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

[Space Pete]

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.

[dcporter]

Sorry but without a reference I can't buy this: SpaceX made his own solar panels in house, obviously freely picking in the huge knowledge base of Solar City. I personally doubt the panels, quite surely made from commercial silicon cells, are that expensive.

So said, I'm sure that a "only battery" Dragon could be considered (not necessarily done!): cheaper, lighter, simpler.

In the pic, widely circulating image of in house testing of the panels.

The forum has a quote feature that is easier and makes reading your post a straightforward process rather than an exercise.

Some things are a little more expensive in space, some things are a lot more expensive. Solar panels for space are dramatically more expensive. Two reasons: First, since weight is precious, panel efficiency is crucial, and eking out the extra performance above commodity grade costs a great deal more money (similar to, and for similar reasons as, getting the "best" CPU in your computer costs way more than getting the regular grade one).

The second reason is that the solar panels are sitting out in the harsh vacuum of space, and need to be substantially radiation-hardened - another expensive proposition for solar panels.

(Edit: rad hard may be less important on these very short trips. Thanks mm!)

Also... you don't think Solar City manufactures its own panels in a factory somewhere in LA do you? They're experts at buying commodity solar panels, which probably excludes them from the spacecraft business entirely.

[mmeijeri]

Rad hardening shouldn't be important for relatively short missions (days to months).

[AJA]

We have had waaaay too much speculation on the valves. (I say this as one of the guilty members). Don't we have a picture of the system? I haven't found one yet.

[AnalogMan]

Both options require T-joints from the main He-line to the tanks. Only difference is having check valve in the main line or in the line from T-joint to the tank.

That's the point.

Yes? Does not mean you require any other length of line from the T-joint to the tank except the check valve. If you really want to compact things machine the check valve and T-joint into same body. edit: and if you want to compact things even further with redundancy, machine T-joint and the check valve quad redundancy into same body.

The shuttle orbiter used integrated quad check valves in the helium pressurisation lines for the RCS & OMS systems (graphic courtesy L2).

The serially connected pair of check valve modules are only commoned with the other pair at the main input/output ports - that is to say the mid-points of each pair are isolated from each other.  This arrangement allows the valve modules to be individually leak-checked using the two test ports provided during spacecraft processing.

[AJA]

Because they don't deem it as newsworthy.  It is minutia.

Ah yes, I forgot - updates on mission critical events are boring. What people really want to see is videos of SpaceX employees dancing to hip hop music, and such like.

But Jim, wouldn't disclosing all information serve to indicate that the employees are giddy about EVERYTHING they do? (Rightfully) Show how dedicated and excited the team is? It's a missed packaging opportunity if anything. I don't think a tweet costs that much - unless of course, they think tweeting too frequently drives followers away..

[yg1968]

Here is the full webcast videos of the launch from NASA and SpaceX:

[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.

[mr. mark]

More concern about SpaceX propulsion. We had a roll problem on Falcon 9 flight one due to a faulty roll control thruster on the second stage. On flight 3 we had the engine one shut down and on the current flight we had thruster problems on Dragon. Seems as though a through review of all propulsion systems needs to be done.

[Kabloona]

More concern about SpaceX propulsion. We had a roll problem on Falcon 9 flight one due to a faulty roll control thruster on the second stage. On flight 3 we had the engine one shut down and on the current flight we had thruster problems on Dragon. Seems as though a through review of all propulsion systems needs to be done.

These are normal "teething" problems for a new system, and the best way to find them is to fly and fix as needed. A bunch of engineers sitting in a room "reviewing" drawings and documents is not going to find anything.

The systems have already been through PDR, CDR, etc, and any issues that were identifiable via the design review process have already been caught. Those that slipped through the review process, eg the vent line impinging on the roll control thruster, are the ones that have to be identified and fixed during the first few flights. Engineers are fallible humans too, and not every potential issue can be identified by reviewing drawings.

Fly it, fix it, move on.

[R7]

I assume these are diaphragm tanks, so no way for NTO to migrate into the He plumbing

..unless the diaphragm has developed a leak.

In that scenario, three tanks would have had to leak NTO past their diaphragms and into their respective He presuurization lines

Not necessarily if NTO from one failed tank manages to leak into the pressurization line. Yeah, it shouldn't be able to do it, there's the check valve, but is He check valve compatible with NTO, does not degrade seals or anything? If there's no major pressure difference across the check valve the sealing force is just the spring load which is not that great.

Frozen condensate or contaminant in the He lines, or stuck check valve(s) much more plausible, IMO.

Agree on He contaminant. Three physically defective valves while otherwise nominal working conditions ... aren't those things tested time and again before installing. Major quality control failure if so, then again so is 'clumpy' He too.

[jabe]

These are normal "teething" problems for a new system, and the best way to find them is to fly and fix as needed. A bunch of engineers sitting in a room "reviewing" drawings and documents is not going to find anything.

i agree with that.. many reasons why I think Spacex has done it cheaper is that the build , test and fly rather than build,TEST TEST TEST then fly.  I am amazed they have  done so well  with the F9 and dragon with so few problems.  hope this bodes well  for other commercial space companies.
my 2  cents
jb

[Step55]

More concern about SpaceX propulsion. We had a roll problem on Falcon 9 flight one due to a faulty roll control thruster on the second stage. On flight 3 we had the engine one shut down and on the current flight we had thruster problems on Dragon. Seems as though a through review of all propulsion systems needs to be done.

The roll control problem on the second stage was caused by an actuator failure. There was nothing wrong with the Turbine exhaust nozzle "thruster". Was the engine shutdown not on flight 4?
Nasa and spacex just did a thorough review of the Merlin propulsion system.

[mr. mark]

More concern about SpaceX propulsion. We had a roll problem on Falcon 9 flight one due to a faulty roll control thruster on the second stage. On flight 3 we had the engine one shut down and on the current flight we had thruster problems on Dragon. Seems as though a through review of all propulsion systems needs to be done.

The roll control problem on the second stage was caused by an actuator failure. There was nothing wrong with the Turbine exhaust nozzle "thruster". Was the engine shutdown not on flight 4?
Nasa and spacex just did a thorough review of the Merlin propulsion system.

Correction you are right, it's flight 4. Still need to get the bugs out of the system. Let's hope 9V1.1 goes well.

[FinalFrontier]

More concern about SpaceX propulsion. We had a roll problem on Falcon 9 flight one due to a faulty roll control thruster on the second stage. On flight 3 we had the engine one shut down and on the current flight we had thruster problems on Dragon. Seems as though a through review of all propulsion systems needs to be done.

The roll control problem on the second stage was caused by an actuator failure. There was nothing wrong with the Turbine exhaust nozzle "thruster". Was the engine shutdown not on flight 4?
Nasa and spacex just did a thorough review of the Merlin propulsion system.

There is no issue with "spacex propulsion"

What your seeing here are, by the way relatively minor, issues with totally separate systems and totally separate departments.

This is normal for a new launch vehicle and spacecraft. In fact I would say its abnormal as the amount of problems we have seen so far are relatively low by comparison to previous vehicles.

That being said what your seeing is normal "bell curve" type failures (don't know what I mean google weibel curve). So its to be expected.


And if you think these issues are "alot of problems" consider shuttle during the first 10 years of its lifetime.

[Mike_1179]

To be fair, is it a relatively "minor" problem if it caused LOM of a secondary payload and on the next flight a missed rendezvous?

Just trying to keep a little perspective.  The fact that they haven't lost a primary mission because of these is an interesting mix of luck, appropriate margins and good work.

Fun to watch though

[Lar]

To be fair, is it a relatively "minor" problem if it caused LOM of a secondary payload and on the next flight a missed rendezvous?

Just trying to keep a little perspective.  The fact that they haven't lost a primary mission because of these is an interesting mix of luck, appropriate margins and good work.

Fun to watch though

A missed rendezvous? IF they don't make a rendezvous eventually then maybe. IF there is time sensitive stuff on board that can't stand a 1 day or 2 day delay (which is what it looks like it's going to be, barring more problems) then maybe.

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)

[john smith 19]

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.

As the maiden launch of Ariane 5 showed, leaving redundant code in a flight system, even if it does nothing, is a bad idea.
 

[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?

[adrianwyard]

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

@ 49m29s


It could be just discoloration, but perhaps buckling, or at least localized heating.

It was hard to see in CRS-1, but there is something similar in demo flight video:

@09m09s