Starship heat shield

[TomH]

Starship heatshield - Bathroom Tiles - Dragon Scales - Carbon Fibre Fur Coat or something else?......What do you reckon?

Tiles and scales, when damaged, require localized work. Any liquid or gel application requires either localized repair or extensive debonding. It would be good to have something like a one time use disposable jacket/sleeve/glove that goes on/comes off quickly and easily, but with multiple secure attachment points or lines. An actual jacket that humans wear is usually secured with a zipper which is faster and more secure than buttons. I am not calling for an actual zipper system, but merely using that as an analogy for a system that is fast and secure. Even if you wind up throwing something away after every flight, if the amount of man and machine hours were greatly reduced, it could be far less expensive. A serious long pole would be added mass. The system would require something that is lightweight, resistant to the heat and abrasion, can be held securely durning launch and entry, yet can quickly and easily be attached and detached when required.

[Eric Hedman]

Considering all the heat shield challenges from returning from LEO, I have to wonder how they are going to be able to handle the return speed from the Moon or Mars.  Dragon handles entry temperatures of around 3400 degrees Fahrenheit.  Apollo had to deal with around 5000 degrees.  Improving the heat shield to handle another 1600 degrees doesn't seem trivial to me.

[Blackhorse]

With Starship being a propellant rich architecture, how about propulsive braking: to lower the reentry velocity from interplanetary (11.2 km/s) to classic LEO (7.8 km/s) ?

[pjm1]

With Starship being a propellant rich architecture, how about propulsive braking: to lower the reentry velocity from interplanetary (11.2 km/s) to classic LEO (7.8 km/s) ?

Because of the rocket equation, there is no such thing as a "propellant rich architecture" when ISPs are < 1000 (and probably more like < 5000).  The "cost" of aerobraking is mass and reusability... and the first is so massively (literally!) offset by the additional mass of fuel to do the same propulsively.

[Kazioo]

Considering all the heat shield challenges from returning from LEO, I have to wonder how they are going to be able to handle the return speed from the Moon or Mars.  Dragon handles entry temperatures of around 3400 degrees Fahrenheit.  Apollo had to deal with around 5000 degrees.  Improving the heat shield to handle another 1600 degrees doesn't seem trivial to me.

The tiles should handle it and SpaceX knew that years ago thanks to lab tests like with the plasmajet etc. (they showed several test videos over the years).
But that's assuming the attachments and sealings work perfectly and currently they don't.

[catdlr]

This will be interesting! I'll highlight him and his journey in solid fuel rocketry on a different thread—he's entertaining and knowledgeable. Looking forward to sharing this and learning more from him! From the SpaceX Bakery.


BPS.space
@bps_space
Filming at the Bakery today 📸

https://twitter.com/bps_space/status/1982912863904903337

[TomH]

Considering all the heat shield challenges from returning from LEO, I have to wonder how they are going to be able to handle the return speed from the Moon or Mars.  Dragon handles entry temperatures of around 3400 degrees Fahrenheit.  Apollo had to deal with around 5000 degrees.  Improving the heat shield to handle another 1600 degrees doesn't seem trivial to me.

Capsules have a blunt entry face and a higher mass density. On Lunar return, Orion and Apollo have higher entry velocity than Dragon and other capsules returning only from LEO. STS and SS have a lower mass density as well as a much broader surface area over which to disperse the kinetic energy of EDL. Therefore, STS and SS experience lower EDL temperatures.

It should also be noted that, due to the complexities of hypersonic fluid (gas) dynamics, the bow shock wave experiences higher temperature than the actual surface of the spacecraft itself. I have read that CDF simulations indicate that the Stardust bow shock temperature reached a high of 50,000K at an altitude of 71km with temp dropping quickly to 10,000K at 50km. These ultra intense temperatures are in low density atmospheric molecules that are some distance in front of the solid/gas interface surface and they flow around the ship without touching it. The phenomena does not involve thermal conduction in the same manner as normal thermal conductive transfer through materials when there is no convective flow going around the ship. The surface of the TPS pushes a bow shock wave out in front of the ship and there is more friction between molecules at the front of the bow shock wave with other non-moving molecules that the bow-shock wave hits, as compared to the friction between the surface of the TPS and the air molecules it is encountering at the immediate surface of that TPS. That is a very generalized description. Shape of the entering surface (as well as the leeward side) and also the angle of attack are important variables as well. Often, the highest intensity is off on the farthest corners rather than the front center of the entering surface. I am no expert in this subject, but I do know enough to know that it is exceedingly complicated and to realize that my understanding of it is merely cursory.

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[Twark_Main]

isn’t there a better way to do entry, so that spacecraft can be reusable with less maintenance?

...

7) Other ideas?

How about geometry? A lenticular reentry vehicle has a large effective "radius" over most of its surface. Plus if you're using fancy TPS it can be concentrated only at the perimeter (which has a smaller effective radius), and then you benefit from cube-square scaling.

Effectively this is the "in the limit" implementation of the concept of enlarging the flaps for more drag and reduced peak heating...

See also https://ntrs.nasa.gov/api/citations/19850014055/downloads/19850014055.pdf

[Legios]

With Starship being a propellant rich architecture, how about propulsive braking: to lower the reentry velocity from interplanetary (11.2 km/s) to classic LEO (7.8 km/s) ?

Because of the rocket equation, there is no such thing as a "propellant rich architecture" when ISPs are < 1000 (and probably more like < 5000).  The "cost" of aerobraking is mass and reusability... and the first is so massively (literally!) offset by the additional mass of fuel to do the same propulsively.

It is propellant rich if you consider tanking.
If you ae willing to spend the resources, just have the return vehicle refuel before reentry. Have it rendezvous at the apogee of a HEO with a depot.

Probably crazy wasteful, but it could be done.

[rfdesigner]

With Starship being a propellant rich architecture, how about propulsive braking: to lower the reentry velocity from interplanetary (11.2 km/s) to classic LEO (7.8 km/s) ?

Because of the rocket equation, there is no such thing as a "propellant rich architecture" when ISPs are < 1000 (and probably more like < 5000).  The "cost" of aerobraking is mass and reusability... and the first is so massively (literally!) offset by the additional mass of fuel to do the same propulsively.

It is propellant rich if you consider tanking.
If you ae willing to spend the resources, just have the return vehicle refuel before reentry. Have it rendezvous at the apogee of a HEO with a depot.

Probably crazy wasteful, but it could be done.

To refuel you would have to rendezvous and that means achieving a matched orbit to the tanker, which means you need the fuel BEFORE rendezvous in order to achieve orbit.  Catch 22.

[Kazioo]

isn’t there a better way to do entry, so that spacecraft can be reusable with less maintenance?

...

7) Other ideas?

How about geometry?

Elon suggested similar idea several times, but he usually called it "dragon wings", so most people thought he was just making some jokes.

[Legios]

With Starship being a propellant rich architecture, how about propulsive braking: to lower the reentry velocity from interplanetary (11.2 km/s) to classic LEO (7.8 km/s) ?

Because of the rocket equation, there is no such thing as a "propellant rich architecture" when ISPs are < 1000 (and probably more like < 5000).  The "cost" of aerobraking is mass and reusability... and the first is so massively (literally!) offset by the additional mass of fuel to do the same propulsively.

It is propellant rich if you consider tanking.
If you ae willing to spend the resources, just have the return vehicle refuel before reentry. Have it rendezvous at the apogee of a HEO with a depot.

Probably crazy wasteful, but it could be done.

You could top off before leaving the moon or mars.  Use that fuel to enter a HEO, then have the tanker meet you at the apogee where rendezvous would use the least amount of delta-V.

It's been a long time since I've done any rocket math, so I'm sure it's crazy wasteful and inefficient.  But I'd bet possible.

[InterestedEngineer]

I was doing some research for how well the tiles will insulate from solar and earth shine, and ran across this oddity:

Do the tiles on Starship have 65x worse thermal conductivity than the Space Shuttle? 

all units are  (W/m-K)

Space Shuttle Tiles:  https://tpsx.arc.nasa.gov/MaterialProperty?id=1&property=4

.013 at 255K
.289 at 1533K

TUFI:  https://tpsx.arc.nasa.gov/MaterialProperty?id=8&property=3

.843 at 255K
1.6 at 1505K

I find it hard to believe the Starship tiles have 65x worse thermal conductivity than the Space shuttle tiles at cold-ish temperatures and 5.5x worse at 1500K?

Are we sure the TUFI (material #8) is really what's on the Starship?

[Twark_Main]

isn’t there a better way to do entry, so that spacecraft can be reusable with less maintenance?

...

7) Other ideas?

How about geometry?

Elon suggested similar idea several times, but he usually called it "dragon wings", so most people thought he was just making some jokes.

I always assumed the dragon wings was some sort of deployable structure. In a lenticular vehicle, the main structure itself provides that geometry.

Of course the whole trick is to make it lightweight. Otherwise you pay more in the structure than you save in the heat shield...

[volker2020]

I was doing some research for how well the tiles will insulate from solar and earth shine, and ran across this oddity:

Do the tiles on Starship have 65x worse thermal conductivity than the Space Shuttle? 

all units are  (W/m-K)

Space Shuttle Tiles:  https://tpsx.arc.nasa.gov/MaterialProperty?id=1&property=4

.013 at 255K
.289 at 1533K

TUFI:  https://tpsx.arc.nasa.gov/MaterialProperty?id=8&property=3

.843 at 255K
1.6 at 1505K

I find it hard to believe the Starship tiles have 65x worse thermal conductivity than the Space shuttle tiles at cold-ish temperatures and 5.5x worse at 1500K?

Are we sure the TUFI (material #8) is really what's on the Starship?

I would assume that the thermal conductivity of a material, that is mostly hollow, would vary greatly, whether it is located in an air / plasma filled environment or in a high vacuum. So I think it is a reasonable guess, that the k factor in space is much better. 

[InterestedEngineer]

I was doing some research for how well the tiles will insulate from solar and earth shine, and ran across this oddity:

Do the tiles on Starship have 65x worse thermal conductivity than the Space Shuttle? 

all units are  (W/m-K)

Space Shuttle Tiles:  https://tpsx.arc.nasa.gov/MaterialProperty?id=1&property=4

.013 at 255K
.289 at 1533K

TUFI:  https://tpsx.arc.nasa.gov/MaterialProperty?id=8&property=3

.843 at 255K
1.6 at 1505K

I find it hard to believe the Starship tiles have 65x worse thermal conductivity than the Space shuttle tiles at cold-ish temperatures and 5.5x worse at 1500K?

Are we sure the TUFI (material #8) is really what's on the Starship?

I would assume that the thermal conductivity of a material, that is mostly hollow, would vary greatly, whether it is located in an air / plasma filled environment or in a high vacuum. So I think it is a reasonable guess, that the k factor in space is much better.

I'm looking at the difference. I doubt the same NASA materials website would publish the same metric under different test conditions without providing notification.

[rsdavis9]

I was doing some research for how well the tiles will insulate from solar and earth shine, and ran across this oddity:

Do the tiles on Starship have 65x worse thermal conductivity than the Space Shuttle? 

all units are  (W/m-K)

Space Shuttle Tiles:  https://tpsx.arc.nasa.gov/MaterialProperty?id=1&property=4

.013 at 255K
.289 at 1533K

TUFI:  https://tpsx.arc.nasa.gov/MaterialProperty?id=8&property=3

.843 at 255K
1.6 at 1505K

I find it hard to believe the Starship tiles have 65x worse thermal conductivity than the Space shuttle tiles at cold-ish temperatures and 5.5x worse at 1500K?

Are we sure the TUFI (material #8) is really what's on the Starship?

I would assume that the thermal conductivity of a material, that is mostly hollow, would vary greatly, whether it is located in an air / plasma filled environment or in a high vacuum. So I think it is a reasonable guess, that the k factor in space is much better.

I'm looking at the difference. I doubt the same NASA materials website would publish the same metric under different test conditions without providing notification.

As a guess this is the heat conductivity for the fused layer versus the whole tile?

[rsdavis9]

A couple of questions:
1. Is the feeling of everyone here and at spacex that the pinning of tiles is the correct way to go? Will they eventually pin all the tiles? Obviously we need a L2 answer for spacex.

2. Has everybody seen this video that is very negative but gives good info on waterproofing materials?


It sounds like binding to the oxygen atoms at the outside of the silica is the method to waterproof. Right now they use methyl groups which I guess are not heat resistant.

How about SiC no oxygen in there to bind to water?

[JamesH65]

YouTube video titled "This...is sooo stupid" Vs SpaceX engineers who've been working on this for years.

Hmm, tough choice.

[Robotbeat]

Thunderf00t videos are not worth engaging with.