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

[Jim]

No, water did not enter the pressure vessel. If it had then there would have been more damage and contamination of samples. Pristine blood and urine samples sitting in a bath of salt water would obviously contaminate things. I believe Suffredini even explicitly stated that water did not reach the freezers.

Huh?  Never said it was a lot of water, or that it reached the reached the freezers.  It doesn't take much water short something out. 

[Jim]

Also why in the world would they open up the capsule (there are no humans to remove) before they got the capsule up on deck and secured? If water actually got inside the pressure vessel then there would have to have been a leak in the pressure vessel which would be a much larger issue than losing the externally mounted power system.

Pressure equalization valve not hatch was hypothesized.

Is there a link about the power supply being outside the pressure vessel?

[mlindner]

Also why in the world would they open up the capsule (there are no humans to remove) before they got the capsule up on deck and secured? If water actually got inside the pressure vessel then there would have to have been a leak in the pressure vessel which would be a much larger issue than losing the externally mounted power system.

Pressure equalization valve not hatch was hypothesized.

Is there a link about the power supply being outside the pressure vessel?

Given insufficient information always assume the simplest answer until shown otherwise. Also given that Suffredini talked about several problems that occurred in flight with regard to computers and even other very minor issues, it would not make sense to avoid mentioning a more major issue. So unless you have direct evidence that states there was water intrusion into the pressure vessel, your point does not stand. You're inventing issues out of thin air.

[Jim]

Given insufficient information always assume the simplest answer until shown otherwise.

And that would be that water got in because most of the avionics are inside the pressure vessel.

[Lars_J]

Given insufficient information always assume the simplest answer until shown otherwise.

And that would be that water got in because most of the avionics are inside the pressure vessel.

Power systems != avionic systems. But we just don't know enough, so both of you are just guessing.

[mr. mark]

So, to put it simply, water got in through a faulty valve and shorted out the freezer. There was no damage to the freezer contents? (Hope that's right)

[Lars_J]

So, to put it simply, water got in through a faulty valve and shorted out the freezer. There was no damage to the freezer contents? (Hope that's right)

No, we don't know that. All we *know* is that:
A) the freezer lost power for a short while (apparently not enough to damage contents), and
B) there was water damage to some systems.

We don't *know* that those issues are 1) connected at all and if 2) the water penetrated the main pressure vessel. (some Dragon systems are in the unpressurized "service ring/section")

[mlindner]

Jim is just supposing that all the power equipment must be inside the pressure capsule because the avionics is and that because that must be the case then water must have gotten inside the pressure vessel.

In reality that is a contrived set up. Power must already run through the pressure vessel because the solar panels are on the trunk. Further, the trunk is attached to the bottom section of Dragon with most of the surface covered by the heat shield. The trunk is attached with clamps and connectors that all run to the lower unpressurized section of the trunk first. Even IF all the power regulation is inside the pressure vessel (unlikely because of the back and forth wiring required) there could easily still be exposed power connectors outside the trunk that run to things like the the parachute deploy, RCS thruster control, sensor bay, and any number of other things.

I actually wouldn't be surprised if all the avionics were outside the pressure vessel as well to allow more volume for cargo.

[go4mars]

Would it be easier from a heat rejection perspective to put power systems in the unpressurized area?  Or is there no meaningful difference?

[mlindner]

So, to put it simply, water got in through a faulty valve and shorted out the freezer. There was no damage to the freezer contents? (Hope that's right)

No, we don't know that. All we *know* is that:
A) the freezer lost power for a short while (apparently not enough to damage contents), and
B) there was water damage to some systems.

We don't *know* that those issues are 1) connected at all and if 2) the water penetrated the main pressure vessel. (some Dragon systems are in the unpressurized "service ring/section")

We actually DO know that they are connected. NASA directly stated that the freezers failed because of water intrusion into power related equipment that caused them to fail.

[Lars_J]

So, to put it simply, water got in through a faulty valve and shorted out the freezer. There was no damage to the freezer contents? (Hope that's right)

No, we don't know that. All we *know* is that:
A) the freezer lost power for a short while (apparently not enough to damage contents), and
B) there was water damage to some systems.

We don't *know* that those issues are 1) connected at all and if 2) the water penetrated the main pressure vessel. (some Dragon systems are in the unpressurized "service ring/section")

We actually DO know that they are connected. NASA directly stated that the freezers failed because of water intrusion into power related equipment that caused them to fail.

Alright, but my point 2 still stands. We don't know *where* the problem occurred, so it is meaningless to argue until an authoritative source can confirm or deny.

[Jim]

I actually wouldn't be surprised if all the avionics were outside the pressure vessel as well to allow more volume for cargo.

The avionics are in the base of the pressure vessel that is useless for cargo.

[wolfpack]

Would it be easier from a heat rejection perspective to put power systems in the unpressurized area?  Or is there no meaningful difference?

Think about environmental effects. Silicon semiconductors only work reliably from about -40C to +125C and they really hate radiation.

[mlindner]

See time at 34:42.

Sufferdini specifically states "[The power compnents] are in a lower portion of the Dragon that sees water at splashdown. [SpaceX] knew before that flight that the way the box is sealed, is not sealed well enough to prevent water intrusion."

So I think this pretty much settles the discussion.

[mlindner]

Would it be easier from a heat rejection perspective to put power systems in the unpressurized area?  Or is there no meaningful difference?

Think about environmental effects. Silicon semiconductors only work reliably from about -40C to +125C and they really hate radiation.

The cubesats I've worked on run off the shelf $6 microcontrollers in space. Work just fine. Occasionally see single event upsets, get rebooted, everything keeps working. Also except on orbits with very little sunlight temperatures generally stay between -10C and 50C

[wolfpack]

The cubesats I've worked on run off the shelf $6 microcontrollers in space. Work just fine. Occasionally see single event upsets, get rebooted, everything keeps working. Also except on orbits with very little sunlight temperatures generally stay between -10C and 50C

Sure, in LEO, but Dragon purports to be capable of more than that.

We are OT for launch updates, though. This should move to Falcon/Dragon discussion thread.

[beancounter]

You still need to get into the capsule for various jobs, plus access other areas on the capsule and trunk, which definately requires a clean room and bunny suits

Well if Elon wants to get to fly like commercial airliners do, then cleanrooms and bunnysuits need to be designed out of the systems or at least components etc, need to become sufficiently robust to eliminate the need for this.
Gotta say it does seem like excessive requirements but then, I have no experience with spaceflight so ...

[Chris Bergin]

31 posts in a row that were on a processing thread, when they should be in a discussion thread. Clipped and merged.

Come on people, it's not that hard to work out.

[Ben the Space Brit]

You still need to get into the capsule for various jobs, plus access other areas on the capsule and trunk, which definately requires a clean room and bunny suits

Well if Elon wants to get to fly like commercial airliners do, then cleanrooms and bunnysuits need to be designed out of the systems or at least components etc, need to become sufficiently robust to eliminate the need for this.
Gotta say it does seem like excessive requirements but then, I have no experience with spaceflight so ...

That is still a long way off.  Right now, spacecraft sensors and equipment are not at the level of robustness that they can tolerate shirt-sleeve maintenance the way that those on airliners can do (and I think that even some airliner equipment needs a degree of dirt/dust control during maintenance).

IMO, Dragon is not and never will reach that level.  I think it's at least a generation or maybe even two developmental generations before that point.

[IRobot]

You still need to get into the capsule for various jobs, plus access other areas on the capsule and trunk, which definately requires a clean room and bunny suits

Well if Elon wants to get to fly like commercial airliners do, then cleanrooms and bunnysuits need to be designed out of the systems or at least components etc, need to become sufficiently robust to eliminate the need for this.
Gotta say it does seem like excessive requirements but then, I have no experience with spaceflight so ...

That is still a long way off.  Right now, spacecraft sensors and equipment are not at the level of robustness that they can tolerate shirt-sleeve maintenance the way that those on airliners can do (and I think that even some airliner equipment needs a degree of dirt/dust control during maintenance).

IMO, Dragon is not and never will reach that level.  I think it's at least a generation or maybe even two developmental generations before that point.

Having a clean room means nothing. Many industrial processes, even with small companies, use clean rooms. And even bakers don't work in a shirt-sleeve environment, so IMO that is not a way to measure development.