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

[Lar]

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.

[Lars_J]

In other prop news: Did anyone else think the Mvac nozzle looked a little peculiar right after stage two shutdown?

I have noticed it before - it is most likely just discoloration caused by the turbine exhaust.

[Robotbeat]

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.

[Mike_1179]

But a missed rendezvous??? Premature exclamation man!

This stuff is normal. As another poster said, if anything, abnormally FEW problems.... Chill! Enjoy the ride and stop worrying so much. (I admit, I was worried right after launch up till about 3 PM eastern but they fixed it)

Yes, they missed it.  They were supposed to be there today, and they are not, because they could not make a burn in time to get there.  They still haven't gotten there because they have to prove that it won't happen again.

So they did miss the rendezvous that was planned.  This was supposed to use a quicker approach to ISS.  If there was an experiment in there which required one day before it had to get to ISS or data would be lost (not saying there is) then this experiment would be gone.

The plan was to get to ISS in one day, that did not happen because something went wrong.  Saying "this only proves how awesome SpaceX is!!!11!1!" means you are losing sight of what is important.

If you pay for FedEx overnight delivery, and the truck catches fire, but because of some heroic and clever actions by the FedEx people you package survives and is delivered intact by a day late, it's still late.

By the way, I'm not worried, I'm following this with as much excitement as anyone else here.  I think SpaceX is doing great work.  I'm trying not to let my excitement get in the way of being objective, however.

[mduncan36]

But a missed rendezvous??? Premature exclamation man!

This stuff is normal. As another poster said, if anything, abnormally FEW problems.... Chill! Enjoy the ride and stop worrying so much. (I admit, I was worried right after launch up till about 3 PM eastern but they fixed it)

Yes, they missed it.  They were supposed to be there today, and they are not, because they could not make a burn in time to get there.  They still haven't gotten there because they have to prove that it won't happen again.

So they did miss the rendezvous that was planned.  This was supposed to use a quicker approach to ISS.  If there was an experiment in there which required one day before it had to get to ISS or data would be lost (not saying there is) then this experiment would be gone.

The plan was to get to ISS in one day, that did not happen because something went wrong.  Saying "this only proves how awesome SpaceX is!!!11!1!" means you are losing sight of what is important...

I frequently go to Central America, specifically Honduras, where we have a popular expression that goes "This is Honduras." That's what you have to keep in mind where time and schedule are subject to the very different world around you. It might be a good idea to alter perspective a bit and keep in mind that "This is spaceflight" and it doesn't run on rails or work with the precision of Fedex. Virtually all of it is new no matter how many times it's been done and it is always subject to a very different set of rules than what we are accustomed to. We're dealing with situations where all's well that ends well. Roll with it and be glad when you achieve a successful outcome no matter how it happens.

When this flight is in the books it will be recalled as adversity overcome and lessons learned. That is success in spaceflight.

[R7]

If you pay for FedEx overnight delivery, and the truck catches fire, but because of some heroic and clever actions by the FedEx people you package survives and is delivered intact by a day late, it's still late.

Hey the truck wasn't on fire! Actually the truck performed beautifully this time, no blown pressure losses in tires. Truck delivered a van for the final delivery lap, but three of van's four wheels were initially stuck. Careful and controlled clutch pumping solved the problem (for now). Here at FedX we call it minor incident, so be ready we are rolling in the package!

[Robotbeat]

Did NASA pay extra for overnight delivery? If you order 5 business day delivery, often get the package in 3 days but one time have to wait until the 4th day, you have no right to complain.

NASA is used to 3-day rendezvous, so this is still early for them. It's got to be incredibly frustrating for people to pick on every little glitch as counting against them. What matters is that the payload gets safely to ISS within a reasonable time (and back to the ground). Since there's extra margin built in, it's fine for NASA if Falcon 9 loses an engine on the way up, if the thrusters have a glitch, if a computer loses sync, etc. These systems are redundant for a reason because what matters is delivering the payload successfully within a reasonable time frame not whether there are non-LOM glitches in the meantime.

If you were just trying to minimize number of glitches, you'd have single-string everything and you'd have a high LOM rate but otherwise, hey, no glitches! 

[psloss]

It's got to be incredibly frustrating for people to pick on every little glitch as counting against them.

Peanut galleries come with the territory.

[R7]

Since there's extra margin built in, it's fine for NASA if Falcon 9 loses an engine on the way up, if the thrusters have a glitch, if a computer loses sync, etc. These systems are redundant for a reason because what matters is delivering the payload successfully within a reasonable time frame not whether there are non-LOM glitches in the meantime.

Redundancy didn't save the day here. It would have been LOM if the pod glitches would not have gone away by valve yanking. Redundant system would not have required it to proceed with the mission.

[Robotbeat]

Since there's extra margin built in, it's fine for NASA if Falcon 9 loses an engine on the way up, if the thrusters have a glitch, if a computer loses sync, etc. These systems are redundant for a reason because what matters is delivering the payload successfully within a reasonable time frame not whether there are non-LOM glitches in the meantime.

Redundancy didn't save the day here. It would have been LOM if the pod glitches would not have gone away by valve yanking. Redundant system would not have required it to proceed with the mission.

Agreed, but redundancy probably did contribute to this non-LOM glitch. They have a lot more valves than if they had just a single ox and single fuel tank.

[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.

cheers, Martin

[MP99]

2. CO2 -- since most of He production goes from natural gas, some processing schemes give He with substantial CO2 content. However, it is difficult to imagine that CO2 would form a solid ice blocking valve.

Well the He is released from very high pressure reservoir, it expands, does work, cools, no? But does it cool enough to freeze CO2, dunno. Moisture more likely would freeze.

Agree on both comments.
Also, about moisture -- it is not only freezes more easily, it is also pretty easy to get as contaminant. It can get in He at production, transportation, and at propellant/pressurizer loading just as well.

Wouldn't it be simple enough to chill the He so that all water vapour freezes out before loading it to the spacecraft?

Not so sure how you'd ensure no water is already in the prop system before you begin loading - long flush with high temperature dry nitrogen?

cheers, Martin

[MP99]

For anyone interested, here's some best available images (1080p @ fullscreeen) of the HRSGFs visible in the Dragon Trunk just after separation.

SpaceX have apparently been trying to keep images of the Trunk + cargo secret - pretty pointless in the end.

BTW, Pete - those are 657x488, not 1080p. Still look good, though. - thanks for posting.

cheers, Martin

[R7]

redundancy probably did contribute to this non-LOM glitch.

Unknown without root cause and system schematics. Sure would be nice to see up-to-date diagram how the RCS is plumbed. Is there anything known for sure about Dragon RCS system, on top of what you can deduce from published photos? Wiki speaks of double redundancy, but reading more carefully it seems to refer to individual thrusters, might mean only thruster specific valves, not the pressurization system. *waving arms wildly* 

[Lars_J]

For anyone interested, here's some best available images (1080p @ fullscreeen) of the HRSGFs visible in the Dragon Trunk just after separation.

SpaceX have apparently been trying to keep images of the Trunk + cargo secret - pretty pointless in the end.

No, it has not been secret. At least on this forum we have seen schematics for how the trunk cargo would be configured ( http://forum.nasaspaceflight.com/index.php?topic=28006.msg874090#msg874090 ), and the in-flight images mathed that perfectly.

And ingeneral we don't get pictures of every ISS bound payload, even if it would be neat. (Perhaps in L2?)

[mrmandias]

My guess is that NASA is not paying SpaceX for overnight delivery.  I hope not, anyway.  Since that would be an extremely expensive requirement with little benefit.

But a missed rendezvous??? Premature exclamation man!

This stuff is normal. As another poster said, if anything, abnormally FEW problems.... Chill! Enjoy the ride and stop worrying so much. (I admit, I was worried right after launch up till about 3 PM eastern but they fixed it)

Yes, they missed it.  They were supposed to be there today, and they are not, because they could not make a burn in time to get there.  They still haven't gotten there because they have to prove that it won't happen again.

So they did miss the rendezvous that was planned.  This was supposed to use a quicker approach to ISS.  If there was an experiment in there which required one day before it had to get to ISS or data would be lost (not saying there is) then this experiment would be gone.

The plan was to get to ISS in one day, that did not happen because something went wrong.  Saying "this only proves how awesome SpaceX is!!!11!1!" means you are losing sight of what is important.

If you pay for FedEx overnight delivery, and the truck catches fire, but because of some heroic and clever actions by the FedEx people you package survives and is delivered intact by a day late, it's still late.

By the way, I'm not worried, I'm following this with as much excitement as anyone else here.  I think SpaceX is doing great work.  I'm trying not to let my excitement get in the way of being objective, however.

[john smith 19]

Agreed, but redundancy probably did contribute to this non-LOM glitch. They have a lot more valves than if they had just a single ox and single fuel tank.

AFAIK Every RCS system has used multiple nozzle clusters fed by separate tanks.

[R7]

Wouldn't it be simple enough to chill the He so that all water vapour freezes out before loading it to the spacecraft?

Possibly, as long as it doesn't clog up your freezer Maybe a cascade system similar to make dry compressed air.

Not so sure how you'd ensure no water is already in the prop system before you begin loading - long flush with high temperature dry nitrogen?

That ought to work. If nothing implodes you could evacuate the system before filling.

[Joffan]

... although it is obviously inconvenient if a particular day is nominated for rendezvous and the plans for activities on board the station need to be rescheduled at the last minute.

But that's life. And not unusual or especially challenging for the ISS team, I'd imagine.

[Lar]

Did NASA pay extra for overnight delivery? If you order 5 business day delivery, often get the package in 3 days but one time have to wait until the 4th day, you have no right to complain.

NASA is used to 3-day rendezvous, so this is still early for them. It's got to be incredibly frustrating for people to pick on every little glitch as counting against them. What matters is that the payload gets safely to ISS within a reasonable time (and back to the ground). Since there's extra margin built in, it's fine for NASA if Falcon 9 loses an engine on the way up, if the thrusters have a glitch, if a computer loses sync, etc. These systems are redundant for a reason because what matters is delivering the payload successfully within a reasonable time frame not whether there are non-LOM glitches in the meantime.

If you were just trying to minimize number of glitches, you'd have single-string everything and you'd have a high LOM rate but otherwise, hey, no glitches! 

Roger that.

I fly, a lot. So I tend to use airlines as my metric for how I would LIKE (eventually!!!!) things to operate for this transport type. May never get there, but that's my yardstick. I harp on gas and go, I harp on not burning up pieces of the pad, and etc.

That said...

Airlines are late. A LOT.  Their contract of carriage says "we will get you from point A to Point B ... eventually. And we might lose your bag, and if we do, we will usually find it and get it to you, eventually... but if we don't find it... here is what we are going to pay you, per pound... "  And you know what? We all use airlines a lot. If they are late, if they lose my bag, **I** might see it as a fail, but technically (see contract of carriage) it's not a fail!!!! I deal with it. And I still fly.

We don't know exactly what the contract between SpaceX and NASA says. but I bet it doesn't guarantee arrival at ISS at any particular time.

----

Another thing about airlines and airplanes. They don't tell us much about what is really going on. If there's an issue SOMETIMES they tell us, but often they just say "a mechanic is on board, hang a bit" ... then they say "OK problem sorted, here we go"

SpaceX tells us less than NASA did. Drives me crazy just as it does when Delta tells me less than I wanted to know... But I deal.

----

And, finally... Part of them not telling me stuff is not telling me that they had failures that don't matter. I know for SURE that planes fly with defects, that don't threaten LOM, all the time. My armrest, my seat light, my recline, all of those things have defects from time to time. And I know other systems that are not visible, ... they ALSO have defects. The judgment call is not "is the aircraft perfect before we take off?" it's... "is this aircraft safe enough, even with the failures in some redundant systems, to go?" ... some of these systems may have failures, one out of 4 check valves down or whatever, but as long as they stiil have adequate redundancy, they go.

We in the peanut gallery DO need to chill. It's not rabid fannishness to point this out. Any space vendor deserves the same consideration for things that are redundant, sorted out, and worked around. Not just SpaceX. Heck, even Boeing and ULA, and Lockheed

I need to learn this better myself I guess. but I'm not alone.