SpaceX COTS Demo 2 Updates

[Jim]

Of course, in the period between Dragon escape capability being introduced and Dragon propulsive landing being introduced, Dragon will carry excess propellant to the ISS that could be used for reboost.

Of course, you wrong. No, you can't assume that.
A. Cargo Dragon is not the manned Dragon
b.  Those might not be available for the last cargo Dragon
c.  Might not matter how much propellant is carries, it still might not be doable.

[ugordan]

Suffredini said that Dragon may carry 800 lbs of cargo on COTS 2.

I've seen others on twitter report 800 kg. Which is is then?

Why not carry a more CRS-sized load?

Could be additional propellant margin for the extended maneuvering for C2/C3 objectives. Also, F9 needs to restart to carry Orbcomms to 700 km apogee so Dragon can't be maxed out.

[Lars_J]

Hardware, lots and lots of hardware:

http://www.nasa.gov/pdf/580727main_4%20-%20Lindenmoyer%20COTS%20Status_508.pdf

Lovely pictures.

I do see that there is at least the "starboard" window, here to the right of the hatch.  Perhaps the other window is there too, now uncovered by what may have been something temporary.  The suface looks different than in the pervious photos.

That's because these PDF photos are older than the other pictures, where an outer (white) is covering the insulation in the PDF pictures. The pictures we saw earlier with the "post-it notes" all over the surface are later in the assembly process.

[psloss]

Suffredini said that Dragon may carry 800 lbs of cargo on COTS 2.

I've seen others on twitter report 800 kg. Which is is then?

In the status briefing Mr. Suffredini said "up to 800 kilos."  (And he noted that the number was pre ULF-7.)

[ugordan]

Thanks.

[starsilk]

1.  I'm not sure I'd agree that the capability is 'not required'. there have been plans for a (US) ISS reboost module to cover the possibility of the Russian segment (or vehicles) being unable to do the job.

2.  seems like doing the work to 'certify' one of the new commercial US vehicles to do the job would be prudent (and it may be that Cygnus is better suited to the task, due to its shape).

1.  That was eons ago and not applicable to today.

well I'd say it's clearly more applicable *today* than it was ten years ago. now there's no Shuttle, no Progress (for a while), no ATV (for a while). that doesn't leave a whole heap of options. the onboard thruster is only useful as a very temporary solution, because it will wear out. it seems sensible to me to have a US solution for reboost.

2.  No, not if it is not viable.

we won't know if it's viable until someone crunches the numbers.

a.   shape has nothing to do with one or the other

cygnus shape is better because it's thrusters don't need to be angled.

b.  They don't carry propellant for reboost, only enough to do their mission.

add more propellant! there's obviously room for more in Dragon - the next COTS mission is carrying enough to do various exercises before actually docking. you have to assume Dragon is also being redesigned with bigger tanks *right now* to support their LAS solution. I'm sure cygnus could carry more too with a little redesign.

I'm not saying "lets attach the COTS dragon and fire away!". I'm just suggesting it would be a good idea to figure out how it could be done with a US solution, for situations just like the one we've found ourselves in today...

[Jim]

1.  well I'd say it's clearly more applicable *today* than it was ten years ago. now there's no Shuttle, no Progress (for a while), no ATV (for a while). that doesn't leave a whole heap of options. the onboard thruster is only useful as a very temporary solution, because it will wear out. it seems sensible to me to have a US solution for reboost.

2.  we won't know if it's viable until someone crunches the numbers.

3.  cygnus shape is better because it's thrusters don't need to be angled.

4.  add more propellant! there's obviously room for more in Dragon - the next COTS mission is carrying enough to do various exercises before actually docking. you have to assume Dragon is also being redesigned with bigger tanks *right now* to support their LAS solution. I'm sure cygnus could carry more too with a little redesign.

1.  No, it is not applicable today.  The Prop module was only there in case of a SM problem,early in the ISS formation.  It was not a long term solution.  Also, it was to be shuttle delivered and serviced.  Hence, it is not applicable to today.

2.   educated guess says no.

3.  Still doesn't matter.  Want to guess how the shuttle's thrusters were aligned?

4.    You can't just flip a switch and do it.   No, there isn't room on the Dragon.  Propellant is not carried in the pressurized compartment.
The cargo Dragon is not the same as the manned one.
it is not a little redesign for Cygnus or any spacecraft.  Adding tanks not a matter of fact task.  Cygnus is really two separate parts.  The cargo module is an add on to the spacecraft module.  The spacecraft module doesn't have places for more tanks.  Also, Taurus II doesn't have the performance for a larger Cygnus.

Modifying spacecraft is not something that is done willynilly on the spur of the moment.

Also, NASA can't just direct them to do it.  NASA is only buying cargo delivery services from them.  It would have to make a new contract for reboost services and openly compete it.

""lets attach the COTS dragon and fire away!".  is exactly what you are stating.

Who says we need  US solution.   The problem isn't that dire.  This is an ISS problem and not a US problem. Reboost is the Russian's job and they need to fix it.

[krytek]

In 2 years we could have VASIMR reboosting the ISS. How likely that really is I wouldn't know.

[Lobo]

Yes, Dragon is not equiped with that capability and neither is ISS equiped with the ability to get prop from the US segment and transfer it to the Russian segment.

Reboosting with Dragon from a CBM introducing many, many questions that need to be resolved (stress on stack, maneuver to attitude and power generation/cooling concerns, etc) at rather high cost and effort when it is not required.

As I mentioned earlier, ISS reboost can be performed with the Russian segment thrusters.

Could a special Dragon be fitted with a docking adptor in place of the CBM?  So it could dock with whichever docking port ATV and PRogress use for reboost?  Since Dragon is supposed to be reusable, SpaceX would only have to have one special one, and it could be for reboost missions specifically. 
It could be fitted with a special trunk with some draco thrusters for the reboost, or it could have the planned integraed pusher LAS system fueled and modified so it could fire precisely enough for reboosed purposes.  (I'd assume all of them coming on at once would be too powerful for reboost) It could fire a matched pair of them perhaps, for a more gentle, longer duration firing. 
In which case, it could be fitted with internal batteries, and not really even need the trunk with solar panels.  A trunk would just get in the way if it was using it's integraded thrusters to do the reboost.

I couldn't see all of that really being much of a problem if at some point in the future it became desirable to have Dragon do reboost.

[ugordan]

This is the COTS Demo 2 thread. Pull yourselves together people.

[Robotbeat]

Fitting Dragon with a Russian-style docking system would be incredibly complicated. Dragon currently berths. In order to dock with a Russian system, you have to ram it. Very different.

[Nomadd]

add more propellant! there's obviously room for more in Dragon - the next COTS mission is carrying enough to do various exercises before actually docking. you have to assume Dragon is also being redesigned with bigger tanks *right now* to support their LAS solution. I'm sure cygnus could carry more too with a little redesign.

 Why do you "have" to assume anything? The Dragon carries 1280kg fuel for the LAS already. Fuel you obviously don't need for orbital operations if you use the LAS.

[Chris Bergin]

Locked. Don't have time to mod it, so you can all look at those being off topic and frown at them for a while.

[Chris Bergin]

Still busy, but I can't leave this locked, so here's the deal. Get this back on COTS-2/3, keep it on topic, and self police it like Ugordan tried to do if someone tries to take it off topic.

Don't make me call Nanny 911

[DaveH62]

Thanks Chris
On topic I hope.
Has the supply payload been increased? I thought I read that the upcoming cots 2-3 demo will now include hundreds of kilos of supplies. Anyone know if that is accurate? If so, is this an increase in scope, and possibly more funding for Spacex?

[Lars_J]

The only word from NASA has been that they had a budget of 800kg for cargo to the station in the combined COTS2/3 flight, but they were probably not going to use all of it. The Progress failure might however make them use up more of that.

That's what I understood from the NASA press conference yesterday.

[Geron]

Well then Nasa is really getting a better deal with SpaceX. They even get cargo on these combined demo missions, in the beginning there wasn't going to be cargo right? Is this just a way to sweeten the pot for them?

When you compare the orbital deal to the spacex deal, just how much more are we paying for orbital cargo compared to spacex cargo?

[ugordan]

When you compare the orbital deal to the spacex deal, just how much more are we paying for orbital cargo compared to spacex cargo?

That will depend on how much each CRS flight actually carries. The CRS contract calls for a minimum of 20 metric tons in total, at 1.6B for SpaceX and 1.9B for OSC.

[manboy]

Hardware, lots and lots of hardware:

http://www.nasa.gov/pdf/580727main_4%20-%20Lindenmoyer%20COTS%20Status_508.pdf

Lovely pictures.

I do see that there is at least the "starboard" window, here to the right of the hatch.  Perhaps the other window is there too, now uncovered by what may have been something temporary.  The suface looks different than in the pervious photos.

And look at that unpresurized volume.  How they plan to fit the LAS Super Dracos in there is beyond me.

There's something beautiful about seeing a CBM on Dragon, it just seems to makes me a little more optimistic about the future.

In 2 years we could have VASIMR reboosting the ISS. How likely that really is I wouldn't know.

Its 2014 according to Aviation Week.

The only word from NASA has been that they had a budget of 800kg for cargo to the station in the combined COTS2/3 flight, but they were probably not going to use all of it. The Progress failure might however make them use up more of that.

That's what I understood from the NASA press conference yesterday.

I believe this is the press conference in question (if anyone else is curious)

[mr. mark]

This just in off the Spacex, SpaceXer, Twitter feed...

"SpaceX will deliver hundreds of kilograms of cargo for crew supplies when Dragon berths with the Space Station later this year".

Does not sound like a cheese wheel this time.