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6 hours ago, mikegarrison said:

Well, we'll see if it works. But to me the whole thing is starting to sound like they are getting desperate about figuring out their landing gear issues.

Their issues have always been with Starship landing gear. Super Heavy landing gear has always been fairly straightforward, just stick some big fixed ones on there.

This is more about undesigning those legs and moving the shock absorbers out of the booster itself to save mass.

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7 hours ago, mikegarrison said:

Well, we'll see if it works. But to me the whole thing is starting to sound like they are getting desperate about figuring out their landing gear issues.

I suppose another concern is that he wants this to be a land/refuel/refly thing, and moving the booster from a landing spot to a launch pad puts a cramp in that. However, the precision required to come down and land exactly where they took off from is pretty crazy. I mean, even a small wind gust could cause a major disaster.

I imagine the catching mechanism will work on the same principle as Mark Rober's "bullseye every time" dart board.

SimplisticUnderstatedAiredale-size_restr

 

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19 minutes ago, RealKerbal3x said:

Their issues have always been with Starship landing gear. Super Heavy landing gear has always been fairly straightforward, just stick some big fixed ones on there.

This is more about undesigning those legs and moving the shock absorbers out of the booster itself to save mass.

This, saving weight but also reducing reuse time. I think this is a bit over focused as you could just have more superheavy in the pipeline. You would want two as an minimum is case one can not be used but need servicing or worse is lost you are stuck if you only has one but with two your launch rate goes down. 

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15 hours ago, mikegarrison said:

I suppose another concern is that he wants this to be a land/refuel/refly thing, and moving the booster from a landing spot to a launch pad puts a cramp in that. However, the precision required to come down and land exactly where they took off from is pretty crazy. I mean, even a small wind gust could cause a major disaster.

I doubt it. Superheavy is basically a bigger Saturn V. You would need extremely strong winds to have any significant effect. Plus, it will have hot-gas thrusters at both the top and bottom (rather than only the top like the Falcon 9 first stage) for fine translation.

Actually I can calculate that, come to think of it.

Let's say that worse-case scenario you only have two of the ten-tonne RCS thrusters firing continuously, one at the top and one at the bottom. That's 20 tonnes of thrust or 196 kN. What kind of wind can that compensate for? The drag equation says that Fd = Cd*ρ*v2*A/2. So we set Fd = 196 kN and solve for v to find the maximum windspeed that two hot-gas thrusters can compensate for. Solving for v, we get v = sqrt(2*F/(Cd*ρ*A)). The drag coefficient of a cylinder perpendicular to an airflow is approximately 1. Superheavy will have a cross-sectional area of 9 m * 72 m = 648 m2. The density of dry air at sea level is 1.225 kg/m3. Plug and chug and you get v = 22.2 m/s or about 50 mph for us Americans. So unless Superheavy is planning on landing during a severe thunderstorm then it should be just fine.

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17 minutes ago, sevenperforce said:

Plus, it will have hot-gas thrusters at both the top and bottom (rather than only the top like the Falcon 9 first stage) for fine translation.

Do we know that for sure, or are you just speculating?

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If they do actually end up doing this I would expect the "catch" mechanism to also be the stabilizing member during Starship loading, similar to the function of the clasper arms on the F9 transporter-erector:

IMG_3445_1_SpaceXPad39A_KenKremer-1024x6

The arms would hold onto the extended grid fins while the Starship is mated and loaded. At T-1 min, they would fold away and the grid fins would fold down for launch.

At landing, the arms would remain open as Superheavy initially approached, then come together quickly to catch the grid fins. Once caught, they would lower the booster on the launch clamps and remain attached for stability until the next launch.

4 minutes ago, RealKerbal3x said:

Do we know that for sure, or are you just speculating?

I am about 95% confident that Elon specifically said the booster would have aft and forward hot-gas thrusters for fine translation control back when he was talking about landing on the launch clamps.

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14 hours ago, Deddly said:

I imagine the catching mechanism will work on the same principle as Mark Rober's "bullseye every time" dart board.

SimplisticUnderstatedAiredale-size_restr

 

Yes, now scale it up a bit so the dart is 200 ton :) 
Thinking about it using rocket engines to move it around makes sense. 

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2 hours ago, RCgothic said:

 

 

 

tldr:

1)they have some contracts were they can choose between using falcon 9 and starship

2) She is positive about Starship reaching orbit in 2021

3) selling flight proven booster is easier than new ones

4) the sn8 has "de-risked" starship

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2 minutes ago, cubinator said:

Fewer welds means fewer potential points of failure...and fewer parts! :D

The framerate gets pretty bad in LEO, so they're taking steps to reduce the number of objects the universe has to run physics simulations for.

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7 minutes ago, Clamp-o-Tron said:

The framerate gets pretty bad in LEO, so they're taking steps to reduce the number of objects the universe has to run physics simulations for.

It's all the pretty visuals they've got, have you seen those high-res pictures from orbit? If they ditched the fancy clouds and scattering they could launch much more complex ships.

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4 minutes ago, RealKerbal3x said:

SN8's TFR was unlimited altitude as well. It doesn't necessarily mean SN9 is going to go any higher.

Yeah, I got ahead of myself. 

 

 

 

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Just now, cubinator said:

If SN9 is intact after the 12.5 km flight, they should do a 100 km flight with it.

I doubt they'll reuse any Starships until they've stopped rapidly iterating on it. By the time a prototype flies, it's already been made obsolete by the next one.

Seeing SN10 do a 100km flight would be awesome though.

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