SpaceX COTS Demo 2/3 Updates (THREAD 2)

[marsman2020]

Combining COTS2/3 is a significant financial advantage to SpaceX (get paid on two large milestones with only 1 launch vehicle and spacecraft) so I don't think anything will un-combine them short of an in-flight issue during the COTS2 portion preventing the COTS3 portion from happening.

Of course the taxpayers get 1/2 the flight data that was associated with those 2 milestones, but who cares about that.

[Comga]

Isn't white more reflective across the spectrum? I remember they painted the Apollo CMs white on one side for Skylab extended exposure to have better thermal control than the usual silver coating.

It's probably also more than just what one sees in the optical range, IR may be more important here and maybe that's where TiO2 excels.

Correct. White paint can have higher emissivity, the ability to radiate heat, than metalic surfaces.  Thermal cryo-radiators are often painted white to reflect accidentally impinging sunlight.

However, wasn't the capsule off-white blankets to begin with?

My guess, and it is only a guess, is that NASA was unhappy with the margins on the thermal analysis. I doubt that SpaceX  just started modeling.   

[Jim]

My guess, and it is only a guess, is that NASA was unhappy with the margins on the thermal analysis. I doubt that SpaceX  just started modeling.   

I would say it is Spacex that is not happy with it, NASA has no real say on Dragon internal system temps.  But if it is heating up the pressurized compartment then yes, NASA has a say

[ugordan]

Combining COTS2/3 is a significant financial advantage to SpaceX (get paid on two large milestones with only 1 launch vehicle and spacecraft)

They aren't large. The savings come from not launching two vehicles, not COTS money.

Of course the taxpayers get 1/2 the flight data that was associated with those 2 milestones, but who cares about that.

Good thing they don't care about that, otherwise they'd like Orbital's COTS profile even less.

[yg1968]

"The #SpaceX Dragon has to get a new paint job to address thermal issue for #ISS docking ... one reason for delay."

https://twitter.com/#/b0yle/status/165176988846395393

Interesting.

And people think that building a spacecraft is easy. Anyhoo...

The way I read this morning's Florida Today article is that the thermal issue is with keeping the propellant tanks happy.

Space is hard, but finding a basic thermal issue like this at this point in the game is a little disheartening.  The only mitigating circumstance is if something changed from NASA, like shadowing or ISS attitude or something.

See this link:

http://www.floridatoday.com/article/20120202/SPACE/120202025/NASA-sets-new-targets-Soyuz-SpaceX-launches?odyssey=tab|topnews|text|Space

Suffredini said SpaceX is closing out a range of technical issues with its Dragon spacecraft, including electromagnetic interference, propellant tank insulation, engine delamination and software adjustments.

Once scheduled to launch Feb. 7 and now tentatively targeting a March 20 launch from Cape Canaveral, Suffredini said the first week of April is a realistic target for launch of the unmanned Dragon atop a Falcon 9 rocket.

[corrodedNut]

Suffredini said SpaceX is closing out a range of technical issues with its Dragon spacecraft, including electromagnetic interference, propellant tank insulation, engine delamination and software adjustments.
 

What do they mean by "engine delamination"?

[cuddihy]

Suffredini said SpaceX is closing out a range of technical issues with its Dragon spacecraft, including electromagnetic interference, propellant tank insulation, engine delamination and software adjustments.
 

What do they mean by "engine delamination"?

My guess -- Draco nozzle issue with long-term exposure to hard vacuum that didn't exhibit on COTS-1 due to the short time involved. Any takers?

[Prober]

Combining COTS2/3 is a significant financial advantage to SpaceX (get paid on two large milestones with only 1 launch vehicle and spacecraft) so I don't think anything will un-combine them short of an in-flight issue during the COTS2 portion preventing the COTS3 portion from happening.

Of course the taxpayers get 1/2 the flight data that was associated with those 2 milestones, but who cares about that.

Well let's face the facts, this has not saved money, or given us a working system in less time.   Someone in charge needs to make this call, and get it done.

Look what happened with Orbital, they had a flight test was added.  Should SpaceX be treated any different?

Edit: info upgraded

[pippin]

Isn't white more reflective across the spectrum? I remember they painted the Apollo CMs white on one side for Skylab extended exposure to have better thermal control than the usual silver coating.

It's probably also more than just what one sees in the optical range, IR may be more important here and maybe that's where TiO2 excels.

Correct. White paint can have higher emissivity, the ability to radiate heat, than metalic surfaces.

Um... but that's the opposite of reflectivity.
BLACK materials (in the physical sense of "black") are emissive while "white" materials are reflective.
You can't have a highly reflective material that's also emissive, you have to pick what you need.
If you need to radiate excess heat you have to live with the fact that the material also will heat up upon exposure to the sun.
If you want reflective to not heat up you can't radiate away energy, at least not in the same wavelength.

The one thing you can do is reflect visible spectrum and emit in IR but then you also heat up in the IR range.
[/quote]

[mr. mark]

The bottom line is that if everything goes correctly in a little over 2 months Spacex will have a working cargo system. That's far ahead of Orbital that has not even launch Antares yet. Spacex has launched 2 falcon 9's already.

[ugordan]

Look what happened with Orbital, they had engine issues and a flight test was added.

Risk reduction flight was added *before* engine issues...

[dunderwood]

Well let's face the facts, this has not saved money, or given us a working system in less time.   Someone in charge needs to make this call, and get it done.

Look what happened with Orbital, they had engine issues and a flight test was added.  Should SpaceX be treated any different?

SpaceX already paid for a flight test of the launcher.  Adding a COTS 3 doesn't mean COTS 2 would have happened any sooner. 

[Prober]

Look what happened with Orbital, they had engine issues and a flight test was added.

Risk reduction flight was added *before* engine issues...

thx, corrected

[Prober]

Well let's face the facts, this has not saved money, or given us a working system in less time.   Someone in charge needs to make this call, and get it done.

Look what happened with Orbital, they had engine issues and a flight test was added.  Should SpaceX be treated any different?

SpaceX already paid for a flight test of the launcher.  Adding a COTS 3 doesn't mean COTS 2 would have happened any sooner. 

One successful flight in 2010 doesn't a system make.  The history shows that had the COTS2 gone as planned, SpaceX would have had more "real" flight data than they have to show now.

[SpacexULA]

One successful flight in 2010 doesn't a system make.  The history shows that had the COTS2 gone as planned, SpaceX would have had more "real" flight data than they have to show now.

Some of these issues would have had to been resolved for even a COTS2 mission to go off.  If it was COTS2 instead of COTS2/3 we likely would still be in a delay.

[apace]

One successful flight in 2010 doesn't a system make.  The history shows that had the COTS2 gone as planned, SpaceX would have had more "real" flight data than they have to show now.

As it shows now, any COTS2 flight alone will not be launched much earlier than the combined mission. To much work has to be done between COTS1 and 2.

[HMXHMX]

Suffredini said SpaceX is closing out a range of technical issues with its Dragon spacecraft, including electromagnetic interference, propellant tank insulation, engine delamination and software adjustments.
 

What do they mean by "engine delamination"?

My guess -- Draco nozzle issue with long-term exposure to hard vacuum that didn't exhibit on COTS-1 due to the short time involved. Any takers?

The Draco engine is all metal.  Not sure what this means, unless it is grabbled and refers to spallation of silicide-like coatings or equivalent on the refractory metal nozzle.

[Comga]

Isn't white more reflective across the spectrum? I remember they painted the Apollo CMs white on one side for Skylab extended exposure to have better thermal control than the usual silver coating.

It's probably also more than just what one sees in the optical range, IR may be more important here and maybe that's where TiO2 excels.

Correct. White paint can have higher emissivity, the ability to radiate heat, than metalic surfaces.

Um... but that's the opposite of reflectivity.
BLACK materials (in the physical sense of "black") are emissive while "white" materials are reflective.
You can't have a highly reflective material that's also emissive, you have to pick what you need.
If you need to radiate excess heat you have to live with the fact that the material also will heat up upon exposure to the sun.
If you want reflective to not heat up you can't radiate away energy, at least not in the same wavelength.

The one thing you can do is reflect visible spectrum and emit in IR but then you also heat up in the IR range.

You might think that, your first point, but you would be wrong.  Your last point better describes the actual conditions. 

You would guess that black paint would be more emissive than white, but black and white are just what your eye sees.  If you look through an IR viewer, black masking tape is indistinguishable from white, because it is made black with dye.   How they behave in a radiative fashion, has to be determined by measurements of infrared properties. 

Emissivity, absorbtivity, and reflectivity are only constrained to each other locally, at specific wavelenths.  They can vary spectrally and not violate the Third Law of Thermodynamics.

Using only the quote above about needing to insulate the propellant tanks, and the statement about paint, SpaceX might be installing metalic shell sections or something else to decrease the emissivity in the thermal IR, out beyond 10 microns wavelength, or blackening the areas to absorb more sunlight.  It is not clear how to do either of these things on finished exterior blankets like we saw from the DC display of the returned Dragon capsule.

[Comga]

Well let's face the facts, this has not saved money, or given us a working system in less time.   Someone in charge needs to make this call, and get it done.

Look what happened with Orbital, they had engine issues and a flight test was added.  Should SpaceX be treated any different?

SpaceX already paid for a flight test of the launcher.  Adding a COTS 3 doesn't mean COTS 2 would have happened any sooner. 

One successful flight in 2010 doesn't a system make.  The history shows that had the COTS2 gone as planned, SpaceX would have had more "real" flight data than they have to show now.

Flying COTS-2 still required a cleared approach to the ISS with trained operators on board.  It may also have required that the SSARMS software be updated.  It is not clear that these conditions could have been met earlier, or even now.  It sounds like a issues discovered in a joint development process.  Neither party can get that far ahead of the other. 

This is so much better than NASA writing arbitrary specifications, even ones that are supposed to capture fifty years or spaceflight experience.  (Oh has this been painful for me.) If that means a couple of last minute delays, so be it.

[pippin]

You would guess that black paint would be more emissive than white, but black and white are just what your eye sees.

That's why I said "in the physical sense" where a "black" body is one that emits and absorbs a lot of radiation in the range you are testing for.

That's also why I originally referred specifically to TiO2 because TiO2 has a high reflectivity in visible as well as infrared wavelengths.