Author Topic: SpaceX Falcon 9 v1.1 - SES-8 - DISCUSSION THREAD (Read 611282 times)

robertross · « **Reply #140 on:** 10/02/2013 01:25 am »

Quote from: Joffan on 09/30/2013 07:38 pm

In honour of the geostationary orbit, I'll suggest "The Day the Earth Stood Still" for the party thread.

Really like that one.

I would also throw out: "David vs Goliath", in the same spirit of the comment by Antares on going up against the big guys (ULA, ESA, Russia).

Jakusb · « **Reply #141 on:** 10/02/2013 06:55 am »

SpaceEkS does it again....?!

corrodedNut · « **Reply #142 on:** 10/02/2013 11:09 am »

Is this a night launch? How about: "Back in Black"

smoliarm · « **Reply #143 on:** 10/02/2013 12:49 pm »

Quote from: ugordan on 10/01/2013 09:30 pm

...
As per Elon's press conference, the Cassiope burn to depletion was to have been directed sideways, not prograde.

...

So, their plan was to change the orbit plane with the second burn?
If yes, the reason would be to demonstrate [simulate] secondary payload deployment into substantially different orbit, right?

And this press conference - is the recording available somewhere?

neoforce · « **Reply #144 on:** 10/02/2013 01:01 pm »

Quote from: smoliarm on 10/02/2013 12:49 pm

...

And this press conference - is the recording available somewhere?

The recording and a transcript is on L2 right now. I'm sure it will be out in general in the next week or two.

<edit> dumb user errors including having the quote outside of the box, and then double posting.

ugordan · « **Reply #145 on:** 10/02/2013 01:42 pm »

Quote from: smoliarm on 10/02/2013 12:49 pm

So, their plan was to change the orbit plane with the second burn?

It would mostly change the inclination a bit, yes, with a modest perigee or apogee change.

Quote

If yes, the reason would be to demonstrate [simulate] secondary payload deployment into substantially different orbit, right?

I think it's just a way to measure how much propellant is left in the tanks without actually worrying about ending up in a massively uncertain orbit in terms of eccentricity.

yg1968 · « **Reply #146 on:** 10/02/2013 02:21 pm »

Quote

SES: We'll wait for SpaceX details on non-reignition of Falcon 9 upper stage before shipping SES-8. Anyway Cape closed w/ govt shutdown...

https://twitter.com/pbdes/status/385401514409209856

psloss · « **Reply #147 on:** 10/02/2013 02:25 pm »

Quote from: yg1968 on 10/02/2013 02:21 pm

Quote
SES: We'll wait for SpaceX details on non-reignition of Falcon 9 upper stage before shipping SES-8. Anyway Cape closed w/ govt shutdown...
https://twitter.com/pbdes/status/385401514409209856

Thanks for the pointer. Peter B. de Selding writes for SpaceNews.com...probably worth keeping an eye out for a story there.

padrat · « **Reply #148 on:** 10/02/2013 02:59 pm »

Don't always believe the media.

That's all I'm saying.....

(present company excluded, Chris

)

docmordrid · « **Reply #149 on:** 10/02/2013 03:09 pm »

Here is part of de Selding's SES-8 atticle-

http://www.spacenews.com/article/launch-report/37513as-next-customer-on-falcon-9-manifest-ses-awaits-details-on-sept-29

Quote

>
The shutdown of the U.S. government has rendered moot the date of SES-8’s launch from Cape Canaveral Air Force Station, Fla. Feltes said no new launches are moving forward during the shutdown. SES-8’s manufacturer, Orbital Sciences Corp. of Dulles, Va., is weighing whether to send the satellite to Florida aboard a truck once SES has authorized its shipment to the spaceport.

smoliarm · « **Reply #150 on:** 10/02/2013 04:22 pm »

Quote from: ugordan on 10/02/2013 01:42 pm

Quote from: smoliarm on 10/02/2013 12:49 pm
So, their plan was to change the orbit plane with the second burn?

It would mostly change the inclination a bit, yes, with a modest perigee or apogee change.

Quote
If yes, the reason would be to demonstrate [simulate] secondary payload deployment into substantially different orbit, right?

I think it's just a way to measure how much propellant is left in the tanks without actually worrying about ending up in a massively uncertain orbit in terms of eccentricity.

Thanks for clarification

Andy USA · « **Reply #151 on:** 10/03/2013 03:27 am »

Removed the off topic posts.

This is, however, on topic, not that the newbies realize we have a news site here.
SES-8 heads to Florida for next Falcon 9 v1.1 launch
http://www.nasaspaceflight.com/2013/10/ses-8-florida-next-falcon-9-v1-1-launch/

InfraNut2 · « **Reply #152 on:** 10/03/2013 06:49 am »

MODERATORS: I intended to put this post in the CASSIOPE mission discussion thread, but it ended here in the SES-8 discussion thread due to a mix-up. Feel free to move this message and any follow-ups there, if desired. It is, however, somewhat relevant here too.

What is "an extended spin start" ?

EDIT: Is it just unusual wording for the initial (or maybe whole) spin-up of the turbopumps taking longer than expected, or is it a more specific but obscure term? (I assume that the Merlin spin up the turbopumps with helium a bit before igniting the gas generator to spin them up the rest of the way to full speed/power, like some other similar engines).

I have picked up a lots of pieces of rocket science from following good news and forum sites like NSF for many years and some deep-diving into in-depth documents etc, but I have not come across this term until now.

------------

From the new NSF article Andy mentioned:

Quote

“We essentially saw the engine initiate ignition, get up to about 400 psi and then it encountered a condition that it didn’t like. It may have been due to an extended spin start, maybe, but this is speculative. So it initiated an abort of the restart. But we have all of the data.

“Before deciding what the issue was, I think we want a bit more time to read the data, before coming to a conclusion,”

InfraNut2 · « **Reply #153 on:** 10/03/2013 09:32 am »

Quote from: InfraNut2 on 10/03/2013 06:49 am

What is "an extended spin start" ?

EDIT: Is it just unusual wording for the initial (or maybe whole) spin-up of the turbopumps taking longer than expected, or is it a more specific but obscure term? (I assume that the Merlin spin up the turbopumps with helium a bit before igniting the gas generator to spin them up the rest of the way to full speed/power, like some other similar engines).

I have picked up a lots of pieces of rocket science from following good news and forum sites like NSF for many years and some deep-diving into in-depth documents etc, but I have not come across this term until now.

------------

From the new NSF article Andy mentioned:

Quote
“We essentially saw the engine initiate ignition, get up to about 400 psi and then it encountered a condition that it didn’t like. It may have been due to an extended spin start, maybe, but this is speculative. So it initiated an abort of the restart. But we have all of the data.

“Before deciding what the issue was, I think we want a bit more time to read the data, before coming to a conclusion,”

I have found a partial answer myself, at least to the "spin start" part. It indeed refers to the initial spin up of the turbopumps with helium.

Initial search efforts just yielded a few news articles with mentions of the term related to Merlin and RS-68 without explanation, but some improved search-fu led me back to this forum (of course

) and this informative post (related to the check-valve issue in the hotfire of an earlier F9):

http://forum.nasaspaceflight.com/index.php?topic=20799.msg559173#msg559173

EDIT: fixed minor typo/formatting glitches

Hooperball · « **Reply #154 on:** 10/03/2013 12:21 pm »

"it encountered a condition that it didn’t like. It may have been due to an extended spin start"

"Extended spin start" is probably a automatic shutdown where the turbo pump didn't achieve a minimum RPM within a set period of time. I'm surprised they used chamber pressure or pump outlet pressure to determine this rather than pump RPM.

S

Jim · « **Reply #155 on:** 10/03/2013 12:26 pm »

Quote from: Hooperball on 10/03/2013 12:21 pm

"it encountered a condition that it didn’t like. It may have been due to an extended spin start"

"Extended spin start" is probably a automatic shutdown where the turbo pump didn't achieve a minimum RPM within a set period of time. I'm surprised they used chamber pressure or pump outlet pressure to determine this rather than pump RPM.

No where does it say they didn't. The likely explanation is a extended spin start occurs when chamber pressure doesn't achieve the correct parameters in the required time.

Hooperball · « **Reply #156 on:** 10/03/2013 01:14 pm »

Quote from: Jim on 10/03/2013 12:26 pm

Quote from: Hooperball on 10/03/2013 12:21 pm
"it encountered a condition that it didn’t like. It may have been due to an extended spin start"

"Extended spin start" is probably a automatic shutdown where the turbo pump didn't achieve a minimum RPM within a set period of time. I'm surprised they used chamber pressure or pump outlet pressure to determine this rather than pump RPM.

No where does it say they didn't. The likely explanation is a extended spin start occurs when chamber pressure doesn't achieve the correct parameters in the required time.

Right... "an extended spin start" might be a mode of failure rather than an auto shut down. And pump discharge pressure caused the auto shut down rather than pump RPM.

If they know pump RPM then they can rule out a leak down stream....

S

Jim · « **Reply #157 on:** 10/03/2013 01:16 pm »

Quote from: Hooperball on 10/03/2013 01:14 pm

Right... "an extended spin start" might be a mode of failure rather than an auto shut down. And pump discharge pressure caused the auto shut down rather than pump RPM.

More likely chamber or GG pressure.

Lar · « **Reply #158 on:** 10/03/2013 04:42 pm »

Wouldn't pump RPM require some sort of tachometer on the shaft? With concomitant weight, reliability, and power consumption (shaft power) issues compared to a pressure sensor? How small and how reliable can you make a tach? I understand tachs are done using magnets bonded to the shaft (extension) and stator loops with current sensors, but I may be confused, so there's no actual physical contact but still...

savuporo · « **Reply #159 on:** 10/03/2013 05:12 pm »

Quote from: Lar on 10/03/2013 04:42 pm

How small and how reliable can you make a tach?

Very, very small. And nobody builds tachs requiring physical contact. Fully optical or magnetic/ hall effect tach is trivial.