Stoke Space

[tater]

 

[tater]

NSF post today said that in a presentation Stoke said their vehicle is 3t to LEO, full reuse.

[magnemoe]

1 hour ago, tater said:

NSF post today said that in a presentation Stoke said their vehicle is 3t to LEO, full reuse.

I say that is a lot with the to me small upper stage using hydrogen on an two stage rocket even disposable. 

[sevenperforce]

The latest patent from Stoke includes a depiction of a non-axisymmetric heat shield to provide lift during re-entry with 0° AOA:

It's not immediately clear from the patent whether this orientation is imagined as fixed or as moveable.  The patent doesn't discuss it moving, so it's a little tough to figure out exactly how this would interact with the plume coming off the engines themselves, if it's "stuck" like this.

[magnemoe]

2 hours ago, sevenperforce said:

The latest patent from Stoke includes a depiction of a non-axisymmetric heat shield to provide lift during re-entry with 0° AOA:

It's not immediately clear from the patent whether this orientation is imagined as fixed or as moveable.  The patent doesn't discuss it moving, so it's a little tough to figure out exactly how this would interact with the plume coming off the engines themselves, if it's "stuck" like this.

I assume moving it is rotate along the long axis. This let you move left or right and giving you some minor cross range options, you rotate 180 degree to fall faster if overshooting your landing zone. 
Benefit of this upper stage is its small size, you can use an normal truck with an crane to pick it up 

[tater]

 

[sevenperforce]

The small size is just incredible.

[AckSed]

If the SS test was a flying water tower, this is a flying lightbulb.

[tater]

The bottom is 4m in diameter, so larger than F9, less than 1/2 the dia of SS.

[RyanRising]

I wonder how they're handling insulation. It must be inside the outer shell because we can see bare steel there, so something similar to S-IVB maybe?

[darthgently]

2 hours ago, RyanRising said:

I wonder how they're handling insulation. It must be inside the outer shell because we can see bare steel there, so something similar to S-IVB maybe?

It is cooled internally by cryogenic fuel flow much like an engine bell from what I recall.

[sevenperforce]

4 hours ago, darthgently said:

7 hours ago, RyanRising said:

I wonder how they're handling insulation. It must be inside the outer shell because we can see bare steel there, so something similar to S-IVB maybe?

It is cooled internally by cryogenic fuel flow much like an engine bell from what I recall.

That's how they are cooling the heat shield, but insulation is a different issue entirely -- keeping the propellant from boiling off due to ambient heat transferred through the skin.

To @RyanRising's question -- my guess is that these early hopper prototypes have simply dispensed with insulation altogether. The low fineness of the stage minimizes surface area, anyway. For short hops and even suborbital hops, the amount of propellant lost to boiloff is going to be relatively negligible.

Once they have an actual orbital vehicle under construction, we'll see whether they do some sort of insulation. It may be that the additional weight of insulation would be greater than the weight of propellant lost to boiloff anyway, and so eschewing insulation entirely is the best approach.

[magnemoe]

17 minutes ago, sevenperforce said:

That's how they are cooling the heat shield, but insulation is a different issue entirely -- keeping the propellant from boiling off due to ambient heat transferred through the skin.

To @RyanRising's question -- my guess is that these early hopper prototypes have simply dispensed with insulation altogether. The low fineness of the stage minimizes surface area, anyway. For short hops and even suborbital hops, the amount of propellant lost to boiloff is going to be relatively negligible.

Once they have an actual orbital vehicle under construction, we'll see whether they do some sort of insulation. It may be that the additional weight of insulation would be greater than the weight of propellant lost to boiloff anyway, and so eschewing insulation entirely is the best approach.

I see it likely they use some insulation between the bottom heat shield and the equipment there as the steel shield can manage much higher temperature than the equipment. For the sides this might be an issue, the cone reduce the  heating but you still get some radiation heating. 

[sevenperforce]

33 minutes ago, magnemoe said:

I see it likely they use some insulation between the bottom heat shield and the equipment there as the steel shield can manage much higher temperature than the equipment. For the sides this might be an issue, the cone reduce the  heating but you still get some radiation heating. 

By the time they are doing re-entry, the tanks are over 90% empty. Autogenous-press gas is a relatively good insulator. At the most they might need a little something around the base to deal with radiation heating, but even there the emissivity of stainless steel is probably working in their favor.

Have we ever seen a cutaway of their tank layout? If insulation does become an issue, I could see them doing concentric tanks or some kind of conical arrangement. Perhaps this:

Grey is the engine/heat shield section, while blue is a toroidal LOX tank and yellow is the LH₂ tank. This way, the LOX tank does double-duty as double-wall insulation for the hydrogen tank during re-entry, because the remaining liquid hydrogen will be well below the single-walled region. Of course then you have to deal with insulation on the inner common bulkhead between the LOX and the hydrogen.

[magnemoe]

1 hour ago, sevenperforce said:

By the time they are doing re-entry, the tanks are over 90% empty. Autogenous-press gas is a relatively good insulator. At the most they might need a little something around the base to deal with radiation heating, but even there the emissivity of stainless steel is probably working in their favor.

Have we ever seen a cutaway of their tank layout? If insulation does become an issue, I could see them doing concentric tanks or some kind of conical arrangement. Perhaps this:

Grey is the engine/heat shield section, while blue is a toroidal LOX tank and yellow is the LH₂ tank. This way, the LOX tank does double-duty as double-wall insulation for the hydrogen tank during re-entry, because the remaining liquid hydrogen will be well below the single-walled region. Of course then you have to deal with insulation on the inner common bulkhead between the LOX and the hydrogen.

Good points but I don't think you need the toroidal tank, as the tank is rounded at the rear the rest hydrogen will gather in the center, if needed make an thin wall say 30 cm from the outer hull and pump hydrogen stuck here into the center part then you start to feel drag so  so its only pressurized gas near the hull. 

[sevenperforce]

44 minutes ago, magnemoe said:

Good points but I don't think you need the toroidal tank, as the tank is rounded at the rear the rest hydrogen will gather in the center, if needed make an thin wall say 30 cm from the outer hull and pump hydrogen stuck here into the center part then you start to feel drag so  so its only pressurized gas near the hull. 

If the design is typical then you would most likely have the LOX tank at the bottom to begin with; this also provides for better stability on re-entry. So there's some concern that LH₂ would be forced to the outer perimeter.

In the various published images I haven't seen any downcomer on the outside of the stage. Of course they could have the LOX tank at the top and a central downcomer.

[RyanRising]

On 9/7/2023 at 6:09 AM, sevenperforce said:

That's how they are cooling the heat shield, but insulation is a different issue entirely -- keeping the propellant from boiling off due to ambient heat transferred through the skin.

To @RyanRising's question -- my guess is that these early hopper prototypes have simply dispensed with insulation altogether. The low fineness of the stage minimizes surface area, anyway. For short hops and even suborbital hops, the amount of propellant lost to boiloff is going to be relatively negligible.

Once they have an actual orbital vehicle under construction, we'll see whether they do some sort of insulation. It may be that the additional weight of insulation would be greater than the weight of propellant lost to boiloff anyway, and so eschewing insulation entirely is the best approach.

I'm not sure that's plausible. For one, we can see that in the pic they showed of a WDR that there isn't ice on the tank when that happens with things much less cold than liquid hydrogen on uninsulated tanks. Secondly, because of its unique properties - not just freezing water but often liquefying air through a tank wall if not insulated - I don't believe even for short hops or static fires that the boiloff losses would be negligible. Even with insulated tanks, remember that some hydrogen rockets have pour twice their fuel capacity into a tank before it fills.

Edited September 9, 2023 by RyanRising

[darthgently]

11 hours ago, RyanRising said:

Even with insulated tanks, remember that some hydrogen rockets have pour twice their fuel capacity into a tank before it fills.

Well, there is the initial cooling of the tank itself to take into account

[magnemoe]

12 hours ago, RyanRising said:

I'm not sure that's plausible. For one, we can see that in the pic they showed of a WDR that there isn't ice on the tank when that happens with things much less cold than liquid hydrogen on uninsulated tanks. Secondly, because of its unique properties - not just freezing water but often liquefying air through a tank wall if not insulated - I don't believe even for short hops or static fires that the boiloff losses would be negligible. Even with insulated tanks, remember that some hydrogen rockets have pour twice their fuel capacity into a tank before it fills.

Shuttle and SLS is insulated on the outside, could you insulate the inside instead? Benefit is that you have no risk of damaging the fragile insulation while handling. But then you needed to make it pretty hydrogen tight. should be doable I think. It will be a bit heavier than on outside like on the shuttle tank but if would be reusable. 

[tater]

 

[tater]

Picture needed embiggening

[Kartoffelkuchen]

Can the engines gimbal? From the way they are integrated into the heatshield I'd assume they can't. So they'd have to resolve to shutting of the engine on the other side in case of a failure to balance the thrust. 
Let's hope they have their engine reliability in check then! I'm >stoked to see this fly

Edited September 12, 2023 by Kartoffelkuchen

[darthgently]

9 minutes ago, Kartoffelkuchen said:

Can the engines gimbal? From the way they are integrated into the heatshield I'd assume they can't. So they'd have to resolve to shutting of the engine on the other side in case of a failure to balance the thrust. 
Let's hope they have their engine reliability in check then! I'm >stoked to see this fly

As I recall, differential thrust is the plan for overall vectoring, no individual gimbaling.  So yeah, failure of one means losing two!  I may be mis-recalling

[tater]

16 minutes ago, Kartoffelkuchen said:

Can the engines gimbal? From the way they are integrated into the heatshield I'd assume they can't. So they'd have to resolve to shutting of the engine on the other side in case of a failure to balance the thrust. 
Let's hope they have their engine reliability in check then! I'm >stoked to see this fly

Think it's 1 engine, multiple combustion chambers (with throttles).

[Royalswissarmyknife]

I wont be surprised if Stoke does 3 hop's before New Glenn ever fly's.