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Starship Prototype Unveiled

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Re: Starship Prototype Unveiled

#221

Post by nitrogen »

MR4D wrote: post #193
balfirevic wrote: post #141

Earlier quoted context omitted.

> I think the military was looking at a similar material to replace depleted uranium with something non-radioactive I thought the point of depleted uranium projectiles was simply the density of uranium, giving them large impact energy for a given volume. If that's the case, titanium (4.5 g/cm^3) will not even be as good as steel (8 g/cm^3), let alone uranium (19 g/cm^3).

Tungsten. https://www.military.com/dodbuzz/2018/05/14/air-force-debate...

I hope I am never in a position to hear that sound in person.

Re: Starship Prototype Unveiled

#222

Post by hadlock »

cryptoz wrote: post #44
DanCarvajal wrote: post #33

Earlier quoted context omitted.

Starship could have Falcon Heavy level of delays (which I think it will) and still beat SLS.

FH was 5 years+ behind schedule before it was built and launched. Starship already has multiple constructions going on, with multiple prototypes to test and multiple full-size vehicles planned quickly. In 2011, FH was supposed to have "arrival at launch site" by 2H 2012. It first launched in 2018 (after arriving at launch site in 2018 not 2012). The same level of delay would mean the first Starship does not reach orb…

The center core of the Falcon Heavy has been described by Musk as effectively an entirely new rocket, due to the million pound lateral forces holding the three rockets together. It's not just three Falcon 9 strapped together.

Re: Starship Prototype Unveiled

#223

Post by adrianN »

rjf72 wrote: post #219
hoorayimhelping wrote: post #20

380s for ISP for the Raptor vacuum engine seems durn good, considering the tradeoffs between hydrogen and methane. The most efficient engines we've flown, the RL-10 [0] (used on the Delta IV and Atlas rockets as part of the Centaur Upper Stage) and the RS-25 [1], (the Space Shuttle Main Engine) get around 450-460s for their specific impulse. These engines use liquid hydrogen and liquid oxygen. The issue with liquid h…

You missed one of the most important parts about methane as well: The Sabatier Reaction [1] Hydrogen + CO2 => Methane + Water This is an extremely important reaction. Mars, for instance, has effectively unlimited Hydrogen and CO2 which also means effectively unlimited Methane and Water. How just absurdly convenient is that? But it also plays a major role in things like life support. We breathe out CO2. On Earth where…

If you invest more energy you can also turn Methane into longer chain hydrocarbons and produce things like plastics or lubricants.

Re: Starship Prototype Unveiled

#224

Post by rjf72 »

doomlaser wrote: post #186
hoorayimhelping wrote: post #20

380s for ISP for the Raptor vacuum engine seems durn good, considering the tradeoffs between hydrogen and methane. The most efficient engines we've flown, the RL-10 [0] (used on the Delta IV and Atlas rockets as part of the Centaur Upper Stage) and the RS-25 [1], (the Space Shuttle Main Engine) get around 450-460s for their specific impulse. These engines use liquid hydrogen and liquid oxygen. The issue with liquid h…

I'm no rocket scientist, so bear that in mind, but something has been bugging me about the flight paths for this vehicle [0]. It has to make some very large, specific orientation changes several times during descent, using the heat shield on one side of the vehicle, and then only rotating to upright orientation in the lower atmosphere, after quite a lot of falling sideways. The orientation maneuvers seem much more co…

A lot of the complexity is hidden in the second video. It's the exact same deal, it just doesn't look like it. In particular those innocuous 'waffle irons' on the side play an incredibly important role. You miss the scale in the video thanks to how big everything is. Those fins are each 4' x 5' large. And each of them can independently yaw/pitch/roll. And of course the exact angle that the rocket is at when it fires its boostback (as well as when it's coming down), exactly how long the boostback is fired, and a large number of other variables all need to be lined up exactly perfectly. Otherwise you end up literally thousands of miles from your destination, run out of fuel, or otherwise condemn your mission in a surprisingly large number of innovative ways.

The big difference you're seeing compensated for is that Mars atmosphere is less than 1% dense as Earth. So to slow yourself down you need a much larger exposed surface area. Do that exact maneuver on Earth and you'd get an 'unplanned rapid disassembly' during reentry thanks to the thicker atmosphere. That danger and complexity is also something that's hidden.

I cannot recommend Kerbal enough for anybody even vaguely interested in space. Just absurdly fun and does really help you get a feel for all of these issues.

Re: Starship Prototype Unveiled

#225

Post by hadlock »

ryanmarsh wrote: post #166

How do they plan to get 100 tons of cargo from atop the starship down to the surface of Mars? Do you use a crane? I mean, cranes are heavy, right?

Cranes aren't especially heavy. You would need a boom to extend 2x the maximum dimension of the cargo hatch, so probably 8 feet, out past the exterior skin, plus some dyneema or steel cable, plus a winch motor of some sort. Not 100 lbs but probably less than 1000.

Re: Starship Prototype Unveiled

#226

Post by iamgopal »

codeulike wrote: post #8

I totally understand why they've gone for that design but the welded together steel plates really make me think of the sort of thing Wallace and Gromit would build.

We work with multiple tens of ton of SS steel per month, and I would have never thought this heavy thing could fly with all the stress of the sky. I hope it fly good.

Re: Starship Prototype Unveiled

#227

Post by fastball »

woodandsteel wrote: post #176
AimForTheBushes wrote: post #122

Earlier quoted context omitted.

I doubt SpaceX would be a thing if Elon didn't have engineering capabilities.

I have read that when he gets interested in a technical area, he reads a ton of books at a remarkably fast pace, remembers everything he reads, next analyses everything at a fundamental level, and finally comes up with a radically better plan than anyone else has before. I guess you could call that engineering capabilities.

If that's not engineering I don't know what is.

Re: Starship Prototype Unveiled

#228

Post by nerdponx »

NASA is still waiting for SpaceX to complete the Crew Dragon spacecraft that will fly astronauts to and from the International Space Station. The space agency has picked SpaceX (and another company, Boeing) to provide commercial crew flights to the station.

While SpaceX did launch an unpiloted Crew Dragon test flight to the space station this year, a subsequent abort system test failed, leading to the destruction of the vehicle. SpaceX aims to resume abort system tests later this year ahead of the first crewed test flight.

NASA Administrator Jim Bridenstine, it seems, is not happy with the years-long delays of Crew Dragon, as well as Boeing's Starliner spacecraft, especially after seeing SpaceX build Starship Mk1 this year ahead of its own test flight.

"I am looking forward to the SpaceX announcement tomorrow," Bridenstine wrote on Twitter Friday. "In the meantime, Commercial Crew is years behind schedule. NASA expects to see the same level of enthusiasm focused on the investments of the taxpayer. It's time to deliver."

Interesting.

Re: Starship Prototype Unveiled

#229

Post by XorNot »

elif wrote: post #165
XorNot wrote: post #163

Earlier quoted context omitted.

Uh what? This is exactly the inverse of what happens. Quenching leads to stronger, more flexible steel. Slow cooling leads to harder, but more brittle steel. The reason is grain structure - slow cooling allows larger grains, which don't allow the movement of dislocations as freely, but the loss of flexibility costs in ultimate tensile strength.

Please cite your correction or delete it if you find you are in error. I have provided my 2 sources which are in addition to my peer and personal experience in blacksmithing.

What I get for combining some rusty mat-sci with layman's understanding of terms. You're right regarding the specific processes

Re: Starship Prototype Unveiled

#230

Post by kwk1 »

CriticalCathed wrote: post #215
elif wrote: post #165

Earlier quoted context omitted.

Please cite your correction or delete it if you find you are in error. I have provided my 2 sources which are in addition to my peer and personal experience in blacksmithing.

I don't know about his general claim, but a detail within his comment is right. Smaller grain size leading to stronger material -- this is a result of more grain boundaries as the scale of the grain goes down. Hall-Petch strengthening.[0] A secondary effect is that with smaller grains oriented in random directions the metal is more resistant in general from stresses in all directions; whereas with larger grains you t…

The GP comment is claiming the opposite--that larger grain size results in a stronger material.
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