SpaceX COTS Demo 2/3 Updates (THREAD 2)

[corrodedNut]

Does anyone know how the late-load test went?

[cuddihy]

That to me looks like a late May launch for COTS-2/3.
Full 6 person crew
No other traffic over a 6 week period
Time after the orbit raising to let phasing drift into tolerance
Are these, in fact, signficant scheduling considerations?

I don't understand the orbit phasing consideration--isn't the Dragon trajectory adjusted to meet whatever is needed for the phasing the ISS is in at the point of launch?

[Jim]

I don't understand the orbit phasing consideration--isn't the Dragon trajectory adjusted to meet whatever is needed for the phasing the ISS is in at the point of launch?

No, phasing determines long the Dragon will take to catch up to the ISS.  It relates to the phase angle between the ISS and Dragon at launch.
Also, the Dragon can only fly so low in a stable orbit, so that fixes a maximum phase angle to allow rendezvous within a fixed period.  Also, there is a drive to standardize rendezvous process.

[wolfpack]

That to me looks like a late May launch for COTS-2/3.
Full 6 person crew
No other traffic over a 6 week period
Time after the orbit raising to let phasing drift into tolerance
Are these, in fact, signficant scheduling considerations?

I don't understand the orbit phasing consideration--isn't the Dragon trajectory adjusted to meet whatever is needed for the phasing the ISS is in at the point of launch?

As I understand it, phasing means how far "behind" the ISS Dragon is when it becomes orbital. The ISS ground track and F9's trajectory are roughly equal when F9 launches. ISS is "speeding away" and Dragon is "catching up". In order to "catch up", Dragon needs a lower orbit with a shorter period than ISS's orbit. Then, when it gets "close enough" and "underneath" ISS, Dragon does a short burn to raise its orbit up to the altitude and period of ISS. If Dragon is really far "behind" ISS when it achieves orbit, then it will need to lower its own orbit even more to "get faster". Problem is, you can only go so low before you're getting into drag from the exosphere that will work to slow you down and "ellipticize" (for lack of a better word) your orbit. Then you'll have to expend propellant to fight this effect. That's not an efficient way to do things.

So, the launch window for ISS resupply depends heavily on the spacecraft's capabilities. In the case of Shuttle it was around 10 minutes. For F9/Dragon, it could be a whole lot narrower.

[Jim]

So, the launch window for ISS resupply depends heavily on the spacecraft's capabilities. In the case of Shuttle it was around 10 minutes. For F9/Dragon, it could be a whole lot narrower.

Not quite true.  The window was not so much phase angle but in or out track which requires yaw steering

[Comga]

So, the launch window for ISS resupply depends heavily on the spacecraft's capabilities. In the case of Shuttle it was around 10 minutes. For F9/Dragon, it could be a whole lot narrower.

That is not necessarily correct.  The ten minute window for Shuttle was limited by the ability to change the plane.  (Like Jim said.) Also, orbits aren't made so low that they fight the atmosphere, unless you consider long term altitude maintinance of the ISS.

Simple geometry and orbital calcs show that the period of the ISS at 400 km is around 92.6 minutes.  For a 300 km chase orbit it's 90.5 minutes and for an absolutely minimum orbit of 200 km its 88.5 minutes.  If the orbital crossing and launch occurred just before the ISS passed the ideal point, the chasing vehicle would have to do one full additional orbit if the rendezvous was restricted to catching up in a lower orbit. It would take 2.85 days to catch up a full orbit at 300 km, and 1.40 days at 200 km.   

PS Thanks Jim!

[cuddihy]

Does anyone know how the late-load test went?

Spaceflightnow has a mission update on Dragon that discusses what the testing was -- basically of the mobile cleanroom that allows Dragon to be opened & loaded all the way to the pad, while the spacecraft remains integrated to the F9 and horizontal.

http://www.spaceflightnow.com/falcon9/003/status.html

Somewhat fortuitously, it's placed directly below the ATV update which goes into detail about the two week delay ATV will need to de-integrate the launcher and payload undo the fairing, open the ATV, place a special access lift, etc just to fix a broken cargo strap.

Clearly this is one case where having no fairing and multiple access hatches makes a big difference for flexibility.

*updated to correct my misunderstanding that ATV required demating to access.

[Jim]

the hangar is hardly a pristine processing facility

[cuddihy]

So, the launch window for ISS resupply depends heavily on the spacecraft's capabilities. In the case of Shuttle it was around 10 minutes. For F9/Dragon, it could be a whole lot narrower.

That is not necessarily correct.  The ten minute window for Shuttle was limited by the ability to change the plane.  (Like Jim said.) Also, orbits aren't made so low that they fight the atmosphere, unless you consider long term altitude maintinance of the ISS.

Simple geometry and orbital calcs show that the period of the ISS at 400 km is around 92.6 minutes.  For a 300 km chase orbit it's 90.5 minutes and for an absolutely minimum orbit of 200 km its 88.5 minutes.  If the orbital crossing and launch occurred just before the ISS passed the ideal point, the chasing vehicle would have to do one full additional orbit if the rendezvous was restricted to catching up in a lower orbit. It would take 2.85 days to catch up a full orbit at 300 km, and 1.40 days at 200 km.   

PS Thanks Jim!

Thanks Jim and Comga for great explanations. I actually understand the orbital mechanics of Dragon catchup and phasing, my question is operational.  What about the ISS orbit needs to come 'in tolerance' to launch Dragon? ISS longitude of the ascending node?

[Jim]

there are no restrictions on the ISS.

[woods170]

Somewhat fortuitously, it's placed directly below the ATV update which goes into detail about the two week delay ATV will need to de-integrate the launcher and payload undo the fairing, open the ATV, place a special access lift, etc just to fix a broken cargo strap.

ATV will not be de-integrated from the launcher. Only the fairing will be removed. Then access will be gained thru the docking-hatch with the LCAM lift. This is identical to the actual late loading (minus the fairing removal), which took place after ATV had been integrated onto Ariane-5.

[ugordan]

Does anyone know how the late-load test went?

Don't know, but there are several images of a Glacier unit being prepared for transport to LC-40 for the demonstration at the KSC media archive:

http://mediaarchive.ksc.nasa.gov/detail.cfm?mediaid=58207
http://mediaarchive.ksc.nasa.gov/detail.cfm?mediaid=58208
http://mediaarchive.ksc.nasa.gov/detail.cfm?mediaid=58209
http://mediaarchive.ksc.nasa.gov/detail.cfm?mediaid=58210
http://mediaarchive.ksc.nasa.gov/detail.cfm?mediaid=58211
http://mediaarchive.ksc.nasa.gov/detail.cfm?mediaid=58212
http://mediaarchive.ksc.nasa.gov/detail.cfm?mediaid=58213

[Jim]

Does anyone know how the late-load test went?

Don't know, but there are several images of a Glacier unit being prepared for transport to LC-40 for the demonstration at the KSC media archive:

Brings back memory of Spacehab days

[Prober]

the hangar is hardly a pristine processing facility

Jim gets ready for the white glove test..hehheh

[mr. mark]

Thinking about this flight...This will be the first time that the US. will have an unmanned cargo delivery vehicle. In the end they will have two (SpaceX, Orbital) So this will be a flight of firsts. First "commercial", first US unmanned cargo and it will be the first time that Russia, ESA, US and Japan will all be using unmanned vehicles for cargo delivery, a new standard.

[Jkew]

My twitter feed detected a new SpaceX post:

Behind the scenes photo from the making of the Dragon panorama http://pic.twitter.com/7TzYPs0G

This must have been taken many months ago, if this was the COTS2/3 Dragon.

The following blog describes the panorama shoot in detail with a few interesting shots:
http://www.picturebubbles.com/blog/2012/01/the-making-of-the-spacex-dragon-capsule-picturebubbles-virtual-tour.html

[HIP2BSQRE]

So, the launch window for ISS resupply depends heavily on the spacecraft's capabilities. In the case of Shuttle it was around 10 minutes. For F9/Dragon, it could be a whole lot narrower.

That is not necessarily correct.  The ten minute window for Shuttle was limited by the ability to change the plane.  (Like Jim said.) Also, orbits aren't made so low that they fight the atmosphere, unless you consider long term altitude maintinance of the ISS.

Simple geometry and orbital calcs show that the period of the ISS at 400 km is around 92.6 minutes.  For a 300 km chase orbit it's 90.5 minutes and for an absolutely minimum orbit of 200 km its 88.5 minutes.  If the orbital crossing and launch occurred just before the ISS passed the ideal point, the chasing vehicle would have to do one full additional orbit if the rendezvous was restricted to catching up in a lower orbit. It would take 2.85 days to catch up a full orbit at 300 km, and 1.40 days at 200 km.   

PS Thanks Jim!

NASA recently said that they wanted a demo flight to last three days---Since it might take 2.85 days to catch up at 300 km...is there where NASA might have got this requirement?? 

[Norm38]

In layman’s terms, Dragon is likely to carry around 1,000lbs of various supplies – such as clothes and food – to the crew of the International Space Station.

I'm surprised they're sending lots of empty bags and only 1000 lbs of stuff. Why not fill the empty bags with jugs of water?

If they don't carry max payload, then they have a much greater fuel margin.  In the event that orbital insertion is a bit off for some reason, that could be the difference between making it to the ISS or not.
It's a demo mission.  If all they bring up is a bag of M&Ms, but it does get there, then they hit all their performance goals for this flight.

I also figure their ideal down mass isn't maxed out either.

[RocketJack]

In layman’s terms, Dragon is likely to carry around 1,000lbs of various supplies – such as clothes and food – to the crew of the International Space Station.

I'm surprised they're sending lots of empty bags and only 1000 lbs of stuff. Why not fill the empty bags with jugs of water?

If they don't carry max payload, then they have a much greater fuel margin.  In the event that orbital insertion is a bit off for some reason, that could be the difference between making it to the ISS or not.
It's a demo mission.  If all they bring up is a bag of M&Ms, but it does get there, then they hit all their performance goals for this flight.

I also figure their ideal down mass isn't maxed out either.

How do you know this isn't flying "max payload"?

[Ben the Space Brit]

In layman’s terms, Dragon is likely to carry around 1,000lbs of various supplies – such as clothes and food – to the crew of the International Space Station.

I'm surprised they're sending lots of empty bags and only 1000 lbs of stuff. Why not fill the empty bags with jugs of water?

If they don't carry max payload, then they have a much greater fuel margin.  In the event that orbital insertion is a bit off for some reason, that could be the difference between making it to the ISS or not.
It's a demo mission.  If all they bring up is a bag of M&Ms, but it does get there, then they hit all their performance goals for this flight.

I also figure their ideal down mass isn't maxed out either.

How do you know this isn't flying "max payload"?

At a guess, the reason for believing that C2/3 will be flying light is simply becaues of the nature of the mission.  The objective is to rendezvous and berth with the ISS, not deliver the maximum payloayd to the station.  Because of that, you will want to maximise your chances of reaching the ISS and being able to carry out the required proximity ops.  That means maximum margin on launcher and RCS delta-v and that means low-mass.

I have no doubt that, as they gain confidence with the vehicle, the mass numbers will go up towards the nominal maximums, but not before Merlin-1d is in service.