SpaceX COTS Demo 1 Updates

[Comga]

Sweet, the first COTS demo 1 Dragon image from the article: http://images.spaceref.com/news/2010/IMG_8390_KenKremer.jpg
(Interesting Draco covers, perhaps temporary until launch)

The shielding of the shroud lines for the parachutes appears quite different than on the drop-test Dragon.  I was wondering what they would do to make those sharp edge protrusions compatible with the supersonic portions of the launch.  It seems they have dramatically reduce the profiles.

I still wonder why SpaceX is putting so much effort into recovering this first operational Dragon.  It's not mandatory for COTS or CRS.

And perhaps those covers on the Draco's aren't "remove before flight" types.  I don't see any red tags or other indicators that they are non-flight.


(Now you can all go back to debating the wisdom of a static fire  )

[Lars_J]

I still wonder why SpaceX is putting so much effort into recovering this first operational Dragon.  It's not mandatory for COTS or CRS.

But it is. Dragon is supposed to provide down-mass capability - and you can't do that without recovering the capsule, can you? And the want to test as much as they can in this flight.

[mmeijeri]

There are multiple sensor inputs and actuator outputs to each engine.
Why would you run all those lines back to the LV guidance computer?

No special reason, just wondering why they split the software up that way. If you're using engines made by someone else then that's logical enough, but if it's all in-house, why not run it on a single (or redundant...) flight computer? I'm not saying they should, just curious about the reasons why they don't. Would there be any advantage if you could move the processor away from the heat and vibration of the engines?

[ugordan]

Would there be any advantage if you could move the processor away from the heat and vibration of the engines?

And greatly complicate the cabling for all sensors, valves to run all the way through to the top of the vehicle? It's a better defined and more manageable unit. There's a good reason it was done this way. Guidance software and engine control software are different beasts anyway as Jim said, so I'm not sure what merging them into a single place would accomplish.

Instead of a centralized ethernet interface they now have toward the flight computer you would need to convert each separate analog electrical sensor outputs to digital ethernet frames before sending them to the flight computer. Sending analog signals over 50 meters of cabling will mess A/D conversion there due to resistance losses, parasitic inductance, capacitance etc. Once you have a A/D converter for the sensors right in the engine and a box to pack that into an ethernet frame, you have yourself a... wait for it... engine controller.

[corrodedNut]

The shielding of the shroud lines for the parachutes appears quite different than on the drop-test Dragon.  I was wondering what they would do to make those sharp edge protrusions compatible with the supersonic portions of the launch.  It seems they have dramatically reduce the profiles.

The Dragon drop test article was missing most of its backshell TPS for that test. Only the areas surrounding or over the drogue and main parachute riser troughs, mortar tubes and main 'chute compartment had any. In the latest picture, the rest of the backshell has been added, so it has a 'smoother' appearance. Also, only two pieces (developmental?) of the heatshield were attached, one edge/lip piece bordering the main 'chute compartment, and another directly opposite on the (splashdown) leading edge.

From the available SpaceX literature, the backshell TPS is made of or partially made of a material called Acusil 2. I've tried to search and find out more about this material, but I haven't had much luck. It is a thermal insulator that appears to have a stiff, brittle, foam like consistency. It's a little hard to tell from the video, it seems as if the drogue risers rip right through it on deployment, like pulling the string on a bag of dog food.

If anyone knows more about, or has worked with this material, I'd appreciate any info.

[AnalogMan]

From the available SpaceX literature, the backshell TPS is made of or partially made of a material called Acusil 2. [...]

If anyone knows more about, or has worked with this material, I'd appreciate any info.

A search turned up the following info about the Acusil II material:

European Patent Application: EP2141070 Thermal barrier system
Publication date Jan 6, 2010
Assignee: ITT Manufacturing Enterprises, Inc

"[...] An example material for use in constructing the panels of the barrier system is a silicone material, such as a silicone syntactic foam material. A preferred silicone syntactic foam material that is used to form the panels of the thermal barrier system is commercially available under the trademark ACUSIL or ACUSIL II (ITT Corporation, New York).

The silicone syntactic foam material comprises a matrix of hollow silicone structures, e.g., microspheres, that are combined and/or fused together. The syntactic foam structure provides a low density, lightweight characteristic for the material while having a low thermal conductivity due to the physical nature of the silicone material and also the air content within the microsphere structures. A suitable silicone syntactic foam material (e.g., an ACUSIL material) can be selected so as to have a thermal conductivity within the range from about 0.050 - 0.055 W/(m*K) (e.g., about 0.053 W/(m*K)) and a density from about 15 lb/ft³ (about 240 kg/m³ ) to about 17 lb/ft³ (about 272 kg/m³ ). In addition, in an example embodiment the microspheres within the syntactic foam material are in the range from about 55 micrometers (microns) to about 70 microns."

http://www.freepatentsonline.com/EP2141070.html

This paper from LaRC/Ames also has some information about this material:

Aerothermodynamic Design of the Mars Science Laboratory Backshell and Parachute Cone

"ITT-Aerotherm's Acusil II is a silicone foam material that was chosen to protect the BIP and PCC because it permits radio frequency transmission and can be molded to cover complex surface geometries; the material is frequently used for tactical missile applications. There are multiple antennas inside the PCC that must be able to transmit signals before the PCC is ejected at supersonic parachute deployment. Variable Acusil II thicknesses were tailored to the design environments presented here in order to maintain acceptable bondline temperatures for various elements.⁶ Acusil II does not ablate for heat fluxes below 100 W/cm², which is well above what MSL will experience."

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090024230_2009023822.pdf

Hope this is of interest.

[yg1968]

Here is a link to a Spaceref.com article that includes the first picture of the Dragon cargo capsule along with some pictures of the 2nd Falcon 9.

http://www.spaceref.com/news/viewnews.html?id=1438

The goal of the static firing is to test launch pad propellant and pneumatic systems as well as the ground and flight control software that controls pad and launch vehicle configurations and assure that all systems are "GO" in expectation of a launch.

[mr. mark]

Comga - "still wonder why SpaceX is putting so much effort into recovering this first operational Dragon.  It's not mandatory for COTS or CRS. And perhaps those covers on the Draco's aren't "remove before flight" types.  I don't see any red tags or other indicators that they are non-flight".

Don't call me an expert but, if you are going to do a thuster test in flight, you probably need to remove the caps before launch.   

[ugordan]

Don't call me an expert but, if you are going to do a thuster test in flight, you probably need to remove the caps before launch.   

Yeah, I guess it's too late for that now... 

[mr. mark]

How strong is Spacex's assembly building at the cape? It now houses the Dragon capsule and Falcon 9. How would it hold up against hurricane force winds?

[Lars_J]

How strong is Spacex's assembly building at the cape? It now houses the Dragon capsule and Falcon 9. How would it hold up against hurricane force winds?

According to this news story: http://www.floridatoday.com/content/blogs/space/2009/01/falcon-9-up-then-down-at-lc-40.shtml

"The Falcon 9 can be raised and lowered quickly, so the company's hurricane plan is to lower the rocket and roll it into the hangar if a storm approaches. The hangar is built to withstand winds up to 135 mph."

[kevin-rf]

"The Falcon 9 can be raised and lowered quickly, so the company's hurricane plan is to lower the rocket and roll it into the hangar if a storm approaches. The hangar is built to withstand winds up to 135 mph."

A Category 3 direct hit, Category 4 is winds of 131mph to 155mph, but would it survive the storm surge from something that large? Me thinks a hurricane that large would float the whole kit and caboodle out to sea.

[corrodedNut]

Hope this is of interest.

Yes it is, thank you.

You did better than I did, I couldn't even find the manufacturer. Most of my searches came up with:
"Cure your diabetes and bursitis with ACUSIL 2!!" 

Now I'd like to know if there is a generic name for this stuff; it seems to be used on many re-entry vehicles.

[corrodedNut]

Don't call me an expert but,   

....must....resist...(gasping).....urge......to....snark....(death rattle)....

[Comga]

Comga - "And perhaps those covers on the Draco's aren't "remove before flight" types.  I don't see any red tags or other indicators that they are non-flight".

Don't call me an expert but, if you are going to do a thuster test in flight, you probably need to remove the caps before launch.   

Your wish is granted.  I won't call you an expert.

The question may be rephrased as why color the covers white to match the vehicle if you want them to stand out for visible indication that they have been removed?  One would think they would stencil in bright letters "NOT READY FOR FLIGHT" if they needed to be removed.  Normally you put a big red tag on things like that but perhaps they don't want tags flapping during the static firing.

There are other ways to open covers than to have them removed by hand.  They could pop off.   They could be actuated doors, which would also prevent being flooded with seawater after landing and exposure to airflow during reentry, although I have no knowledge if that or any other method is practical for these locations and criticality.  I am not suggesting they do anything, as no one cares or should care what I think SHOULD happen.  I am just asking a question about why things appear as they do.  We have smart people here who know things like this.

[Comga]

I still wonder why SpaceX is putting so much effort into recovering this first operational Dragon.  It's not mandatory for COTS or CRS.

But it is. Dragon is supposed to provide down-mass capability - and you can't do that without recovering the capsule, can you? And the want to test as much as they can in this flight.

Does the CRS contract include downmass?  I know that is a SpaceX goal, and a quite reasonable one for their long term plans, but is it part of CRS or COTS for which they are being paid?

[corrodedNut]

The question may be rephrased as why color the covers white to match the vehicle if you want them to stand out for visible indication that they have been removed?  One would think they would stencil in bright letters "NOT READY FOR FLIGHT" if they needed to be removed.  Normally you put a big red tag on things like that but perhaps they don't want tags flapping during the static firing.

There are other ways to open covers than to have them removed by hand.  They could pop off.   They could be actuated doors, which would also prevent being flooded with seawater after landing and exposure to airflow during reentry, although I have no knowledge if that or any other method is practical for these locations and criticality.  I am not suggesting they do anything, as no one cares or should care what I think SHOULD happen.  I am just asking a question about why things appear as they do.  We have smart people here who know things like this.

I think you're right, in that we shouldn't assume that they will be removed before flight.

In an earlier SpaceX update, from before F9 flight1, SpaceX was preparing the Dragon qual unit with "test Draco thruster housings", presumably to gather aerodynamic data in flight. These were later deleted from the final Dragon flight article. So, that might be a hint as to whether or not these covers are removed before flight or not.

To compare, and unless I'm mistaken, shuttle RCS tyvek covers are designed to 'blow-off' after lift off.

[yg1968]

I still wonder why SpaceX is putting so much effort into recovering this first operational Dragon.  It's not mandatory for COTS or CRS.

But it is. Dragon is supposed to provide down-mass capability - and you can't do that without recovering the capsule, can you? And the want to test as much as they can in this flight.

Does the CRS contract include downmass?  I know that is a SpaceX goal, and a quite reasonable one for their long term plans, but is it part of CRS or COTS for which they are being paid?

Cargo return downmass is an option under the SpaceX CRS contract (see page 5 of the document -which is page 7 of the PDF, see also the index on page 1 -which is page 3 of the PDF):

http://www.nasa.gov/centers/johnson/pdf/418857main_sec_nnj09ga04b.pdf

[Lars_J]

That PDF does not seem to be the document you are referring to. Or perhaps I am confused.

(see page 5 of the document -which is page 7 of the PDF, see also the index on page 1 -which is page 3 of the PDF)

Wow... that has to be the most byzantine page reference into a PDF document I have seen - I certainly canot make sense of it  
EDIT: Ok I think I found it. But it is still not very conclusive, since the document is lacking context.

[cheesybagel]

Another thing that can happen is different launch environments in Texas and Florida. Just because something works in the Texas test stand, it does not mean it will work in the Florida launch site. There were plenty of occurrences of issues like this during the static test firing campaign for the first Falcon 9.

wrong, that is bad logic and would mean that spacex has bad engineering.

Because something works in the Texas test stand, it does mean it will work in the Florida launch site.
That is the reason for the test stand in TX, otherwise eliminate the stand in TX and use FL for everything.

+19 EELVs with only 1 pad test firings
+100 Delta II's with none

WDR's with off pad testing does everything necessary

The Texas site provides a way to test the stages separately. Lack of proper separate testing (including static testing) for each stage was a problem with e.g. the Europa launcher. Even with the N-1 there were many quality control and design issues which were only found and corrected too late in the process because they had no test stand, or static testing.

Texas is also a heck of a lot closer to California than Florida.

Problems happen. Thinking that you can solve all engineering problems by adding multiple layers of paperwork, fault trees, probabilistic risk assessments, check lists, and the like, well... The truth is these techniques do not work well when the vehicles are evolving continuously. Also, you cannot add a check for an unknown problem.

Delta II's usually have solids. You cannot do hot fire tests with solids. Even most EELV launches I can remember had some solids.