Author Topic: SpaceX Falcon 9/Dragon CRS-2 SpX-2 MISSION GENERAL DISCUSSION (Read 379849 times)

Lar · « **Reply #460 on:** 03/01/2013 07:49 pm »

Quote from: Elmar Moelzer on 03/01/2013 06:57 pm

I am a software developer and copy paste errors are common. It would explain why something works for one thing and not the others (because e.g. they cant work if the code does not match the hardware). It is all pure speculation at this point anyway.

Soon as I heard 1 worked and the rest didn't that was my thought too... Looks like, from the presser, that it was some check valve issue

Star One · « **Reply #461 on:** 03/01/2013 07:57 pm »

When it gets to the ISS will the crew on-board be able to do any kind of inspection of Dragon that would be useful to SpaceX's investigations?

Comga · « **Reply #462 on:** 03/01/2013 08:00 pm »

Quote from: Comga on 02/28/2013 09:54 pm

Quote from: Lars_J on 02/28/2013 09:30 pm
Quote from: Comga on 02/28/2013 08:57 pm
From the press conference:

"If solar arrays fail they may have enough battery power to make one berthing attempt."

So if they achieve several day 2 rendezvous and berthings, why not do away with the solar panels? They might want to upgrade the batteries somewhat, but these would be recovered and potentially reused.

Why reduce your chance of mission success by removing a critical source of power?

To reduce cost and increase payload.
A battery upgrade has to be less mass than the solar panels, mechanisms, and pontoons.
One could even increase reliability by removing the solar panel system with its mechanisms and wiring.
Apparently that source of power is not "critical".

Not saying SpaceX should, just that they could.

in
http://forum.nasaspaceflight.com/index.php?topic=31239.msg1020087#msg1020087

newQ: how much time did the solar array buy, and what would this have meant if this was a crewed flight?

Elon - at first we were going to get to 2 before deploying but the temp in the array actuators was dropping and a sim said maybe we should deploy before it got too cold... as it turns out extending the arrays slowed the rotation rate of the craft (like an ice skater extending arms)... Crewed version won't have solar arrays, just a really big battery pack (unless it is long duration)

and I was just "thinking out loud"

mmeijeri · « **Reply #463 on:** 03/01/2013 08:03 pm »

Quote from: Jorge on 03/01/2013 08:01 pm

No, the prop system is outside the pressurized cabin and uses toxic propellants.

Is there anything they could see from the robot arm that can't be seen from the cameras inside the various Dragon compartments? Actually, are there any such cameras on Dragon itself, or just on the Falcon?

Star One · « **Reply #464 on:** 03/01/2013 08:04 pm »

Quote from: mmeijeri on 03/01/2013 08:03 pm

Quote from: Jorge on 03/01/2013 08:01 pm
No, the prop system is outside the pressurized cabin and uses toxic propellants.

Is there anything they could see from the robot arm that can't be see from the cameras inside the various Dragon compartments? Actually, are there any such cameras on Dragon itself, or just on the Falcon?

Could the arm maneuver it so it could be examined photographed, if this was any help?

Kabloona · « **Reply #465 on:** 03/01/2013 08:04 pm »

Quote from: Jorge on 03/01/2013 08:01 pm

Quote from: Star One on 03/01/2013 07:57 pm
When it gets to the ISS will the crew on-board be able to do any kind of inspection of Dragon that would be useful to SpaceX's investigations?

No, the prop system is outside the pressurized cabin and uses toxic propellants.

The good news is SpaceX will be able to disassemble the He pressurant system, assuming safe Dragon return, and probably find out exactly what happened...unlike last propulsion anomaly...

Ben the Space Brit · « **Reply #466 on:** 03/01/2013 08:08 pm »

Fortunately, unlike most cargo resupply vehicles, SpaceX should get this one back (all going reasonably well).

The propulsion team at Hawthorne are no doubt already being scrambled and briefed to tear this spacecraft's RCS fuel system apart and find out what went wrong. Remember, the same fuel system will power Dragonrider's LAS, so no-one wants a tank pressurisation failure of this kind again, if at all possible.

Ares67 · « **Reply #467 on:** 03/01/2013 08:08 pm »

Just in at nasa.gov:

SpaceX: Dragon's Four Thruster Pods Online

Fri, 01 Mar 2013 10:04:57 PM UTC+0100

SpaceX says all four of Dragon's four thruster pods are now online. Dragon is not expected to berth at the International Space Station tomorrow as planned. NASA and SpaceX are assessing the next steps and berthing opportunities.

manboy · « **Reply #468 on:** 03/01/2013 08:09 pm »

Quote from: MondoMor on 03/01/2013 08:06 pm

Quote
Elon Musk ‏@elonmusk

Thruster pods one through four are now operating nominally. Preparing to raise orbit. All systems green.

Woot!

Danderman · « **Reply #469 on:** 03/01/2013 08:11 pm »

Assignment for everyone: study the concept of orbital precession. There will be a quiz on Monday.

Lars_J · « **Reply #470 on:** 03/01/2013 08:12 pm »

Woot indeed!

yg1968 · « **Reply #471 on:** 03/01/2013 08:13 pm »

The post-launch press conference is available as an mp3 file here:
http://spaceref.biz/2013/03/spacex-falcon-9-launches-on-second-space-station-resupply-mission.html

AJA · « **Reply #472 on:** 03/01/2013 08:18 pm »

Quote from: Danderman on 03/01/2013 08:11 pm

Assignment for everyone: study the concept of orbital precession. There will be a quiz on Monday.

Gladly. Any recommended places to start? I've spent way too long just nodding my head in agreement when dynamicists mention constraints.

Brian Copp · « **Reply #473 on:** 03/01/2013 08:24 pm »

It is quite possible that some of the oxidizer was frozen and locked up the valves. NTO has a relatively high freezing point (18F at 1 atm). Maintaining it in liquid form is not a trivial matter, especially in a pressure fed system. If something is wrong with the system that heats the propellants, they could be in serious trouble.

smoliarm · « **Reply #474 on:** 03/01/2013 08:48 pm »

If 3 of 4 He valves got blocked or stuck - this does not look like manufacturing flaw ... That's way too much

Also, listening to Elon's answers, I got impression that it is not a software problem. Well, then it could be **bad** helium:
In general, industrial high-pressure He could have 3 type of contaminants - well, may be more, but from my experience I know 3.
1. Rotary pump oil contamination in He was very common problem in our lab, but it was LONG time ago. I don't think they use this kind of pumps to compress He anymore.
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.
3. Dust -- some He bottles had very fine dust blocking our bleeding valves dead.

So, there are couple things SpaceX could do before the Dragon's return - check their He stock tanks for dust / organic contaminants; and - check the other Dragon's He pressure bottles for manufacturing dust inside.

plank · « **Reply #475 on:** 03/01/2013 08:58 pm »

So no est on berthing?

mtakala24 · « **Reply #476 on:** 03/01/2013 08:58 pm »

A lot of speculating on the UPDATES thread, so I'll post here:

I would say that those few seconds spent flying through some clouds do not have any effect whatsoever to the tanks that are inside the spacecraft. The clouds, if they would contain enough moisture, would deposit their moisture on the outer skin. I fail to see them having much effect during that limited time. Also, the aerodynamic heating flying through max-q would counter the effect.

Robotbeat · « **Reply #477 on:** 03/01/2013 09:12 pm »

Quote from: Kabloona on 03/01/2013 08:04 pm

Quote from: Jorge on 03/01/2013 08:01 pm
Quote from: Star One on 03/01/2013 07:57 pm
When it gets to the ISS will the crew on-board be able to do any kind of inspection of Dragon that would be useful to SpaceX's investigations?

No, the prop system is outside the pressurized cabin and uses toxic propellants.

The good news is SpaceX will be able to disassemble the He pressurant system, assuming safe Dragon return, and probably find out exactly what happened...unlike last propulsion anomaly...

Indeed! Recovery (essential for reuse) has its advantages.

R7 · « **Reply #478 on:** 03/01/2013 09:20 pm »

Even if Dragon would have frozen solid flying through moist clouds the check valves should still work.

Kabloona · « **Reply #479 on:** 03/01/2013 09:26 pm »

Root cause still unknown, but wouldn't be the first time check valves implicated in spacecraft propulsion anomalies. Loss of Mars Observer in '93 was attributed to probable hypergol leakage past check valves during long cruise to Mars.