the same.
Likely time and priorities for this particular launch.

Inspired by Star Wars, they are trying for that used rocket look.