Jump to content

What If Starship's Hull Was.... Tungsten or a Tungsten Alloy?


Spacescifi
 Share

Recommended Posts

I mean apparently a heat shield is a big issue and Starship MUST be reusuable so tungsten or at least a tungsten alloy may be a good idea.

 

Somebody may scream something about the cost, but lets forget about cost for a moment.

What choices are ought there that I am thinking of?

 

1. Tungsten/steel alloy.

2. Tungsten/titanium alloy.

3. Tungsten/alluminum alloy.

 

I have no idea how well these alloys would perform for starship.

 

Maybe tungsten would be worse for space radiation protection, or maybe it is so heavy you need a torchship to lift it in significant amounts.. and starship is not that.

 

 

 

Link to comment
Share on other sites

Tungsten has a cross-sectional ultimate tensile strength that is 90% greater than stainless steel. However, its density is 145% greater than stainless steel. So a tungsten tank with the equivalent strength of a steel tank will be around 30% heavier.

It's also very brittle and becomes more brittle as it gets cold, which makes it VERY poor for holding cryogens.

And before you suppose that a layer of tungsten will work: tungsten can handle re-entry heat just fine, but it will also transfer that heat to whatever it is touching, so you'll still need insulation between the tungsten and everything else.

Link to comment
Share on other sites

54 minutes ago, sevenperforce said:

Tungsten has a cross-sectional ultimate tensile strength that is 90% greater than stainless steel. However, its density is 145% greater than stainless steel. So a tungsten tank with the equivalent strength of a steel tank will be around 30% heavier.

It's also very brittle and becomes more brittle as it gets cold, which makes it VERY poor for holding cryogens.

And before you suppose that a layer of tungsten will work: tungsten can handle re-entry heat just fine, but it will also transfer that heat to whatever it is touching, so you'll still need insulation between the tungsten and everything else.

 

Brittle? As in easy to break?

 

Fine... coat a layer of tungsten over the steel.

As for the heat? Why not have a steel inner wall tank that holds liquid helium (coldest liquid I'm aware of).

 

During reentry the ship opens 'sweating' pore holes that leak evaporating helium.

 

Are you saying the tungsten would break apart from the cold of the helium?

 Because in space there is nothing to disturb the tungsten but ship acceleration, and during reentry the main turbulence is air.

Even if  tungsten may be inclined to break I would think that surely there is a way to stabilze it to prevent that?

Glue?

Edited by Spacescifi
Link to comment
Share on other sites

37 minutes ago, Spacescifi said:

Brittle? As in easy to break?

Brittle, as in breaks instead of flexes. When the Ship flexes, vibrates, or otherwise changes shape ever-so-slightly, the tungsten will chip, shatter, or otherwise flake off.

Early plans for Starship skipped tiles for a “sweating methane” solution, but I guess the math or sims didn’t work out…

More layers of anything adds mass. Mass in spaceflight is bad. 

Link to comment
Share on other sites

10 minutes ago, StrandedonEarth said:

Brittle, as in breaks instead of flexes. When the Ship flexes, vibrates, or otherwise changes shape ever-so-slightly, the tungsten will chip, shatter, or otherwise flake off.

Early plans for Starship skipped tiles for a “sweating methane” solution, but I guess the math or sims didn’t work out…

More layers of anything adds mass. Mass in spaceflight is bad. 

 

Shoot. We need a torchship.

Since the easy solution is.... add mass... but to do that we need more POWAH and we are very limited with that.

 

With enough mass stainless steel and sweating pores would do nicely I think.

 

Just you need torcship level performance if you do not want to waste most of your fuel reaching orbit.

Edited by Spacescifi
Link to comment
Share on other sites

20 minutes ago, Spacescifi said:
1 hour ago, sevenperforce said:

It's also very brittle and becomes more brittle as it gets cold, which makes it VERY poor for holding cryogens.

Brittle? As in easy to break?

A metal can be either brittle or ductile. A more ductile material will be able to handle expansion and contraction without cracking, while a more brittle material will not. Put simply, you can make a very springy spring out of steel; you cannot make a very springy spring out of tungsten. Having a ductile construction material is important for a vehicle like Starship because the tanks will expand and contract as they go through temperature cycles.

Tungsten is also very difficult to work because it is so brittle. It is very hard to bend it at all, but even if you can get it to bend, it will probably crack. Its melting temperature is so high that it is also extraordinarily difficult to weld, and in fact it must be welded in a pure argon atmosphere (or another inert gas) or other stuff will get into the weld and weaken it. Its high melting point means you can't even smelt it; you have to extract it and refine it chemically.

50 minutes ago, Spacescifi said:
1 hour ago, sevenperforce said:

And before you suppose that a layer of tungsten will work. . . .

Fine... coat a layer of tungsten over the steel.

:valawe:

50 minutes ago, Spacescifi said:

As for the heat? Why not have a steel inner wall tank that holds liquid helium (coldest liquid I'm aware of).

If you have a steel inner tank wall with something that will keep the steel cool, then you don't need the tungsten at all. 

To that point, though, there's something fundamental you need to understand about cooling.

Suppose you have a back injury and you want to put an ice pack on your back (which we will assume normally has a surface temperature of 35°C). What will keep your back colder for longer: a pouch of water at 0°C, or a pouch of rubbing alcohol at -10°C? Assume that both pouches contain the same weight of coolant.

You might think the rubbing alcohol would work better, because it's starting at a lower temperature. But you'd be wrong. The heat capacity of water is 74% higher than the heat capacity of rubbing alcohol, so by the time the alcohol temperature goes from -10°C to 35°C, the water will only have gone from 0°C to 25.8°C. That's because water is just better at absorbing heat than rubbing alcohol.

Keeping something from overheating is not a function of how cold your coolant starts out, but rather a function of how fast your coolant can get rid of heat.

If you want to use active cooling with liquid hydrogen or liquid helium or even water, that's perfectly fine. Just know that you'll have to carry that extra liquid hydrogen or liquid helium or liquid water into orbit.

42 minutes ago, Spacescifi said:

We need a torchship.

No, we don't.

42 minutes ago, Spacescifi said:

Since the easy solution is.... add mass... but to do that we need more POWAH and we are very limited with that.

You don't need more power; you need more delta-v.

And simply adding mass is one way to fix it but not the only way.

42 minutes ago, Spacescifi said:

With enough mass stainless steel and sweating pores would do nicely I think.

You don't even need a bunch of mass. The design by Stoke uses an actively-cooled heat shield.

Link to comment
Share on other sites

7 minutes ago, sevenperforce said:

What will keep your back colder for longer: a pouch of water at 0°C, or a pouch of rubbing alcohol at -10°C? Assume that both pouches contain the same weight of coolant.

You might think the rubbing alcohol would work better, because it's starting at a lower temperature. But you'd be wrong. The heat capacity of water is 74% higher than the heat capacity of rubbing alcohol, so by the time the alcohol temperature goes from -10°C to 35°C, the water will only have gone from 0°C to 25.8°C. That's because water is just better at absorbing heat than rubbing alcohol.

Hmmm, but if the rubbing alcohol is not in a pouch, it will evaporate  more easily than the water, and carry away heat via evaporative cooling. So will water, but it evaporates more slowly. I don't know how the calculus works out in terms of heat capacities / heat of vaporization, etc, as to which is actually more effective per unit mass. On a side note, I've noticed spilling heptane on my nitrile gloves at work feels a lot colder than water, even though the water and heptane are at the same temperature, because of the rate of evaporation.

11 minutes ago, sevenperforce said:

You don't need more power; you need more delta-v.

You need the same amount of delta-v. You need more thrust (which likely means heavier engines) to lift it, and more total impulse to impart the same delta-v to a heavier mass, which requires more propellants, and then the "tyranny of the rocket equation" rears its ugly head....

Link to comment
Share on other sites

8 hours ago, Spacescifi said:

1. Tungsten/steel alloy.

2. Tungsten/titanium alloy.

3. Tungsten/alluminum alloy.

I have no idea how well these alloys would perform for starship.

Alloys don't work like that - it's not a dorect merging of pros and cons.

In reality, you have either a majority-tungsten alloy with most of the failings mentioned above, or a tungsten-doped steel with a significant increase in mechanical resilience. There are some tungsten - titanium oxide alloys in the works, apparently, but again, not what you're looking for.

Ultimately, I haven't heard of a good heat shield material capable of also acting as a structural material as well as the material for a cryogenic tank. I don't think they'll get away from either some sort of cooling, or tiles, or scales, or something else that would be a bother. I don't think Shuttle's problematic TPS was a fluke that you can just walk away from.

Link to comment
Share on other sites

13 hours ago, StrandedonEarth said:

if the rubbing alcohol is not in a pouch, it will evaporate  more easily than the water, and carry away heat via evaporative cooling. So will water, but it evaporates more slowly. I don't know how the calculus works out in terms of heat capacities / heat of vaporization, etc, as to which is actually more effective per unit mass. On a side note, I've noticed spilling heptane on my nitrile gloves at work feels a lot colder than water, even though the water and heptane are at the same temperature, because of the rate of evaporation.

Illustrating again why "start with the coldest possible substance" is not a useful exercise in active cooling.

 

13 hours ago, StrandedonEarth said:
13 hours ago, sevenperforce said:

You don't need more power; you need more delta-v.

You need the same amount of delta-v. You need more thrust. . . .

Well, to be pedantic: if you have a vehicle with just enough Δv to make orbit, and then you add mass to that vehicle for heat shielding, then that vehicle no longer has enough Δv to make orbit. So you need more Δv.

And you might not need any more thrust at all; you might have wholly sufficient thrust already. There are any number of ways to get more Δv and "more thrust" or "more power" are not the whole.

Link to comment
Share on other sites

2 hours ago, kerbiloid said:
  Reveal hidden contents

The mods will be in disarray, should they merge it to Orion because it's about torchship (3... 2... 1... Orion), or to SpaceX because Starship!

Combo!

 

 

I like to keep the mods on their toes... subconsciously I guess.

 

But amusing as your prophecy is, this time it won't veer off into cold war relics.

Link to comment
Share on other sites

wonder if anyone has tried regenerative cooling on re-entry surfaces. say with surplus cryofuel. you could use a cermet composite with a corrugated inner layer. this can just be an inner layer of sheet metal with coolant channels pressed into it bonded to another panel with a ceramic outer coating. should be pretty straight forward to manufacture those panels.  the resulting hot fuel can be dumped or used in an air breathing deceleration thruster. 

Edited by Nuke
Link to comment
Share on other sites

@Spacescifi

metallic shields like that have been considered before.  There are two forms that would take. 
 

one would be as a heat sink. It would have to have a lot of mass to be effective (so it has more thermal mass). There are several problems there. First: that extra mass you’ve added. Spacecraft designers try to go the opposite direction: less mass. Another problem is after reentry you now have a lot of thermal energy stored up than if you’d used ablative or shuttle like tiles. All that energy has to go somewhere and the inside of the ship is one of the places it’ll be going. That’s bad. 
 

you CAN design lightweight metallic shields but you’re basically back to tiles again and I’m not sure they’re really any better than silica based tiles. The X-33 would have used metallic tiles as part of its TPS. They were to have been made of titanium and Inconel (a steel nickel chromium alloy). 

Edited by Starwaster
Link to comment
Share on other sites

2 hours ago, Gargamel said:

Stupid stupid air.    Always getting in my way.    Why don't you go somewhere else!?  Nobody likes you, stupid air.

;)

 

Today I learned that Gargamel bicycles a lot...  Or possibly motorcycles.  Or even challenges records at the  Salt Flats.   But I think its bicyclists are most likely to take aeronautic drag personally.

Link to comment
Share on other sites

The common metal heatshield mainstream of 1960s was niobium.

With a niobium front shield, separated from the inner hull with empty space toprevent thermal contact, and tilted relative to it to decrease the heat radiation exchange.

But it's expensive.

***

Between alloys, the titanium alloys were considered to be good as a spaceplane hull material, but again expensive.

Between the titanium alloys, the Ti+W+Mo alloys were beloved by the space romantism of 1950s..1960s, for being stron and heat resistant.

***

Between the heatproof materials, the phenolformaldehyde resins are great and used as heatprotection for reentering things, but the carbon fiber is by order of magnitude better for its extremely low heat conductivity.
It's widely used in the Western reentry vehicles since Minuteman III, but of course not as these silly tiles but winded and filled with glue (the open description of the glue matches the phenolformaldehyde resin).

The nosecones of the Western RV like to be made of silicon carbide and other carbides, and kinda-NASA has tested tantal and hafnium carbides as more heatproof (and published the results), but due to their expensiveness and fragility they are for pointy parts likes the nosecones and ears.

Edited by kerbiloid
Link to comment
Share on other sites

@kerbiloid's list should be expanded. Here are the structural materials proposed for X-15B:

x-15b-airframe-materials.jpg

The thorium would've been mildly radioactive. Skin was, yes, largely niobium. There also was the alternative design from Douglas:

Quote

The Model 684 would have used HK31, an alloy of magnesium, thorium, and zirconium which is no longer in use since the three percent that is thorium makes the alloy radioactive. At the time its relatively low radioactivity was not considered much of a problem, though, and it had the advantage of being much lighter than Inconel X. This meant that the Model 684’s skin could be much thicker, which would reduce costs and would dramatically increase the heat capacity of the plane and keep it from pushing 1000 Celsius on re-entry. The leading wing edges would be made of copper, which would conduct heat away quickly into the rest of the plane.

 

LOL, you couldn't make such a cool name up if you tried: https://en.wikipedia.org/wiki/Mag-Thor

Link to comment
Share on other sites

18 hours ago, wumpus said:

Today I learned that Gargamel bicycles a lot...  Or possibly motorcycles.  Or even challenges records at the  Salt Flats.   But I think its bicyclists are most likely to take aeronautic drag personally.

Nah, just being a jerk in pointing out a typo @Nuke made.   :D

Link to comment
Share on other sites

22 hours ago, Starwaster said:

@Spacescifi

metallic shields like that have been considered before.  There are two forms that would take. 
 

one would be as a heat sink. It would have to have a lot of mass to be effective (so it has more thermal mass). There are several problems there. First: that extra mass you’ve added. Spacecraft designers try to go the opposite direction: less mass. Another problem is after reentry you now have a lot of thermal energy stored up than if you’d used ablative or shuttle like tiles. All that energy has to go somewhere and the inside of the ship is one of the places it’ll be going. That’s bad. 
 

you CAN design lightweight metallic shields but you’re basically back to tiles again and I’m not sure they’re really any better than silica based tiles. The X-33 would have used metallic tiles as part of its TPS. They were to have been made of titanium and Inconel (a steel nickel chromium alloy). 

 

I see... so any ship able to pull off such great mass would likely need super engines to push it too.

 

Assuming the inside of the ship was mostly filled with water, forcing the crew to swim to across to separate air cabins, that could work.

 

With a powerful enough energy input into the propellant, the type of propellant becomes virtually irrelavent.

 

What I am getting at is that the water filled ship could use the water as reaction mass for landing....the ship's body itself would serve as an even bigger fuel tank minus the aired crew cabins... but hallways etc would be underwater.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...