Skylon

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So to recap, it looks like we have just two wings, tucked in a housing that also shields the external propellant flow lines (which is a smart choice, both for servicing and construction reasons and to save as much volume for internal props as possible). 

I'm curious as to the smaller control surfaces we saw before. Are those forward canards? Or are they body flaps mounted underneath the wings, or even articulating on the wings underneath? One of the big unknowns with EDL was the transition from "skydiver" flight to tail-sitting powered descent, with the very serious likelihood of a lawn-dart scenario. Having some control surfaces that act more like elevators would be very useful.

Edited by sevenperforce

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Another thought....

What if they take a page out of the Starhopper playbook and use 3-6 fixed landing legs? Stronger, fewer moving parts, no deployment fairings in the entry airstream, no JASON-3 incomplete deployment risk. The lower risk could permit a slightly smaller footprint.

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10 minutes ago, tater said:

https://www.youtube.com/watch?v=mX2lRNjQyYY

1:22 in there's a skydiver type model.

That's pretty cool. Could watch it for hours tbh.

Do they really need the moving tips if the whole wing can move? Not having them would save a lot of weight.

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I think @sevenperforce is right, and up the thread we have those cruddy renders from that site related document that shows separate legs. I would imagine they end up with "blisters" near the bottom that have legs in them.

 

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Seeing this, I'm thinking there is a fair likelihood that the forward canards are not actually being planned at all, any more. Using only two control surfaces cuts the mechanical failure points in half. Also, note that these are actually substantially higher on the body than the last design, placing their center of pressure much closer to the nose. 

If we assume the "fairing" on the nose is going to be quite draggy (remember, despite cargo, that the tail of this sucker is heavy AF), then it could produce a center of pressure quite high even without forward canards. The center-mounted wings would be able to control pitch and roll quite well, leaving yaw to be handled with thrusters.

Though that does present the question of what those earlier smaller control surfaces are.

With some of the closeups, I think the leading edges are not so sharp as it seems from a distance. So this might be entry-ready as it is.

Finally, keep in mind that we may see these come off and back on a few times if they are doing high-level fitting.

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Hmmmm... I have a feeling it would be quite hard to keep the whole thing balanced during reentry with only two of those "wings". Unless they move up and down on that rail-thing, it seems more reasonable to keep the canards on the ship.

Maybe they will mount the nose first and then cut out holes for the top/front control surfaces.

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Yeah, hard to tell. There has to be a chine  going forward to cover those prop pipes, too.

 

 

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I have another thought: how about legs being the outside part of the wings? In such configuration you would need only one leg near the engines and the other two would use the hinges to spread out after being deployed F9-style at 120° angle from each other.

Such configuration would mess with COM during landing though.

Edited by Wjolcz

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9 minutes ago, Wjolcz said:

Hmmmm... I have a feeling it would be quite hard to keep the whole thing balanced during reentry with only two of those "wings". Unless they move up and down on that rail-thing, it seems more reasonable to keep the canards on the ship.

I am certain they do not move up and down. The "rail-thing" is a propellant line. The wings are fixed-mounted to a rotating element at the base.

If the nose is draggy enough, it ought to balance well enough. One of the things I encountered while testing a Starship mockup shortly after the last version reveal was that it was easier to just keep the forward canards fixed and "fly" on the rear ones as well, since they had so much more authority. You can fold them flush to pitch up, fold them all the way out to pitch down, and fold them differentially to roll. 

9 minutes ago, Wjolcz said:

Maybe they will mount the nose first and then cut out holes for the top/front control surfaces.

I would be very surprised if they didn't take advantage of working closer to the ground on this point. I'll wager that if they don't attach the canards to the fairing on the ground, they won't do forward canards at all.

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As this starts looking like early shuttle concepts, it makes me wonder about contingency operations that could be possible (ie: looks like a lifting body, acts like a lifting body...)

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Anyone else keep thinking of this:

6953507_orig.jpg

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10 minutes ago, tater said:

As this starts looking like early shuttle concepts, it makes me wonder about contingency operations that could be possible (ie: looks like a lifting body, acts like a lifting body...)

If we end up with elevators on the tail, that's possible. But I would be worried about structural integrity in a horizontal landing situation. At most we might see a contingency gliding splashdown in the case of an engine problem.

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Just now, sevenperforce said:

If we end up with elevators on the tail, that's possible. But I would be worried about structural integrity in a horizontal landing situation. At most we might see a contingency gliding splashdown in the case of an engine problem.

That's what I was getting at, exactly.

The guys in the 1960s were pretty sharp, imagine if they had been able to do the computational modeling possible now... All those concept craft leading to Shuttle done the old-fashioned way (though with plenty of testing at smaller scale in an analog way, like plywood and steel lifting body flight tests, etc).

 

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Rear moving fins. That implies that there are forward moving fins.

 

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1 minute ago, Ultimate Steve said:

Rear moving fins. That implies that there are forward moving fins.

 

They'll probably be similar to the forward canards on the previous (triple fixed landing gear) design.

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6 minutes ago, Ultimate Steve said:

Rear moving fins. That implies that there are forward moving fins.

 

Indeed. My speculation has been rapidly invalidated.

Calling them "fins" is really much simpler than "flaperon" or "stallwing" or whatever else we were coming up with. They are without question fins on the way up, after all.

With the legs clearly not going through those fins, I think we have to assume the legs are mounted to the thrust structure. No other way they work.

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Most surprising thing here is the header tanks will be in the upper half, on top of the fuel tanks instead of inside them. Hope that doesn't impact cargo volume that much...

 

Also, how many fins and legs are we getting exactly? Still not clear...

 

Edited by ThatGuyWithALongUsername

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40 minutes ago, sevenperforce said:

I am certain they do not move up and down. The "rail-thing" is a propellant line. The wings are fixed-mounted to a rotating element at the base.

If the nose is draggy enough, it ought to balance well enough. One of the things I encountered while testing a Starship mockup shortly after the last version reveal was that it was easier to just keep the forward canards fixed and "fly" on the rear ones as well, since they had so much more authority. You can fold them flush to pitch up, fold them all the way out to pitch down, and fold them differentially to roll. 

I would be very surprised if they didn't take advantage of working closer to the ground on this point. I'll wager that if they don't attach the canards to the fairing on the ground, they won't do forward canards at all.

Fixed cancards might work, their purpose is to increase nose drag. 

The weird part for me is how they build this. I would expected them to build it more like the hopper. 
The bottom part with the engine mounts and trust structure, bottom bulkhead and the piping with the header tanks above the bulkhead is the most complex part, I would expect them to build this including the skirt as an separate part, then place the rest on top before adding the fins. I assume the fins are have an lever into the engine compartment to control them. 

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12 minutes ago, tater said:
*bunch of tweets*

Gotta love a good Elon tweetstorm...

 

Wonder what the cold gas thrusters are using as fuel? Are they using gaseous CH4 or N2? Apparently, both are available on Mars- the atmosphere is about 2% N2. But is that enough?

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44 minutes ago, ThatGuyWithALongUsername said:

Most surprising thing here is the header tanks will be in the upper half, on top of the fuel tanks instead of inside them. Hope that doesn't impact cargo volume that much...

Yeah, the old plan of using the normal tanks as dewars for the header tanks sounded realy good. Maybe issues with structuraly supporting them under engine power when the main tanks are empty?

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Remember these are flight test prototypes. They only need to be good enough for purpose.

Plumbing the header tanks this way is likely easier.

This version might literally only be for the lower altitude hops, etc.

 

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Won't the cargo bay's volume be huge anyway? They could probably stretch the whole thing a bit, if needed.

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