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SpaceX Discussion Thread

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Yeah, the trouble is likely the electronics, rcs stuff, chute related things, etc.

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32 minutes ago, Green Baron said:

It astonishes me that the thing has no visible traces of reentry, like a burnt surface.

It's not going appreciably faster than a first stage on re-entry. Most or all of the soot on a Falcon 9 first stage is the result of the retropropulsive burns; you can see this in some of the really clear RTLS videos. Plus, it's much much fluffier than a first stage so it starts decelerating much higher.

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3 hours ago, tater said:

A reality check. Much has said that the fairings cost 6M. Call it 5M. If every launch this year reused fairings, they'd pocket almost 150 Million dollars. Their launch prices are about the same, reused or not. Every reused booster is 10s of millions they pocket. The whole point of this revenue is to develop the next gen vehicle. Fairing reuse is free money (minus dev costs, which seem to be fairly minimal), and once accomplished, moves BFR forward (since the composite people then partially move to making the grasshopper).

A lot of this depends on Space-x's extreme manifest: presumably things like Proton and Soyez launch as often, but little else does.  I'd expect that you would at least consider using aluminum  or steel fairings for lightweight missions, but I doubt many rockets have enough "launched at the low end of the range" missions to justify the design.  It takes a lot of faith in your manifest to go out and keep spending money on your design, even if you expect to start 'picking up $5M every launch'.

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 Guys, can we please avoid ad-hominem attacks on this forum? If somebody wants to rain on our parade, it's better to just ignore them rather than arguing with them.

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24 minutes ago, softweir said:

 Guys, can we please avoid ad-hominem attacks on this forum? If somebody wants to rain on our parade, it's better to just ignore them rather than arguing with them.

Agreed. We are all space geeks here and we should celebrate that. We won't always agree, but we shouldn't go making the disagreements personal.

Best,
-Slashy

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3 hours ago, tater said:

Yeah, the trouble is likely the electronics, rcs stuff, chute related things, etc.

There is a trick to helping many metals (aluminum, copper, stainless steel, even galvanized). Take the metal when new, hit it very quickly with acid, say 0.01 M phosphoric with a trace of hydrocloric (10 ppm) (Iron and Aluminum will generate hydrogen gas in the presense of HCl and will pit so HCl is only trace, just enough to form monovalent anions to remove superficial metal salts). In the presence of nitrogen gas, helium or carbon dioxide rinse the metal free of the acid (or a solution sodium trace reducing agent and purged of all O2) and the briefly hit it with sodium bicarbonate to neutralize the acid (in this state the metal is extremely prone to corrosion so the next step must be performed rapidly. Rinse the bicarbonate off,  get absolutely distilled water (No CO2) add denatured limestone (lime Cal, calcium oxide)...about a quarter teaspoon per gallon and allow the metal to soak in this solution while the metal is very fresh. Under basic conditions (like sea water) this will for short periods resist the corrosion. The calcium sticks like glue to the metal in a single layer, when it is exposed to the atmosphere CO2 binds the calcium forming a very thin layer of calcium carbonate that can only be removed with acid.

 

 

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18 hours ago, Green Baron said:

Salt water is more a problem for metals, corroding them chemically and through electrolysis if a current is present.

It astonishes me that the thing has no visible traces of reentry, like a burnt surface.

 

17 hours ago, sevenperforce said:

It's not going appreciably faster than a first stage on re-entry. Most or all of the soot on a Falcon 9 first stage is the result of the retropropulsive burns; you can see this in some of the really clear RTLS videos. Plus, it's much much fluffier than a first stage so it starts decelerating much higher.

Yeah, this. I was going to say high drag to mass ratio :P

14 hours ago, PB666 said:

There is a trick to helping many metals (aluminum, copper, stainless steel, even galvanized). Take the metal when new, hit it very quickly with acid, say 0.01 M phosphoric with a trace of hydrocloric (10 ppm) (Iron and Aluminum will generate hydrogen gas in the presense of HCl and will pit so HCl is only trace, just enough to form monovalent anions to remove superficial metal salts). In the presence of nitrogen gas, helium or carbon dioxide rinse the metal free of the acid (or a solution sodium trace reducing agent and purged of all O2) and the briefly hit it with sodium bicarbonate to neutralize the acid (in this state the metal is extremely prone to corrosion so the next step must be performed rapidly. Rinse the bicarbonate off,  get absolutely distilled water (No CO2) add denatured limestone (lime Cal, calcium oxide)...about a quarter teaspoon per gallon and allow the metal to soak in this solution while the metal is very fresh. Under basic conditions (like sea water) this will for short periods resist the corrosion. The calcium sticks like glue to the metal in a single layer, when it is exposed to the atmosphere CO2 binds the calcium forming a very thin layer of calcium carbonate that can only be removed with acid.

 

 

Different metals can be passivated differently. Another nice thing that works on multiple metals (with not nice reagents) is to give it a quick dip in >10% hydrofluoric acid. The metal is oxidised to fluoride on the surface layer only and if you can get a coherent coating it is usually even better than the above method. Well, except for HF being well toxic and corrosive to almost everything :P

 

EDIT - or you can just paint it, which it probably the most common solution?

Edited by Antstar

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30 minutes ago, Antstar said:

Different metals can be passivated differently. Another nice thing that works on multiple metals (with not nice reagents) is to give it a quick dip in >10% hydrofluoric acid. The metal is oxidised to fluoride on the surface layer only and if you can get a coherent coating it is usually even better than the above method. Well, except for HF being well toxic and corrosive to almost everything :P

 

EDIT - or you can just paint it, which it probably the most common solution?

For chemical corrosion yes. For galvanical not. Aluminiumboats need a very thorough electric system. Since not everybody in a marina takes equal care, sacrificial anodes must be placed that are higher in the galvanical order (Zinc). Parts like the propeller or in- and outlets, usually of bronze, must be protected likely.

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Just now, sevenperforce said:

BOTH!!?? BOTH! WHAT IS THIS SORCERY!?!?

They just know how to quickload.

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7 minutes ago, Green Baron said:

For chemical corrosion yes. For galvanical not. Aluminiumboats need a very thorough electric system. Since not everybody in a marina takes equal care, sacrificial anodes must be placed that are higher in the galvanical order (Zinc). Parts like the propeller or in- and outlets, usually of bronze, must be protected likely.

Yes and no. This applies most for things that will spend a lot of time in the water. Galvanic corrosion almost always starts with pitting, which changes the composition of the alloy slightly and accelerates the corrosion. It also applies to things that were cheaply (badly) painted and then possibly scraped due to collisions with anything, including while docking or from tug-boats. Growing barnacles on the bottom and their excretions also plays a factor below the waterline

EDIT- agreed about props. but i think this would not be a problem for rocket parts. However, getting the water out of all the mechanical bits and pieces would be a pain

Edited by Antstar

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4 minutes ago, sevenperforce said:

BOTH!!?? BOTH! WHAT IS THIS SORCERY!?!?

They swam and they picked them out of the water ? Somehow i feel like i am missing something ... :-)

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5 minutes ago, sevenperforce said:

BOTH!!?? BOTH! WHAT IS THIS SORCERY!?!?

They probably just used a crane to put them onboard. Those fairings are probably quite buoyant in calm seas.

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I'd imagine that it would be easier if both fairings had chutes, etc for balance, or just ease of construction (that they would be identical). They were only trying to catch one, because if the net doesn't work, they'd not want to waste money on 2 ships fitted out.

So both slashed down.

splashed, lol

Edited by tater

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7 minutes ago, Green Baron said:

They swam and they picked them out of the water ? Somehow i feel like i am missing something ... :-)

Oh, I was just being overly enthusiastic, since to date we only heard of one entering successfully on each mission.

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3 minutes ago, tater said:

So both slashed down.

No wonder Mr. Steven missed the fairing. It was terrified of these violent slasher fairings.

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If the fairings had deployable outboards, they could come home themselves.

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46 minutes ago, Rakaydos said:

One and a half.

1479397.jpg

Aww...

 

Still, good effort. Learn it up then make a better one...

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A thought...

I'm sure most of us are not so blinded by the His Muskiness to think that BFS will be allowed to fly crew without a launch escape system capable of zero-zero launch/landing abort. Certainly not for NASA.

What's the most mass-efficient, fool-proof method to give a crew of 7 a failsafe abort mode that ensures LOV cannot become LOC?

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9 minutes ago, sevenperforce said:

A thought...

I'm sure most of us are not so blinded by the His Muskiness to think that BFS will be allowed to fly crew without a launch escape system capable of zero-zero launch/landing abort. Certainly not for NASA.

It had a launch escape system in the front section right? Or was that just the ITS?

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7 minutes ago, sevenperforce said:

A thought...

I'm sure most of us are not so blinded by the His Muskiness to think that BFS will be allowed to fly crew without a launch escape system capable of zero-zero launch/landing abort. Certainly not for NASA.

What's the most mass-efficient, fool-proof method to give a crew of 7 a failsafe abort mode that ensures LOV cannot become LOC?

Having enough saftey rating on the Raptor to run the VacRaptor at sea level in an emergency, with minimal flow separation inside the mars-rated nozzles.

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4 minutes ago, NSEP said:

It had a launch escape system in the front section right? Or was that just the ITS?

Both the ITS and the BFR expected to use the upper stage as a launch escape system, in the IAC presentations. That's not a great idea; you're depending on turbopumps to spin up instantly and all the engines to come to full throttle fast enough to escape an exploding booster with a TWR barely over 1. More importantly, there's no LES for an upper-stage problem, like CRS-7/AMOS-6, and there's no abort mode on landing. 

10 minutes ago, Rakaydos said:

Having enough saftey rating on the Raptor to run the VacRaptor at sea level in an emergency, with minimal flow separation inside the mars-rated nozzles.

Still has a low abort TWR and no contingency for a lot of other possible failures. What happens if you have a leak in your LOX header tank? What if there's MMOD damage to one of the winglets? What if a landing leg fails?

Obviously, no launch abort system is going to help you on Mars or on the Moon...but for LEO operations, you want the ability to abort safely at any point from takeoff to touchdown.

You don't want another Challenger (some part of the booster coming loose and hitting the orbiter and causing it to break up) and you don't want another Columbia (some sort of heat shield damage causing vehicle breakup during entry). Without a lifeboat escape, both remain issues for BFS.

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