SpaceX Falcon 9/Dragon CRS-2 SpX-2 MISSION GENERAL DISCUSSION

[Robotbeat]

Ya know, I don't know if we're maxed out up or not. We're probably close, on this particular flight, to being max mass.

Well, that was useful and certainly the definitive statement you made it out to be.

I never claimed it was "definitive". LegendCJS's original statement was "about the maximum for the F9 v1.0" and if the president of the company says "probably close", that is good enough for me.

Note also Suffredini's follow-up to Shotwell which, best I can make out (?)...
Shotwell: I don't know if we're maxed out up or not. We're probably close, on this particular flight, to being max mass.
Suffredini: That's an understatement.

I like Suff, he's funny. Wonder if he's miffed about the mass or just trying to keep everyone honest.

No, he didn't say "that's an understatement." I listened to it several times, and if you increase the volume, clearly he says "that's what I understand."

So far, they are what, a bit behind on the 20 metric tonnes total, right? Or am I misremembering the mass on CRS-1 ?

It'd be dumb if they tried to "get ahead" with the total mass on early flights and on a vehicle that gets ~half of the performance of the v1.1. The rational decision would be to assign less mass to the early flights and add as much prop margin as you can (you can't fill the tanks up more than full, but by having less payload, you have much more delta-v margin).

[Lar]

Note also Suffredini's follow-up to Shotwell which, best I can make out (?)...
Shotwell: I don't know if we're maxed out up or not. We're probably close, on this particular flight, to being max mass.
Suffredini: That's an understatement.

I like Suff, he's funny. Wonder if he's miffed about the mass or just trying to keep everyone honest.

No, he didn't say "that's an understatement." I listened to it several times, and if you increase the volume, clearly he says "that's what I understand."

So far, they are what, a bit behind on the 20 metric tonnes total, right? Or am I misremembering the mass on CRS-1 ?

It'd be dumb if they tried to "get ahead" with the total mass on early flights and on a vehicle that gets ~half of the performance of the v1.1. The rational decision would be to assign less mass to the early flights and add as much prop margin as you can (you can't fill the tanks up more than full, but by having less payload, you have much more delta-v margin).

I'm kinda deaf so I will take your word for it... As for the mass, I agree, it would be silly to push too hard in early days, especially with a higher performing bird in the wings. Still I don't think they are actually very far behind...

[Paul Howard]

Lots and lots of info from Chris in the article that went on site just now.
http://www.nasaspaceflight.com/2013/03/resilient-crs-2-dragon-pursuit-iss-sunday-berthing/

[manboy]

Ya know, I don't know if we're maxed out up or not. We're probably close, on this particular flight, to being max mass.

Well, that was useful and certainly the definitive statement you made it out to be.

I never claimed it was "definitive". LegendCJS's original statement was "about the maximum for the F9 v1.0" and if the president of the company says "probably close", that is good enough for me.

Note also Suffredini's follow-up to Shotwell which, best I can make out (?)...
Shotwell: I don't know if we're maxed out up or not. We're probably close, on this particular flight, to being max mass.
Suffredini: That's an understatement.

It sounds like he's saying "That's understand".

[LouScheffer]

So far, they are what, a bit behind on the 20 metric tonnes total, right? Or am I misremembering the mass on CRS-1 ?

To get 20 mt of upmass on 12 flights they need to average 1667 kg/flight.  The first was 454 kg, this one 1050 kg.   So on the next 10 flights they need to average (20,000 - 1,504)/10 = 1850 kg/flight.

If the Falcon 1.1 works anywhere near as well as expected, this should be no problem.

[Lar]

Are the propellant/oxidiser tanks, or the Draco thrusters, cross fed? I had assumed not and thus I am wondering how realistic some of the "Dragon can deorbit on just one pod with careful jockeying" was... if not crossfed you have 1/4 the total deltavee available and that's IT. Given that you'd have to do a lot of weird gyrations, which might use more propellant, I just wonder if it was realistic or if we fans were making stuff up to feel good.

[Robotbeat]

Dragon has a ton of extra propellant than it needs. Holding and station-keeping near ISS, several aborts and retries... That all uses up a lot of propellant. All you have to do to deorbit is get your perigee low enough that drag brings you down.

[jcm]

Guys we get tweets from the space X team members. it's not that big of a deal if we don't get it on the official Twitter account.

Apart from @elonmusk, whose tweets do you recommend for actual technical content?

I like Mollie McCormick and Matt Sachtler

https://twitter.com/Molliway and  https://twitter.com/mattsachtler

I would be interested in others too.

And @kenners ... There are some others but they usually don't have much as far as details.

Much appreciated, thanks.

Still no substitute for official play by play with burn times, distances etc
like one had in the old days  #whenIwasalad

[joek]

So far, they are what, a bit behind on the 20 metric tonnes total, right? Or am I misremembering the mass on CRS-1 ?

Depends on how you count.  The original CRS contract was for a total of 12 flights with 20 tonnes up and an option for 3 tonnes down.*  With this Spx-2 flight they'll have delivered a total of 2024kg up (assuming unpressurized 373kg is correct) and 2935kg down.

With 10 flights following, that would mean an average of ~1798kg up-mass/flight.  Assuming F9v1.1 is anywhere close to its stated performance, they shouldn't have a problem hitting the up-mass requirement, and appear to be far exceeding down-mass requirements.


* While the CRS contract states 3mt down, the original RFP from back in 2008 has a a total down-mass requirement of 8mt or ~1.5mt/year.

[yg1968]

Shotwell: I don't know if we're maxed out up or not. We're probably close, on this particular flight, to being max mass.
Suffredini: That's an understatement.

I'm pretty sure he said "That's what I understand."

That would make more sense and welcome to the forum!

[joek]

@johnmoe -- Thanks.  Yes, "That's what I understand." fits (original post updated).

[peter-b]

Gwynne's comments in the pre-launch press conference suggest that SpaceX are aiming for 20 tonnes total up + down.

[Robotbeat]

Gwynne's comments in the pre-launch press conference suggest that SpaceX are aiming for 20 tonnes total up + down.

Someone has suggested 60 up/down. Where does 60 come from?

[Targeteer]

Houston passed during the daily planning conference that grapple will be half and hour early at 1100 GMT

[stone]

Someone has suggested 60 up/down. Where does 60 come from?

This was a quote from a press conference of the last launch to the ISS. I think a women said it around minute 14.

[MP99]

No, it wasn't known before. See this post on the cost of the solar arrays:
http://forum.nasaspaceflight.com/index.php?topic=30385.msg1020178#msg1020178

Posts in that general area indicate it was.

However I'll note that space rate panels will have a load of parts Earth panels will not. Specifically all the space rated mechanical bits to deploy/steer them.

Going battery only also eliminates knock on parts, like latches, actuators, deployment mechanisms plus all the associated testing/QC costs. That sounds like a pretty good trade.

Downside. You will definitely need a separate software build for Crewed Vs Cargo Dragon. Array deployment seems a pretty big event and a bunch of code will be associated with it, some of which will probably trigger/inhibit other stuff.

Dragon can plainly operate on battery only, as Gwynne said it might be able to go all the way to berthing if the panels failed to deploy.

That was only the case on this launch opportunity because the phase angle allowed an early berthing attempt. In general, this will not be the case.

Thanks - yeah I should have said that

I think she said something like 18 hours. I was trying to make the point (but poorly worded), that Dragon is currently designed to be able to operate (as a contingency) without solar panels.

cheers, Martin

[jcm]

So how did they compress an hour from last night's planned schedule?
Did the approach burns change, or they just skipped time at the hold points?

Edit: at least partly the burns, I think, because it was already an hour
ahead at the 250-meter point

[jak Kennedy]

Congrats SpaceX and NASA. The cool aid is sweet this morning ;-)

[Lar]

Is it just me or did the time from capture to berthing seem a bit longer than last time?  Last time was controlled from ISS and this time from the ground, right?

[kch]

Congrats SpaceX and NASA. The cool aid is sweet this morning ;-)

Enjoying the coffee!  (see party thread)