Lukaszenko
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Posts posted by Lukaszenko
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2 hours ago, NSEP said:
An elegant idea. Unfortunately, a big drawback with it, or pretty much any artificial gravity idea, it that it would drastically reduce the amount of usable space you have.
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3 hours ago, insert_name said:
Iridium next/grace FO scheduled for the 21st
http://spacenews.com/iridium-to-complete-next-generation-satellite-deployment-by-this-fall/
Same article states that they've already deorbited a large number of the old-school versions of the satellites.
RIP Iridium flares
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2 hours ago, cubinator said:
I think the general idea was that once they get good at landing the first fairing, they'll buy more boats.
I'm guessing that the boat is cheaper than the fairing (half).
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9 hours ago, StrandedonEarth said:
Into nearly identical orbits, with the mother of all cubesat dispensers...
If the cost-to-orbit is so cheap, maybe it's no big deal to simply add a super-cheap propulsion, like a compressed air tank with a de Laval nozzle, for example. I wonder how much delta v you could get out of something like that.
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Yeah, it looks like they got confirmation of booster destruction, but immediately after a "but don't say anything!!"...and then you can kind of see them backpedal and try to hide their emotions.
As for the free ride on the Falcon, would have been a perfect opportunity to test that Cannae drive and put the whole thing to bed. Most of the arguments against doing just that seemed to be of the "putting it in space is too expensive" variety.
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Apparently there's also unknown and large risks when lighting up and firing 27 engines simultaneously as opposed to one, or only 9. Resonances, vibrations, whotf knows what else.
If you ask me, if one works then you just add 26 more exactly the same. Should be mundane.
Good thing they're not asking me
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12 minutes ago, Jaff said:
No doubt but they’ve learnt from that and have had many successes since. And like I said orevioudlybthe idea is these are just 3 F9’s
Indeed no doubt they learned from THAT. Undoubtedly, one of the things they learned is that there are many more "thats" which they don't know about, and every time you change something, and even if you don't, those "thats" can creep up on you.
Remember, there are millions of things that can happen to a rocket, and only one of them is good.
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As Steel said, g is 9.81, and NOT the gravitational constant.
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11 minutes ago, GoSlash27 said:
I'm curious as to why they chose the exact same 2nd stage engine for the Heavy as they use in the 9. An engine that circs 25 tonnes is also capable of 70 tonnes? If that's the case, isn't that engine kind of overkill for the Falcon 9?
Best,
-SlashySo that they don't have to develop/ tool/ build/ support a completely different engine for what is used in 10% (or, in this case, 3%) of the rocket.
Commonality of parts is a big theme at Space X, because it creates huge cost and headache savings. It's at the cost of a bit of payload, but apparently that is something they can spare.
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Your orbit would degrade and you would sink into the lower atmosphere (or at least parts of you). The problem is that once you hit enough atmosphere, your trajectory quickly degrades and puts you into a steep path to the denser parts...but, much steeper and hence quicker than you want to give you enough time to shed your speed and heat. The result is that you DON'T shed enough speed and heat and you either burn up or break up, or some combination of both.
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It highlights the fact that it IS used, they are confident that it will fly, and they plan to do it again. Often, quickly, and cheaply.
Such that they don't even bother cleaning it.
You know when you go check out a used car and it's been so well cleaned that it's suspicious? I think it's kind of like that.
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It is possible to be pushed, purely mechanically, purely by wind, directly downwind, to a speed greater than said wind.
It's not as succinct, but since we're being pedantic
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4 hours ago, Green Baron said:
Simple answer: no. (Edit: or you're cheating with the engine)
It is theoretically possible, because the wind can contain more than enough energy that the craft needs to travel at or above its speed. Practically harnessing that energy is a different matter...
...but also possible, and by purely mechanical means:
https://en.wikipedia.org/wiki/Blackbird_(land_yacht)
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It is possible to sail directly downwind, faster than the wind.
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If you lined up all of Earth's viruses end-to-end, they would create a column ~200 million light years long.
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I find that if you want the most delta-v efficient vehicle, a LOT of TWR is good, with the limiting factor generally being 1) can you fit enough engines 2) can the craft handle the heating. Gravity losses are generally much greater than aero losses.
My best EVE ascent vehicle, for example, has something between 2/3:1 TWR on the first stage, if I remember correctly. Any less and it wouldn't perform as well, despite the large dead-weight reduction and theoretically higher delta-v.
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My understanding is that losses due to gravity are much greater than aerodynamic losses, so it generally does make sense to punch it as hard as you can as low as you can.
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10 hours ago, sevenperforce said:
....this means the horizontal component of velocity is roughly 1.27 km/s. However, Cape Canaveral is comoving underneath at a nice steady clip of 409 m/s, meaning that the Falcon 9 first stage only needs to kill about 860 m/s of downrange velocity to essentially "stop".
You lost me...how/ why is the cape moving slower than the rocket?
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48 minutes ago, KSK said:
From the video, speed at MECO is 5877 km/hour or 1.63 Km/s. I'm not sure how much delta-V the boostback burn does impart but I think your estimate is probably a bit high. A 1.5 km/s burn would be nearly enough to stop the whole stage dead in mid air!
I crudely timed how fast the altitude was changing, which gave me the vertical component. From this I figured out the horizontal (~1.1 km/s). In order to kill the horizontal and then hope to make it back, I guessed ~1.5 km/s would suffice.
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I still don't understand exactly what kind of trajectory the rocket flies and how it turns around to the launch site, even after watching the entire video from start to finish. How far down-range does it actually go before turning around?
The speed indicator doesn't seem to help. How much delta-v does the boost-back burn actually take up? It's still going thousands of km/h after the burn, but apparently the other way?
Edit: I did some rough calculations, and I'm guessing it needs 1-1.5 km/s delta-v. Still, would be nice to get more detailed data regarding the velocity vectors and distance.
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1 hour ago, Steel said:
Or, if we assume this was done by professional engineers rather than monkeys, maybe it could suggest that they've extensively simulated and tested these new grid fins and have updated the software with new parameters?
Undoubtedly. But there's no way in hell that's the full story. My point is that it works on a closed-loop feedback control. It moves the grid fins, checks how the rocket reacts, and then moves them some more until the rocket reacts the way that it should.
Okay, so it's a bit obvious now that I said it, but it's just something I never thought about
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5 hours ago, sevenperforce said:
Whoa, really freaking cool:
The new Block V titanium grid fins are curved. They're also substantially larger than the original aluminum ones.
Interesting. I thought that the computer would know more or less how the rocket will react when it tilts and twists the grid fins. But, here it looks like they just came in and slapped on some bigger & curvier fins and they still expect the rocket to return no problem. I guess it implies that the computer basically learns how to control the rocket on the fly. It makes sense; so many variables are always changing. I wonder if, for example, half a grid fin got ripped off, would the computer be able to adjust for it?
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http://spacexstats.xyz/#NextLaunch
Seems not everybody knows about this link.
SpaceX Discussion Thread
in Science & Spaceflight
Posted
There's that, but there's also the sudden need for stairs and things like that. I don't know how much space that would take, but I imagine it's a lot.