Author Topic: SpaceX COTS Demo 1 Updates  (Read 676150 times)

Offline kevin-rf

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Re: SpaceX COTS Demo 1 Updates
« Reply #1320 on: 12/31/2010 12:40 am »
As long as you track the first stage after seperation ;)

Question, I know orbital reentry speeds cause enough ionization to make communications difficult. Is the first stage going fast enough to have similar issues?
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Offline ugordan

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Re: SpaceX COTS Demo 1 Updates
« Reply #1321 on: 12/31/2010 12:44 am »
True, but today we don't need to use film, we have the capability to broadcast, receive, and store HD quality video using tiny devices.

Then you don't have to hope that any magic box survives in order to tell you what went wrong.

Without a high gain antenna tracking the stage which has omi antennas, I don't think you can expect live video. F9 first stage drops below the horizon for ground tracking stations so the only solution would be to equip the Shuttle recovery boats for tracking. Which would cost $.

It's cheaper for SpaceX to try recovery pods first and then try other options if that fails.

Offline kevin-rf

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Re: SpaceX COTS Demo 1 Updates
« Reply #1322 on: 12/31/2010 12:46 am »
Doesn't there also exist a specially equipped P-3 that could also do the tracking job?
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Offline nooneofconsequence

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Re: SpaceX COTS Demo 1 Updates
« Reply #1323 on: 12/31/2010 12:46 am »
Back in the bad old days when we actually had the capability to land men on the moon, telemetry meant that you collected the signals you needed, and downlinked them.  They were then recorded.

I know that we live in a brave new digital world, but everyone wanting to build some super duper flight recorder for the F9 first stage is mucking it up, in my opinion.  Unnecessarily complicated, unnecessarily rugged.

Do the same thing that the OGBs did- perhaps as simple as a couple of rocket cams to watch what happens and a simple transmitter spewing TLM for a ground station to record. 
Telemetry and FDR's serve different primary purposes - telemetry is necessarily condensed, and in the design of what to down link you are constantly trying to balance the needs of sampling rate with sample size and support enough coverage for fault analysis - its an art.

On the other hand, our data driven analysis can suck dry the largest firehoses of data ... and still we want more. Complexity. Not only might we us this for fault analysis, but also to improve designs/performance. Airlines even use limited telemetry to assist in lowering operations costs - this is why when we couldn't recover FDR's, we'd have some info that hinted at catastrophic failure. As a result there is more demand for airline telemetry than before.

FDR's absorb the firehose - actually there are separate performance recorders for obvious reasons - but in effect the same thing, as any data recorded will be analyzed likewise afterwards.

Telemetry bandwidth hasn't increased at Moore's law rate. Which is why the art of telemetry is actually getting harder.  You can never have enough data.
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Offline Robotbeat

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Re: SpaceX COTS Demo 1 Updates
« Reply #1324 on: 12/31/2010 04:57 am »
2 bytes of data gives you 64k analog resolution, so 1,000 samples per second would only be around 120KB raw data per minute if you had some nice clean software that only stored results.
 Been in this discussion with airliner folks who were convinced that you couldn't send real time system monitoring without using "Huge" amounts of bandwidth. You can pack a pretty impressive number of high resolution/rate analog readings into a small data stream if you're old enough to remember when efficiency counted and you didn't get to use 4 thousand lines of code to read a switch.

Now, imagine you have 70 such channels plus a couple of tri-axial accelerometers you want to sample at 20kHz.  On each engine.  And you have another hundred or so channels on the stage and FTS.  And you have a similar situation on the upper stage, just with one engine.  I make that at over 1.5GB/s.

It can add up when you have a few high-rate channels and when you have hundreds and hundreds of channels.
No, you're wrong.

You skipped two zeros.

It'd be 15MB/s based on what you just said.
((70*1000Hz+2*3*20000Hz)*9+300*20000Hz)*2Bytes = ~15MB/s
(you can easily check this in Google if you wish)
...(since you used "120KB raw data per minute")...
Wasn't me, that was Nomadd! :) I see what the confusion is, though. :)
Quote
Yes, you could store it on a UDMA Compact Flash card for the whole ascent.  I wouldn't want to try to find it in the ocean, however.
Agreed. However, my main point is that storing a lot or a little data makes very little difference in terms of volume or mass nowadays, which your own  analysis is in agreement with.
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Offline A_M_Swallow

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Re: SpaceX COTS Demo 1 Updates
« Reply #1325 on: 12/31/2010 08:12 am »
{snip}
Yes, you could store it on a UDMA Compact Flash card for the whole ascent.  I wouldn't want to try to find it in the ocean, however.

However I suspect that there are several aerospace engineers who would find designing a re-entry vehicle for a UDMA Compact Flash Card an interesting challenge.

Recoverable means that the little vehicle will probably have to float, not short out when exposed to sea water and transmit a homing signal.

Note: Solar cells can maintain intermittent radio transmissions during the day light hours for several weeks.

Since this is off topic any reply probably needs to go in its own topic.

Offline Nomadd

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Re: SpaceX COTS Demo 1 Updates
« Reply #1326 on: 12/31/2010 01:17 pm »
 Cast it in a block of bright orange epoxy foam held to the top of the stage with water soluble glue and add $200 worth of EPIRB hardware.
 That WWED shirt should have a picture of a pair of tin snips below the words.
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Offline Maverick

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Re: SpaceX COTS Demo 1 Updates
« Reply #1327 on: 01/03/2011 04:38 am »
The SpaceX successes are worthy to enter the Shuttle-heavy year in review articles :)

http://www.nasaspaceflight.com/2011/01/wrapping-up-2010-safety-success-eye-toward-future/

Offline Antares

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Re: SpaceX COTS Demo 1 Updates
« Reply #1328 on: 01/03/2011 06:21 am »
I thought the dragon page said they were on good ol' Mil Std 1553 and RS-422 also?

Those are onboard data buses, not telemetered/RF formats.
If I like something on NSF, it's probably because I know it to be accurate.  Every once in a while, it's just something I agree with.  Facts generally receive the former.

Offline starsilk

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Re: SpaceX COTS Demo 1 Updates
« Reply #1329 on: 01/04/2011 03:16 pm »
Press release from DLA Energy about the recent flight:

http://www.dla.mil/DLAPublic/DLA_Media_Center/PressRelease/PressReleasePrintable.aspx?ID=909

they were apparently the provider of the hypergolic fuels, and also provided logistics for recovery (presumably unused fuel cleanup / mitigation)

Offline TexasRED

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Re: SpaceX COTS Demo 1 Updates
« Reply #1330 on: 01/04/2011 03:39 pm »
I thought the dragon page said they were on good ol' Mil Std 1553 and RS-422 also?

Those are onboard data buses, not telemetered/RF formats.

yeah just the dragon page had all of them listed under the same C&T section so had me asking.


Offline Comga

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Re: SpaceX COTS Demo 1 Updates
« Reply #1331 on: 01/04/2011 04:16 pm »
Press release from DLA Energy about the recent flight:

http://www.dla.mil/DLAPublic/DLA_Media_Center/PressRelease/PressReleasePrintable.aspx?ID=909

they were apparently the provider of the hypergolic fuels, and also provided logistics for recovery (presumably unused fuel cleanup / mitigation)

Curious
DLA (which has a .MIL domain) provided "two propellants for the historic launch: dinitrogen tetroxide and monomethylhydrazine".  One would conclude that SpaceX obtained their LOX and RP-1 from another source, despite DLA Energy being a provider of those at KSC.

http://www.desc.dla.mil/DCM/Files/FY10%20Standard%20Price%20Letter%20%20Price%20Sheet%20Aug%2009_1.pdf

edit: Added link to DLA price list source
« Last Edit: 01/04/2011 08:58 pm by Comga »
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Online Lee Jay

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Re: SpaceX COTS Demo 1 Updates
« Reply #1332 on: 01/04/2011 04:32 pm »
Liquid Oxygen at $95/TN?  I'm assuming that "TN" doesn't mean "ton" or else LOX costs less than concrete, which would be a bit shocking.  Can someone help me out here?

Offline Robotbeat

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Re: SpaceX COTS Demo 1 Updates
« Reply #1333 on: 01/04/2011 04:43 pm »
Liquid Oxygen at $95/TN?  I'm assuming that "TN" doesn't mean "ton" or else LOX costs less than concrete, which would be a bit shocking.  Can someone help me out here?
LOx is incredibly cheap. LOx is made from air.
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Offline go4mars

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Re: SpaceX COTS Demo 1 Updates
« Reply #1334 on: 01/04/2011 04:54 pm »
LOx is made from air.

Do they use a centrifuge then?  I would have thought they would do electrolyis of water.  Either way, the price is probably mostly from the energy required to separate, chill, and truck it.
« Last Edit: 01/04/2011 04:55 pm by go4mars »
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Offline Robotbeat

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Re: SpaceX COTS Demo 1 Updates
« Reply #1335 on: 01/04/2011 04:57 pm »
LOx is made from air.

Do they use a centrifuge then?  I would have thought they would do electrolyis of water.  Either way, the price is probably mostly from the energy required to separate, chill, and truck it.
The cheapest way is fractional distillation of air. Anything else is a lot more expensive.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Online Lee Jay

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Re: SpaceX COTS Demo 1 Updates
« Reply #1336 on: 01/04/2011 05:06 pm »
Liquid Oxygen at $95/TN?  I'm assuming that "TN" doesn't mean "ton" or else LOX costs less than concrete, which would be a bit shocking.  Can someone help me out here?
LOx is incredibly cheap. LOx is made from air.

And huge amounts of energy and a large cryogenic plant.  Is it really $95 a ton?

Offline Comga

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Re: SpaceX COTS Demo 1 Updates
« Reply #1337 on: 01/04/2011 05:20 pm »
Liquid Oxygen at $95/TN?  I'm assuming that "TN" doesn't mean "ton" or else LOX costs less than concrete, which would be a bit shocking.  Can someone help me out here?
LOx is incredibly cheap. LOx is made from air.
And huge amounts of energy and a large cryogenic plant.  Is it really $95 a ton?
Remember, that's the price that SpaceX DIDN'T pay.  They must have an even less costly source, perhaps generating it on site.
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline Antares

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Re: SpaceX COTS Demo 1 Updates
« Reply #1338 on: 01/04/2011 05:23 pm »
LN2 and LO2 are made in air separation units.  The only recurring cost is electricity.
If I like something on NSF, it's probably because I know it to be accurate.  Every once in a while, it's just something I agree with.  Facts generally receive the former.

Offline starsilk

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Re: SpaceX COTS Demo 1 Updates
« Reply #1339 on: 01/04/2011 05:35 pm »
Press release from DLA Energy about the recent flight:

http://www.dla.mil/DLAPublic/DLA_Media_Center/PressRelease/PressReleasePrintable.aspx?ID=909

they were apparently the provider of the hypergolic fuels, and also provided logistics for recovery (presumably unused fuel cleanup / mitigation)

Curious
DLA (which has a .MIL domain) provided "two propellants for the historic launch: dinitrogen tetroxide and monomethylhydrazine".  Once would conclude that SpaceX obtained their LOX and RP-1 from another source, despite DLA Energy being a provider of those at KSC.

the caption on the photo is:

Quote
Powered by propellants procured by Defense Logistics Agency Energy, a Falcon 9 rocket carries a SpaceX Dragon spacecraft into orbit Dec. 8 from Cape Canaveral Air Force Station, Fla. Photo courtesy of SpaceX
(emphasis mine)

that doesn't square with the text in the actual press release, which talks about hypergols. maybe they thought the LOX/RP-1 was too boring to write a PR about?

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