Author Topic: SpaceX Falcon 9/Dragon COTS Demo (C2+) PRE LAUNCH UPDATES (PART 2)  (Read 111114 times)

Offline Space Pete

The beta angle isn't an on-off switch, so what makes the beta limit for Dragon the same as for ISS? Is it designed to exactly the same limit and no more?

As far as power generation goes, the only way to give Dragon adequate power during high beta periods would be to:
A) Give Dragon's solar arrays beta rotation capability, which would involve a serious redesign, increasing cost and complexity.
B) Point Dragon toward the Sun using its thrusters, which, as I explained in the article, would present its own issues, such as Dragon being out of attitude for rendezvous burns, and thermal issues.

Regarding thermal issues, Dragon was built to comply with ISS thermal requirements. It could have been built to higher requirements, but as with the solar arrays, upgrading would add cost and complexity.

Which makes me wonder: How would DragonLab handle thermal issues? And would the crewed Dragon (or any vehicle with solar arrays) be precluded from making an emergency undocking and landing in a high beta period?
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Offline robertross

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ISS schedule slips Dragon launch to May 19 future manifest outlook - by Pete Harding:

http://www.nasaspaceflight.com/2012/05/iss-schedule-dragon-launch-19-may-future-manifest-outlook/


That was an awesome article Mr. ISS, well done!

This site has some top notch writers, I tell you.
Remembering those who made the ultimate sacrifice for our rights & freedoms, and for those injured, visible or otherwise, in that fight.

Offline docmordrid

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Agreed!!  Nicely done Pete, nicely done.
DM

Offline AndyX

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Agreed! This site is brilliant. The open forum threads are busy and great. The articles are top class.

I'm so happy I'm supporting the site via my L2 membership, especially as the C2+ L2 Special is amazing, and because of the NASA and SpaceX people posting in there, plus the other stuff, as I'm currently watching a L2 video that's about as crazy cool as it gets. I mean, WTH!! ;D Why didn't I find this site sooner!

But yes, the article is great as we can use that if this does slip again past the 19th.

I wonder if they'll do another static fire to trim down the potential issues so to avoid the chance of a scrub.

Offline MP99

The beta angle isn't an on-off switch, so what makes the beta limit for Dragon the same as for ISS? Is it designed to exactly the same limit and no more?

As far as power generation goes, the only way to give Dragon adequate power during high beta periods would be to:
A) Give Dragon's solar arrays beta rotation capability, which would involve a serious redesign, increasing cost and complexity.
B) Point Dragon toward the Sun using its thrusters, which, as I explained in the article, would present its own issues, such as Dragon being out of attitude for rendezvous burns, and thermal issues.

Regarding thermal issues, Dragon was built to comply with ISS thermal requirements. It could have been built to higher requirements, but as with the solar arrays, upgrading would add cost and complexity.

Thanks, until I started drawing triangles, I hadn't appreciated the 50-75% "cosine losses" (**) at 60-75o beta angles. Helps explain why they'd need much bigger panels if they wanted to fly during the cutout.

I note, with humour, that the wiki article on beta angle says Shuttle could launch during high beta periods as long as ISS was out of beta cutout for docking. The humour being a great big "citation needed" sticker next to it, so we know what to make of that. :o (And solar panels weren't the issue for Shuttle, anyway).



BTW, for anyone else struggling to picture the beta angles, I found this excellent old flash animation. It's from before construction was complete, so you need to ignore the "high beta" animation on the 3rd page (it says XVV is now flown at all times, but couldn't be sustained during construction):-

http://spaceflight.nasa.gov/station/flash/start.swf

cheers, Martin

(**) I suspect that's not the correct terminology.

Edit: "insolation" -> "cosine losses".
« Last Edit: 05/06/2012 08:55 AM by MP99 »

Offline ceauke

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Thanks for that animation link Martin. It highlighted a misunderstanding that I had with the orbital mechanics of satellites. :-s

Why is the orbital plane changing in relation to the sun? I thought that changing the plane requires huge amounts of energy, so I would have assumed that the beta angle should stay constant. I'm clearly wrong but I'm missing some basic understanding.

One the flat earth with the satellite path over it, I thought the shift in the path is because of the earth spinning. But it seems that the orbital plane of the satellite is spinning too. Why is that? ??? Is it changing with the 'seasons' as earth orbits the sun?

Online ugordan

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Why is the orbital plane changing in relation to the sun?

If the orbital plane was fixed with respect to the stars, it would still change as Earth orbits the Sun as the Sun would change position with respect to the stellar background.

However, another effect comes into play here and its responsible for the rotation of the orbital plane around the Earth's axis as seen in that animation. See below.

Quote
I thought that changing the plane requires huge amounts of energy, so I would have assumed that the beta angle should stay constant.

Changing *inclination* requires energy, this rotation you see only changes the *plane* of the orbit while keeping inclination the same. As you can imagine, you can have many orbits with the same inclination without them actually lying in the same orbital plane.

Quote
One the flat earth with the satellite path over it, I thought the shift in the path is because of the earth spinning. But it seems that the orbital plane of the satellite is spinning too. Why is that? ???

The effect is called nodal regression and is due to the fact the Earth is not a perfect sphere but is bulged at the equator. Each time an orbiting object approaches the equatorial crossing, it feels a slightly bigger pull toward the equator. Once it passes the equator, it pulls it back slightly more so the effect cancels out as far as orbital inclination is concerned, but the orbital groundtrack ends up being shifted slightly to the west if the orbit is prograde. This slowly rotates the plane of ISS orbit around the Earth's axis, clockwise if you look above the north pole. It's not a continuous rotation, but more like a slight "jump" westward each time the orbit crosses the equator.
« Last Edit: 05/06/2012 10:57 AM by ugordan »

Offline TJL

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With the launch now scheduled to occur at "night", weather permitting, will it be possible to view it in the northeast sections of the United States as it enters orbit?
Thanks.

Offline MP99

Thanks for that animation link Martin. It highlighted a misunderstanding that I had with the orbital mechanics of satellites. :-s

Thanks, I though it was very clear.


Why is the orbital plane changing in relation to the sun? I thought that changing the plane requires huge amounts of energy, so I would have assumed that the beta angle should stay constant. I'm clearly wrong but I'm missing some basic understanding.

Superb explanation to be found here:-
http://forum.nasaspaceflight.com/index.php?topic=27289.msg829755#msg829755

cheers, Martin

Offline Andy USA

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No trim required, and the orbital plan items and such are fine, but just a reminder to some of the other posts that we have both a launch updates thread (this) and a discussion thread (http://forum.nasaspaceflight.com/index.php?topic=28486.0) so let's be careful. Thanks.

Offline Orbiter

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With the launch now scheduled to occur at "night", weather permitting, will it be possible to view it in the northeast sections of the United States as it enters orbit?
Thanks.

This should probably belong in the viewing thread, but I would imagine so yes, just not as bright as a Space Shuttle launch.

Orbiter
Attended space missions: STS-114, STS-124, STS-128, STS-135, Atlas V "Curiosity", Delta IV Heavy NROL-15, Atlas V MUOS-2, Delta IV Heavy NROL-37, Falcon 9 CRS-9, Falcon 9 JCSAT-16, Atlas V GOES-R, Falcon 9 SES-11, Falcon Heavy Demo.

Offline Space Pete

So I thought I'd make a list of the available C2+ launch opportunities for the foreseeable future (determined using +3 days from known dates, and factoring in known constraints).

May 19 (Current target)
May 22
May 25
May 28
<Beta cutout June 3 to June 13> (Precludes launch on May 31 as Dragon would be in free-flight on June 3.)
June 13
June 16
<Atlas V on CCAFS range for June 18 launch> (Precludes launch on June 19 due to range reconfig.)
June 22
June 25
<Delta IV on CCAFS range for June 28 launch>
<ISS schedule/beta angle issues through September 3>

So, that's four opportunities in May, followed by four in June, followed by a likely slip into September (assuming no ISS manifest changes).

Here's hoping Dragons have nine lives! :)
« Last Edit: 05/07/2012 04:47 PM by Space Pete »
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Offline corrodedNut

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More photos of the late-load test on March 2nd:

http://mediaarchive.ksc.nasa.gov/detail.cfm?mediaid=59219

Or just: http://mediaarchive.ksc.nasa.gov/search.cfm?cat=225 and go to page 4



« Last Edit: 05/07/2012 10:04 PM by corrodedNut »

Offline iamlucky13

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Regarding thermal issues, Dragon was built to comply with ISS thermal requirements. It could have been built to higher requirements, but as with the solar arrays, upgrading would add cost and complexity.

Which makes me wonder: How would DragonLab handle thermal issues? And would the crewed Dragon (or any vehicle with solar arrays) be precluded from making an emergency undocking and landing in a high beta period?

DragonLab isn't constrained by proximity to the ISS. I can only presume that if Dragon can handle the range of conditions from full sunlight + full earthshine + full ISS shine down to full shadow while being restricted in orientation, then it can handle them away from the ISS and not restricted in orientation.

As for crewed Dragon, my instinct is to say the duration during which they'd have limited orientation during an emergency undock should be short enough they can't soak up too much heat, but I can't confirm that.

My second thought on the matter is that crewed Dragon is not necessarily simply cargo Dragon with a docking adapter. SpaceX may have further improvements to its power and cooling/heating capacity planned.

Offline corrodedNut

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New update at SpaceX:

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

Same as earlier reports, but now *officially* on the updates page.
« Last Edit: 05/08/2012 09:12 PM by corrodedNut »

Offline Space Pete

Cupola now all set up for the Dragon capture (notice the CCP on the front of the RWS in the bottom-left).

Picture credit Don Pettit.
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Offline ChrisC

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More photos of the late-load test on March 2nd:

http://mediaarchive.ksc.nasa.gov/search.cfm?cat=225 and go to page 4

VERY interesting.  Thanks!
« Last Edit: 05/08/2012 10:03 PM by ChrisC »
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Offline mr. mark

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SpaceX is back at the 10 days to launch window again. It will get interesting from here on.

Offline ChefPat

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When is the next FRR?
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Offline AndyX

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I think Chris will be outlining the latest in an article and what's to come via L2, which is really excellent section of coverage for C2+, really is.

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