Author Topic: Transpiration Cooling?  (Read 29583 times)

Offline Proponent

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Transpiration Cooling?
« on: 01/28/2019 06:31 pm »
What, broadly speaking, is the TRL of re-entry transpiration cooling?

Did any of the USAF's boost-glide re-entry vehicles of the 1960's--ASSET (Aerothermodynamic Elastic Structural Systems Environmental Tests) or PRIME (Precision Recovery Including Maneuvering Entry), or BGRV (Boost Glide Re-entry Vehicle) flights--test it?

Offline Jim

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Re: Transpiration Cooling?
« Reply #1 on: 01/28/2019 06:37 pm »


Did any of the USAF's boost-glide re-entry vehicles of the 1960's--ASSET (Aerothermodynamic Elastic Structural Systems Environmental Tests) or PRIME (Precision Recovery Including Maneuvering Entry), or BGRV (Boost Glide Re-entry Vehicle) flights--test it?

no

Offline vaporcobra

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Re: Transpiration Cooling?
« Reply #2 on: 01/28/2019 07:28 pm »
What, broadly speaking, is the TRL of re-entry transpiration cooling?

Did any of the USAF's boost-glide re-entry vehicles of the 1960's--ASSET (Aerothermodynamic Elastic Structural Systems Environmental Tests) or PRIME (Precision Recovery Including Maneuvering Entry), or BGRV (Boost Glide Re-entry Vehicle) flights--test it?

Fairly certain it's never been flight-tested. As far as I can tell, the best research yet done was by DLR in support of their SpaceLiner program in the 2000s, they did some coupon testing at an arc jet facility and gathered some solid data. Attached my favorite papers from a few-hour search.

Edit: Donosauro found a source indicating that transpiration cooling has been tested during actual reentries.

Edit 2: Orbital reentry testing was misread, only flight-testing done thus far was on a suborbital sounding rocket launch called SHEFEX II.
https://arc.aiaa.org/doi/10.2514/6.2014-2676

Edit 3: SHEFEX II launched in 2012 and was reportedly quite successful. SHEFEX III would be a veritable goldmine of data for transpiration cooling and was supposed to follow it, but it's hard to tell if DLR still has plans for the follow-on.
« Last Edit: 01/28/2019 09:43 pm by vaporcobra »

Offline Lar

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Re: Transpiration Cooling?
« Reply #3 on: 01/28/2019 07:34 pm »
Everyone else probably already knows what coupon testing is.. I didn't

https://www.quora.com/What-is-a-coupon-in-steel-coupon-testing-for-a-tensile-strength-test

A coupon is a small sample of the material of interest that can be easily tested. Different coupons may bet tested in a wide variety of ways, for far less cost than testing the actual article the material is used to fabricate would cost.

Interesting that 3 of the four papers found had van Foreest as an author or coauthor. Sounds like that is the person to talk to?
« Last Edit: 01/28/2019 07:35 pm by Lar »
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Offline Llian Rhydderch

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Re: Transpiration Cooling?
« Reply #4 on: 01/28/2019 07:45 pm »
Looks like we'll need to dispatch the L2 welcoming committee with an invitation to van Foreest, using the space industry professional VIP program.   ;D
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Offline Proponent

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Re: Transpiration Cooling?
« Reply #5 on: 01/28/2019 09:11 pm »
Could we say the TRL is about 3?

Offline Donosauro

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Re: Transpiration Cooling?
« Reply #6 on: 01/28/2019 09:22 pm »
This link mentions a number of flight experiments:
https://www.sto.nato.int/publications/STO%20Educational%20Notes/STO-EN-AVT-261/EN-AVT-261-05.pdf

It mentions testing "...during real re-entry flight, such as in the FOTON 9, EXPRESS, FOTON-M2, and SHEFEX missions."

Offline vaporcobra

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Re: Transpiration Cooling?
« Reply #7 on: 01/28/2019 09:37 pm »
This link mentions a number of flight experiments:
https://www.sto.nato.int/publications/STO%20Educational%20Notes/STO-EN-AVT-261/EN-AVT-261-05.pdf

It mentions testing "...during real re-entry flight, such as in the FOTON 9, EXPRESS, FOTON-M2, and SHEFEX missions."

Ah, that was a slight mis-read but you are still technically correct. I think the author meant that DLR's custom "C/C-SiC" TPS was flight-tested on the above missions, while transpiration cooling has been tested once in flight on the suborbital SHEFEX II mission. Lots more reading to do, now :D

https://www.dlr.de/dlr/en/desktopdefault.aspx/tabid-10664/1151_read-4614/#/gallery/6918
https://arc.aiaa.org/doi/10.2514/6.2014-2676

Edit: SHEFEX III's launch is NET 2021 on a Brazilian rocket that hasn't launched yet :( Also attached the results paper from the transpiration experiment on SHEFEX II.
« Last Edit: 01/28/2019 10:13 pm by vaporcobra »

Online envy887

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Re: Transpiration Cooling?
« Reply #8 on: 01/28/2019 09:56 pm »
Do we know if the water cooling on F9 B5 suborbital entries is transpiration, or something else like spray or recirculation?

Online rakaydos

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Re: Transpiration Cooling?
« Reply #9 on: 01/29/2019 01:00 pm »
I feel the details of the transpiration cooling system are heavily dependant on the abilityof the stainless hull to minimize radiative heating.

Since no one in the engineering thread seems willing to calculate it, what tools do I need to figure out just the radiative heating from reentry, and 310 stainless's reflectivity?

Online envy887

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Re: Transpiration Cooling?
« Reply #10 on: 01/29/2019 01:45 pm »
I feel the details of the transpiration cooling system are heavily dependant on the abilityof the stainless hull to minimize radiative heating.

Since no one in the engineering thread seems willing to calculate it, what tools do I need to figure out just the radiative heating from reentry, and 310 stainless's reflectivity?

It's a rather complex problem to solve even in a single dimension, since most of the properties you need to calculate temperature are functions of temperature. Stainless, for example, doesn't really reflect IR at all if it is operating at 1000 C. Also, convective heating is relevant, so focusing on radiative transfer will give the wrong answer.

Offline meekGee

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Re: Transpiration Cooling?
« Reply #11 on: 01/29/2019 01:53 pm »
I feel the details of the transpiration cooling system are heavily dependant on the abilityof the stainless hull to minimize radiative heating.

Since no one in the engineering thread seems willing to calculate it, what tools do I need to figure out just the radiative heating from reentry, and 310 stainless's reflectivity?
More like "unable"... This is almost as complex as the combustion chamber calcs.

Really world-class problem, something maybe only SpaceX can solve.
« Last Edit: 01/29/2019 02:23 pm by meekGee »
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Online rakaydos

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Re: Transpiration Cooling?
« Reply #12 on: 01/29/2019 02:08 pm »
I feel the details of the transpiration cooling system are heavily dependant on the abilityof the stainless hull to minimize radiative heating.

Since no one in the engineering thread seems willing to calculate it, what tools do I need to figure out just the radiative heating from reentry, and 310 stainless's reflectivity?

It's a rather complex problem to solve even in a single dimension, since most of the properties you need to calculate temperature are functions of temperature. Stainless, for example, doesn't really reflect IR at all if it is operating at 1000 C. Also, convective heating is relevant, so focusing on radiative transfer will give the wrong answer.
I am, for the moment, handwaving all convection heating as managed by the transpiration cooling system, to allow a first order calculation.

If the properties of heating vary over time, then time is something we need to include.

Assuming the hull starts at cryogenic methane temps. How far into entry would the steel hull be when the reflective properties changed, from radiative heating alone? (That's, what, when it reaches500 degrees C?)

What are stainless steel properties after that temperature?

I feel this is solvable  given the hanwaves I am using, and the answer defines the problem this thread is about.

Online Semmel

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Re: Transpiration Cooling?
« Reply #13 on: 01/29/2019 02:24 pm »
Wikipedia has a nice article on atmospheric entry, it doesnt provide you with answers but it gives you a good overview of the complexity: https://en.wikipedia.org/wiki/Atmospheric_entry

TL;DR:The complexity comes from the fact that you cant simplify the problem without making huge errors.

Offline aameise9

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Re: Transpiration Cooling?
« Reply #14 on: 01/29/2019 02:55 pm »
Well, Wikipedia does give a formula for radiative heat transfer, which simplifies to the attached for two parallel surfaces (view angle = 1).

Given the respective emissivities of reentry plasma and of stainless steel, this may provide an order of magnitude.


Offline Eric Hedman

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Re: Transpiration Cooling?
« Reply #15 on: 01/29/2019 02:57 pm »
Is this the biggest technology risk in the development of Starship?

Online acsawdey

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Re: Transpiration Cooling?
« Reply #16 on: 01/29/2019 03:17 pm »
This seems like a very good reason to build the second prototype so that they can instrument the skin and slowly work their way up to re-entry conditions, rather than trying to solve this extremely hard problem of theoretically calculating the heat load.

One other thing that hasn't been mentioned -- methane has some strong absorption bands in the IR (after all it's a greenhouse gas). So the film layer of methane from the transpiration cooling is going to absorb some of the incoming IR and transport the heat away.

Online envy887

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Re: Transpiration Cooling?
« Reply #17 on: 01/29/2019 03:34 pm »
Is this the biggest technology risk in the development of Starship?

Yes, IMO. TPS reuse was always the biggest risk, along with composite structures. Stainless with transpiration greatly reduces the structures risk, but somewhat increases the TPS risk.

Online envy887

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Re: Transpiration Cooling?
« Reply #18 on: 01/29/2019 03:36 pm »
This seems like a very good reason to build the second prototype so that they can instrument the skin and slowly work their way up to re-entry conditions, rather than trying to solve this extremely hard problem of theoretically calculating the heat load.

One other thing that hasn't been mentioned -- methane has some strong absorption bands in the IR (after all it's a greenhouse gas). So the film layer of methane from the transpiration cooling is going to absorb some of the incoming IR and transport the heat away.

They can also simply trade payload mass for coolant mass initially, as long as the coolant pumping system has some margin for higher than expected flowrates. Start extra cold, then optimize for coolant mass.

Online acsawdey

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Re: Transpiration Cooling?
« Reply #19 on: 01/29/2019 03:44 pm »
This seems like a very good reason to build the second prototype so that they can instrument the skin and slowly work their way up to re-entry conditions, rather than trying to solve this extremely hard problem of theoretically calculating the heat load.

One other thing that hasn't been mentioned -- methane has some strong absorption bands in the IR (after all it's a greenhouse gas). So the film layer of methane from the transpiration cooling is going to absorb some of the incoming IR and transport the heat away.

They can also simply trade payload mass for coolant mass initially, as long as the coolant pumping system has some margin for higher than expected flowrates. Start extra cold, then optimize for coolant mass.

Precisely, it's incremental testing just like F9 re-entry has been.

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