Skylon

SpaceX Discussion Thread

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18 hours ago, Bill Phil said:

DC-X was a test article. A fairly successful one at that. “Not invented here” killed DC-X once NASA gained control of the program. Instead NASA began development of X-33 and Venturestar... which couldn’t even have a successful demonstration.

"Not invented here" couldn't possibly be as bad for the program as being sold as SSTO.  That makes it far to easy for anyone wanting to help themselves to DC-X's budget.

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Thoughts on one of the older ways of rocketry: composite tanks inside a metal hull?

How about a definitely counter-intuitive variant: metal hull-tank walls with composite bulkheads?

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I remember watching as a fiberglass part was changed to extruded plastic to save costs. Within a year the extruded plastic was changed to fiberglass to save costs. No kidding. (I think the real cost savings had to do with vendor contracts.)

Material changes are pretty common because every material has advantages and disadvantages. It is certainly not the case that composite is always better than metal (or even always lighter).

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Does anyone have accurate numbers for B5 stage 1 dry and wet masses (without legs and fins)? I tried to google it, and numbers are all over the place, from 16t to 25t dry mass, for example.

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16 hours ago, mikegarrison said:

I remember watching as a fiberglass part was changed to extruded plastic to save costs. Within a year the extruded plastic was changed to fiberglass to save costs. No kidding. (I think the real cost savings had to do with vendor contracts.)

Material changes are pretty common because every material has advantages and disadvantages. It is certainly not the case that composite is always better than metal (or even always lighter).

I see this frequently as well. It will be fiberglass -> plastic (piece part cost save, yay!) then plastic -> fiberglass (warranty cost save, yay!). Sometimes cost save ideas are really good and/or confusing and sometimes they're not well thought out and end up costing more in the long run. And you're right, sometimes vendor contracts dictate why designs end up being a certain way. I can think of several parts off the top of my head that haven't changed in many years because they're locked in at a contract price that's favorable. 

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No net? Is that really going to be safe for reuse? On a somewhat related note , how does the force on the faring at max q compare to the force from crashing into the ocean? ( I suppose that they don’t even compare, thus why fairings have never been reused )

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It seems reasonable that if they took steps to protect the inside from casual seawater splash and spray, and that it lands softly enough to not do structural damage, then reuse should be fairly straightforward. After all, a fairing half would make a decent boat hull and has to protect the payload from rain and thunderstorms. 

I start to think they could add a small electric outboard motor (and a sail if the winds are favourable), some solar panels, maybe some keel ridges, and it could sail itself home. Maybe they should buy a boatmaker to make self-returning fairings lol

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I'd be inclined to place an inflatable wall along the bottom semicircle of each half, then it's really protected from surf.

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1 hour ago, tater said:

I'd be inclined to place an inflatable wall along the bottom semicircle of each half, then it's really protected from surf.

Rater make the inside parts water resident, fiber glass don't take damage from seawater, you will has to do an full service on all mechanical parts. Protect electronic.  
I assume is acoustic panels on the inside This might easy be the main issue as they are likely to absorb water and might be glued to fairing. 

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5 hours ago, tater said:

I'd be inclined to place an inflatable wall along the bottom semicircle of each half, then it's really protected from surf.

So basically they need to be giant stand-up paddle boards. 

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If it can just splash and repair this eliminates sense of the landing legs, landing accuracy, and other things they are famous for.
Upd.: the drone barges, the net.

P.S.
They could just land splash it into a pool of drink water.

P.P.S.
Or in Louisiana.

Edited by kerbiloid

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13 minutes ago, kerbiloid said:

other things they are famous for.

yAokXBF.jpg

 

13 minutes ago, kerbiloid said:

... splash it into a pool of drink water [...] Or in Louisiana.

Falcon vs. Gators.

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1 hour ago, kerbiloid said:

If it can just splash and repair this eliminates sense of the landing legs, landing accuracy, and other things they are famous for.

The first stage is a little bit more sensetive to water.

36 minutes ago, Xd the great said:

Roasting gators. Mmmm

Or not. Consider the Worst Case Scenario.

worst_case_scenario.png

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14 minutes ago, DDE said:

The first stage is a little bit more sensetive to water.

I just followed the words:

Quote

Seems likely that we’ll be able to reuse fairings that soft-landed in the ocean. May not need net at all.

They should protect the nozzles with water-proof caps instead of the legs.

Also, drink water is less agressive than sea water.

Edited by kerbiloid

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2 hours ago, kerbiloid said:

 

They should protect the nozzles with water-proof caps instead of the legs.

Also, drink water is less agressive than sea water.

The biggest problem is the corrosion. Metals built for high temperatures may not be corrosion resistant and vice versa.

Also, they need to practice pinpoint landings on the Starship anyway.

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16 hours ago, StrandedonEarth said:

It seems reasonable that if they took steps to protect the inside from casual seawater splash and spray, and that it lands softly enough to not do structural damage, then reuse should be fairly straightforward. After all, a fairing half would make a decent boat hull and has to protect the payload from rain and thunderstorms. 

I start to think they could add a small electric outboard motor (and a sail if the winds are favourable), some solar panels, maybe some keel ridges, and it could sail itself home. Maybe they should buy a boatmaker to make self-returning fairings lol

I don’t know about reasonable but that would be so cool!

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35 minutes ago, KSK said:

I don’t know about reasonable but that would be so cool!

Sounds suspiciously like the detachable engines on a new rocket.

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11 hours ago, kerbiloid said:

I just followed the words:

Quote

Seems likely that we’ll be able to reuse fairings that soft-landed in the ocean. May not need net at all.

They should protect the nozzles with water-proof caps instead of the legs.

Also, drink water is less agressive than sea water.

You quoted a statement about reusing fairings that went for a swim. The first stage's reusability is in no way dictated by the landing conditions after which a fairing may be reused.

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On 12/12/2018 at 9:14 AM, kerbiloid said:

They should protect the nozzles with water-proof caps instead of the legs.

Right after the retroburn? Fastest cap in the West.

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I think they should use water deluge systems on the landing pad. you know, for cooling down the booster after landing. if they ever do it it would be a good water show.

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24 minutes ago, nasa legolas said:

I think they should use water deluge systems on the landing pad. you know, for cooling down the booster after landing. if they ever do it it would be a good water show.

Does the booster really need cooling after landing? Sure, the engine bells are hot and the rocket just spent some time in supersonic wind, but right after that it spends a bunch of time in regular wind which tends to be cooling.

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