Orion Spacecraft Q & A

[Raj2014]

Hello everyone,

It has been a long time since I posted here. I started this topic because I got a message about starting a new topic, so this topic is to continue an old one, https://forum.nasaspaceflight.com/index.php?topic=11997.160.

Has there been any changes made to the Orion EM-1 from the Orion EFT-1? If yes, what are the changes? 

[rayleighscatter]

The main heat shield has been changed to a monolithic form as opposed to many individual parts. The thermal tiles on the side (look like Space Shuttle tiles) will be getting a highly reflective coating instead of the bare tiles seen on EFT-1.

[Raj2014]

The main heat shield has been changed to a monolithic form as opposed to many individual parts. The thermal tiles on the side (look like Space Shuttle tiles) will be getting a highly reflective coating instead of the bare tiles seen on EFT-1.

Why have they decided to change to those items? Will it reduce mass, manufacturing time and cost? What will the coating do? 

[brickmack]

Its basically a new design. EFT-1 didn't have a service module at all, so EVERYTHING there is new. On the CM, they changed the heat shield to be more easily manufactured (its now made in tiles like the bottom of Dragon, instead of a single piece), the backshell TPS has a new coating on it for additional protection and on-orbit thermal control, the pressure vessel has been redesigned to need fewer welds (lower mass and easier manufacturing), changes to the parachutes and inflatable floatation devices have been made based on issues encountered on EFT-1, the computers are new, and it will carry some life support test equipment.

[Raj2014]

Its basically a new design. EFT-1 didn't have a service module at all, so EVERYTHING there is new. On the CM, they changed the heat shield to be more easily manufactured (its now made in tiles like the bottom of Dragon, instead of a single piece), the backshell TPS has a new coating on it for additional protection and on-orbit thermal control, the pressure vessel has been redesigned to need fewer welds (lower mass and easier manufacturing), changes to the parachutes and inflatable floatation devices have been made based on issues encountered on EFT-1, the computers are new, and it will carry some life support test equipment.

Fascinating. With the heat shield made of titles, how do they solve the issue of a title or titles disconnecting from the C.M?   

[Jim]

Fascinating. With the heat shield made of titles, how do they solve the issue of a title or titles disconnecting from the C.M?   

No different than the shuttle

[Raj2014]

Fascinating. With the heat shield made of titles, how do they solve the issue of a title or titles disconnecting from the C.M?   

No different than the shuttle

Is that not a problem that needs to be solved? Do not want the heat to burn the inside of the C.M and destroy it. Already there has been a past incident of missing titles. I do not want to see it happen again. 

[DaveS]

Fascinating. With the heat shield made of titles, how do they solve the issue of a title or titles disconnecting from the C.M?   

No different than the shuttle

Is that not a problem that needs to be solved? Do not want the heat to burn the inside of the C.M and destroy it. Already there has been a past incident of missing titles. I do not want to see it happen again. 

Debonded tiles (not titles) were only a problem very early in the program. Once they had perfected the tile-bonding the only concerns were actual damage. Part of the issue was the water-proofing agent used early in the program  which was of the shelf 3M ScotchGuard sprayed directly onto the tiles.

This didn't work too well with the adhesive used to bond the tiles to the skin of the orbiters which caused such issues that STS-51C was reassigned from Challenger to Discovery because Challenger had tile adhesion problems severe enough to warrant changing the bodyflap on Challenger with the one originally intended for Atlantis which was undergoing final assembly in Palmdale.

After these issues they came up with a new tile water-proofing agent (Dimethylethoxysilane) which is injected directly into each tile with a needleless gun in the OPF. This pretty much took care of the tile adhesion issues once and for all.

[Lars-J]

Fascinating. With the heat shield made of titles, how do they solve the issue of a title or titles disconnecting from the C.M?   

No different than the shuttle

Is that not a problem that needs to be solved? Do not want the heat to burn the inside of the C.M and destroy it. Already there has been a past incident of missing titles. I do not want to see it happen again.

Dragon has been flying with a tiled heat shield for a while now. No tiles have been lost, as far as I know. That aspect of Orion does not worry me at all.

Once a heat shield reaches a certain size, a monolithic piece becomes impractical.

[woods170]

Fascinating. With the heat shield made of titles, how do they solve the issue of a title or titles disconnecting from the C.M?   

No different than the shuttle

Is that not a problem that needs to be solved? Do not want the heat to burn the inside of the C.M and destroy it. Already there has been a past incident of missing titles. I do not want to see it happen again.

Dragon has been flying with a tiled heat shield for a while now. No tiles have been lost, as far as I know. That aspect of Orion does not worry me at all.

Once a heat shield reaches a certain size, a monolithic piece becomes impractical.

The funny thing is that LockMart was warned in advance that a monolithic heat shield for Orion would likely have cracking issues due to it's size in combination with the use of an injected honeycomb structure. Those warnings were partly based on experience with cracking issues of the Apollo primary heatshield.
Despite the warnings, LockMart went with the monolithic design anyway, only to experience cracking issues during manufacture. Those required repairs, delaying the delivery of the primary heat shield and triggering an R&D effort for a segmented heat shield.
During EFT-1 post-flight inspections more cracks were found. That only served to confirm the change in direction towards a segmented primary heat shield.

A monolithic heat shield has a further disadvantage: it requires an immensely stiff, and thus heavy, carrier structure. Now that Orion will have a segmented heat shield the carrier structure has been re-designed as well. It doesn't have to be as stiff as the old design. Consequently, the new design is quite a bit less heavy than the previous one.

[Lars-J]

And the even bigger irony is (IMO) that NASA rejected PICA because it would have to be applied using tiles.  And now they are back to Avcoat with tiles.   

[woods170]

And the even bigger irony is (IMO) that NASA rejected PICA because it would have to be applied using tiles.  And now they are back to Avcoat with tiles.   

No, that was not the primary reason to reject PICA. The primary reason was lack of experience base for large-scale application of PICA. It had been used on missions only one time before: a small-scale application of PICA as the primary heatshield material for the Stardust sample return probe.

While SpaceX had, at the time of selection of Avcoat for Orion in 2009, completed development of PICA-X, there was no large-scale flight experience with PICA(-X) yet. Therefore, NASA went for the one material they knew much about: Avcoat.

[Raj2014]

Since the Dragon capsules has used PICA-X titled heat shields for several launches. Why has Lockheed Martin or NASA not decided to use it for the Orion's heat shield?

[Jim]

Since the Dragon capsules has used PICA-X titled heat shields for several launches. Why has Lockheed Martin or NASA not decided to use it for the Orion's heat shield?

PICA-X is Spacex propriety material and is not available

[baldusi]

Since the Dragon capsules has used PICA-X titled heat shields for several launches. Why has Lockheed Martin or NASA not decided to use it for the Orion's heat shield?

PICA-X is Spacex propriety material and is not available

Did NASA tried to request SpaceX to be the heatshield subcontractor for Orion and they flat denied or they have simply not made the RFQ and is not a pure NASA product?

[whitelancer64]

Since the Dragon capsules has used PICA-X titled heat shields for several launches. Why has Lockheed Martin or NASA not decided to use it for the Orion's heat shield?

PICA-X is Spacex propriety material and is not available

Did NASA tried to request SpaceX to be the heatshield subcontractor for Orion and they flat denied or they have simply not made the RFQ and is not a pure NASA product?

The NASA Authorization Act of 2010 specified the use of existing contractors for SLS and Orion.

[Lars-J]

PICA-X is Spacex propriety material and is not available

Did NASA tried to request SpaceX to be the heatshield subcontractor for Orion and they flat denied or they have simply not made the RFQ and is not a pure NASA product?

The NASA Authorization Act of 2010 specified the use of existing contractors for SLS and Orion.

But not every subcontractor. Was any attempt made by LM to sub-contract or license PICA-X from SpaceX? I sincerely doubt it.

[baldusi]

PICA-X is Spacex propriety material and is not available

Did NASA tried to request SpaceX to be the heatshield subcontractor for Orion and they flat denied or they have simply not made the RFQ and is not a pure NASA product?

The NASA Authorization Act of 2010 specified the use of existing contractors for SLS and Orion.

But not every subcontractor. Was any attempt made by LM to sub-contract or license PICA-X from SpaceX? I sincerely doubt it.

I think that currently PICA-X is the most proven non-ceramic/CCM heat shield material made in the US. When they decided to change to tiled, I don't see how the law would interfere.

[Dante80]

Is there anything wrong with Avcoat when used in tiles? Why would NASA want to change to PICA anyway?

[Lars-J]

Is there anything wrong with Avcoat when used in tiles? Why wound NASA want to change to PICA anyway?

Cost. Primarily because it is very labor intensive to hand-inject every cell in the honeycomb.