SpaceX Updates (Thread 5)


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DocM

Here we go: the SpaceX LC-13 launcher landing complex. Where Falcons will come home to roost.

The contracts between the US Air Force and SpaceX should be signed soon.

Environmental Impact Statement....(PDF)

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PaulRocket

When will they be allowed to land there, assuming that tge barge landing works?

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DocM

Soon as they demonstrate precise control of landings to the USAF 45th Space Wing (which runs the Eastern Range) and the LC-13 mods are finished.

They should be signing the LC-13 contracts within weeks. After that they can start demo and construction.

The demo and construction for the Vandenberg SLC-4W landing pads started 2-3 months ago,

Signage

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SLC-4W launch tower demo

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DocM

Yup. Helodriver ends up in all the cool places at just the right times. The whole thing is moving faster than expected. Can't wait to see the next big story Chris is working on.

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SarK0Y

 They've already done that flight profile without fins, using engine gimbaling and cold gas thrusters. That got them within a few kilometers of the target.

The grid fins are for when it gets to back into the atmosphere, the terminal portion of the return. Grid fins will give them an accuracy of <10 meters without expending more propellants.

Think in terms of the fetching on a modern target arrow. Also very small considering the length of the projectile.

Grid fins have a long history, being used in bombs, missiles, and even the Soyuz launch abort system. They're small for their net effect, light, tough, precise and work in both the subsonic and hypersonic parts of the flight profile.

Yes, it's obvious way for propellant saving's sake. But great accuracy is doubtful because Atmosphere ain't static + bottom of stage is aerodynamic surface too, it can make parasitic drag. Arrow, f.e., has fins & head at the same height + head produces minimal drag. gravity bombs have no so great length & weight as well + needless to mention velocity. Actually, only propulsion can provide most accurate vectoring & minimal lags for manuevers. In short, there gets classical curse -- Accuracy vs. Fuel-gobbling.

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DocM

Yes, it's obvious way for propellant saving's sake. But great accuracy is doubtful because Atmosphere ain't static....

(blather)

>

/sigh

Stop right there. Just stop. Grid fins are used in precision guided munitions. Their whole purpose is to COUNTER atmospheric disturbances that limit accuracy. They're tied into the GPS and other sensors.

I'll end this with the title & reference to an AIAA paper,

Integration of Grid Fins for the Optimal Design of Missile Systems

Timothy W. Ledlow, John E. Burkhalter and Roy J. Hartfield

Auburn University

Auburn University

Auburn University

AIAA Atmospheric Flight Mechanics Conference

DOI: 10.2514/6.2015-1017

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SarK0Y

well, let's Practice will demonstrate who is Right/Wrong :D

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Unobscured Vision

.. and that's why DocM is the OP for most of the Space stuff here on Neowin. Pull up a chair, sit comfortably, and have a Mocha Latte. He knows what he's doing. :yes:

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SarK0Y

 

@elonmusk:

@alankerlin Hydraulics are usually closed, but that adds mass vs short acting open systems. F9 fins only work for 4 mins. We were ~10% off.

DocM, that looks like pure comedy: for each time, launch weight becomes greater -- it's truly dead way. Frankly, i could help to get really cheap LEO, but you know what it takes -- HEIS ;) even if you'll get safe landing, payload weight gets laughable + even one failure kills profit entirely. If you really want cheap LEO, it's based only upon minimal launch weights, as less as possible. In short, think about it. W/o radical turn, Musk is almost done.

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DocM

Thought you said the grid fins wound never get it close to ASDS? So much for your predictions. Now, go troll somewhere else.

------

We have a pic of ASDS. Looks like the loss of the grid fins steering and air-braking authority made it land on one of the extension wings and topple. Some damage to Thrustmaster hardware and the wing, but the former is modular and the wing is just steel. Crane and welder jobs.

Next try looks to be that The DSCOVR launch to L2. Current NET date is Jan. 29, but it may or may not slip a free days.

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IsItPluggedIn

Im a bit confused about this, I thought the grid fins were for higher velocity steering, If it made it all the way to the barge, why does an issue with the grid fins cause issues with landing, or did the grid fins fail so they had to use the engines to steer? 

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malenfant

Edit. [Hypersonic] and subsonic. DocM pointed out they have large effects for their size and probably are effective at very low speeds -relatively.

I'm thinking it came in pitched over, off-axis thrust and possibly obscured landing sensors, hit and snapped off one or more legs...

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SarK0Y

 

Thought you said the grid fins wound never get it close to ASDS? So much for your predictions. Now, go troll somewhere else.

DocM, actually i didn't say that way. the very point was & is: scheme is impracticable -- too inaccurate or too small payload & expensive as well.

 

 

Im a bit confused about this, I thought the grid fins were for higher velocity steering, If it made it all the way to the barge, why does an issue with the grid fins cause issues with landing, or did the grid fins fail so they had to use the engines to steer? 

fins cannot be closed at the end. :)

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DocM

Grid fins have high steering and air braking authority at both hypersonic and subsonic speeds. Where they lose out is in the transonic range, about Mach 0.9 to Mach 1.2. They're key to F9R's terminal approach.

This low speed authority can be seen in a F9R Dev-1 flight where they both steered and rolled the vehicle while it was low & slow..

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SarK0Y

 

@elonmusk

Grid fins worked extremely well from hypersonic velocity to subsonic, but ran out of hydraulic fluid right before landing.

Upcoming flight already has 50% more hydraulic fluid, so should have plenty of margin for landing attempt next month.

Am super proud of my crew for making huge strides towards reusability on this mission. You guys rock!

nice -- a bit windy & you'll run out of hydraulic fluid yet again :rolleyes:  + more fuel needs to slow thing down. :rofl:

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SarK0Y

Grid fins have high steering and air braking authority at both hypersonic and subsonic speeds. Where they lose out is in the transonic range, about Mach 0.9 to Mach 1.2. They're key to F9R's terminal approach.

This low speed authority can be seen in a F9R Dev-1 flight where they both steered and rolled the vehicle while it was low & slow..

so, they're good source of parasitic drag at the final phase of landing. :)

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DocM

Drag and steering. Good enough for Soyuz to use them for crewed launch aborts, and God knows how many precision guided munitions. They're a tool, and a damned effective one.

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SarK0Y

Drag and steering. Good enough for Soyuz to use them for crewed launch aborts, and God knows how many precision guided munitions. They're a tool, and a damned effective one.

launch abort doesn't need extreme accuracy to land. returning stage is entirely different story, guided munitions are damn different story too. you compare orange & apple.

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DocM

Launch abort no, but you're totally ignoring precision munitions. That is 100% applicable.

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SarK0Y

Launch abort no, but you're totally ignoring precision munitions. That is 100% applicable.

those munitions have no that large weight of space launchers. In fact, Musk admitted that there must be extra weight of hydraulic fluid. But why'd it be just 50% more, but not 150% more or so???

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DocM

those munitions have no that large weight of space launchers. In fact, Musk admitted that there must be extra weight of hydraulic fluid. But why'd it be just 50% more, but not 150% more or so???

You fail again. Stop it. Just stop.

The grid fins use an open circuit hydraulic system, meaning the fluids are not recycled. This is common in aerospace to save hardware weight. Musk said their estimate of how much fluid to use was off by 10%, so they're upping it by 50% to have reserves. We're talking about 20-30 liters here.

The US GBU-57A/B Massive Ordnance Penetrator bunker buster bomb uses grid fins and it masses 14,000 kg. A nearly depleted F9 first stage is about 18,000kg.

No practical difference.

massive-ordnance-penetrator-mop-gbu-57ab

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SarK0Y

You fail again. Stop it. Just stop.

The grid fins use an open circuit hydraulic system, meaning the fluids are not recycled. This is common in aerospace to save hardware weight. Musk said their estimate of how much fluid to use was off by 10%, so they're upping it by 50% to have reserves. We're talking about 20-30 liters here.

The US GBU-57A/B Massive Ordnance Penetrator bunker buster bomb uses grid fins and it masses 14,000 kg. A nearly depleted F9 first stage is about 18,000kg.

No practical difference.

massive-ordnance-penetrator-mop-gbu-57ab

Soft landing against bunker penetrator -- nice shot, DocM. Orange vs. Apple. would you like to compare docking w/ anti-aircraft missile??? :D

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