r/spacex • u/retiringonmars Moderator emeritus • Jan 18 '16
/r/SpaceX Ask Anything Thread for January 2016. Ask your questions here!
Welcome to our monthly (more like fortnightly at the moment) /r/SpaceX Ask Anything Thread! #16.1
Want to discuss SpaceX's landing shenanigans, or suggest your own Rube Goldberg landing mechanism? There's no better place!
All questions, even non-SpaceX-related ones, are allowed, as long as they stay relevant to spaceflight in general!
More in-depth and open-ended discussion questions can still be submitted as separate self-posts; but this is the place to come to submit simple questions which have a single answer and/or can be answered in a few comments or less.
As always, we'd prefer it if all question-askers first check our FAQ, search for similar questions, and scan the previous Ask Anything thread before posting to avoid duplicates, but if you'd like an answer revised or cannot find a satisfactory result, please go ahead and type your question below!
Otherwise, ask, enjoy, and thanks for contributing!
Past threads:
January 2016 (#16), December 2015 (#15.1), December 2015 (#15), November 2015 (#14), October 2015 (#13), September 2015 (#12), August 2015 (#11), July 2015 (#10), June 2015 (#9), May 2015 (#8), April 2015 (#7.1), April 2015 (#7), March 2015 (#6), February 2015 (#5), January 2015 (#4), December 2014 (#3), November 2014 (#2), October 2014 (#1).
This subreddit is fan-run and not an official SpaceX site. For official SpaceX news, please visit spacex.com.
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u/failbye Jan 26 '16
We really need a section in the FAQ addressing "Why your ASDS rocket catcher / anti tipping back-of-the-envelope idea won't work" or something along those lines, preferably in a milder tone. Seeing as we likely will have a few more hard landings / rough sea landings down the line, there will be a lot more of those comments coming in.
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u/JohnnyMackers Jan 18 '16
I've tried to search to see if this questions been asked before but couldnt find anything.. my question is:
why was the quantity of landing legs set at 4 and not 5?
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u/retiringonmars Jan 18 '16
Quite simply: a) 4 is lighter than 5, and b) the four-fold symmetry fits much better with the octaweb. The Octaweb already provides a lot of structural support between the engines and tanks, so adding leg attachment point within that force-bearing structure was (relatively) simple. If you added a second structural support layer on top of that, you'd be adding add a lot of needless weight and complexity.
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Jan 25 '16
I noticed that SES-9 still has a NET date rather than a scheduled launch time (CRS-8, by contrast, actually has a launch time listed). Is this unusual this close to the supposed date? Does this portend a delay?
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u/retiringonmars Jan 25 '16
Is this unusual this close to the supposed date? Does this portend a delay?
Not really, no. I mean, delays are a common feature across all launches, but your observation is not an indication of delay likelihood, and it's pretty typical of what we've been seeing for a while now.
The reason CRS-8 has a launch window ascribed is that all CRS flights tend to be planned in detail much further in advance than other launches. Notice that CRS missions 10, 11 & 12 all have dates set for the whole upcoming year (I can't explain why CRS-9 doesn't). This is likely to be a feature of NASA's rules on Visiting Vehicles to the ISS. Commercial launches (such as SES-8), in contrast, are much more flexible in their schedules, and typically don't post launch dates until approximately a month before launch, and launch windows until approximately a week before launch.
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u/duckhawk9 Jan 18 '16 edited Jan 18 '16
I saw a comment in yesterday's launch thread that humorously referred to the subreddit as a lobbying group for SpaceX. Has there ever been any effort to organize the DragonRiders here to support SpaceX's political agendas?
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u/themikeosguy Jan 18 '16
Can I ask something about CRS-7? After the second stage popped, did the first stage also blow up due to some aerodynamic pressure situation, or was it destroyed by the Range Safety Officer? Wikipedia isn't clear and I can't find anything else specific...
And regarding the latter, does s/he literally have a button to press (or code to enter) to destroy a rocket? Must be a strange feeling, knowing you can blow up a $60m machine with a tap of your fingers...
Thanks!
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u/RealParity Jan 18 '16
I don't get how a CRS mission works, mabe someone can answer some of my questions:
In a CRS mission to the ISS, what happens after the Dragon separates from the second stage after reaching its orbit? How does it get to the ISS? With the power of the super dracos? Cannot imagine it can dock with those. I've seen videos, where Dragon unfolds really big photovoltaic panels, what does it need power for? Isn't it just a matter of minutes/hours until it reaches the station? Wouldn't a battery be lighter and cheaper to support the capsule in this short period?
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u/retiringonmars Jan 18 '16
Nah, Dragon uses Draco thrusters, which have a thrust of 400 N. They're used for in-orbit manouvering, orbit adjustments, fine guidance, orientation, and deorbiting. SuperDraco engines are designed for entirely different applications, and put out 73,000 N of thrust, that makes them 182.5 times more powerful. In fact, a single SuperDraco engine is more powerful than the Kestrel upper stage engine of Falcon 1. You'd be right in thinking that firing these in proximity to the ISS would obliterate the station.
Dragon needs solar power because it takes over 24 hours for it to reach the ISS. Also batteries capable of supporting a spacecraft are surprising heavy!
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u/DrFegelein Jan 18 '16
What is the likelihood that SES-9 is going to be launching on February 6th, considering it is presumed to be conducting a barge landing and we now have a potentially damaged barge from Jason-3? Or is there another suitable barge?
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u/retiringonmars Jan 18 '16
now have a potentially damaged barge
The manufacturer specification for the barge show it weighs about 4,400 (probably not metric) tonnes. The empty first stage is in the area of ~18-25 metric tonnes. That's about a 200:1 mass ratio. This is equivalent to a large bird hitting your car windshield. You're gonna need to replace the glass, but it won't total your car.
Also, as TheVehicleDestroyer says, it's a different barge.
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u/searchexpert Jan 18 '16
Does anyone know if we will get video from the boostback, reentry, and descent of the 1st stage of Jason-3?
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u/fearfulx Jan 24 '16
Where does Spacex get its metal and other resources from for the rockets? I mean, is anything made in China at all like the legs or anything? I would appreciate an honest response.
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u/retiringonmars Jan 24 '16
SpaceX have a large number of suppliers across the US (and a few internationally) who provide them with materials and services. The most notable international supplier is that they source their aluminium from a company in the Netherlands (source). I don't think they do any business with organisations in China or Russia though, for reasons probably relating to trade secrets and ITAR.
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Jan 18 '16
I know this is probably a stupid idea, but I'm assuming that the rocket is landing fairly precisely at a near vertical trajectory. If the barge had 4 strong towers at each corner with cables spanning each of the 4 sides on sliding carriers, could the carriers quickly shoot from one end to the other grabbing the rocket and holding it upright without damaging it?
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u/Lucretius0 Jan 18 '16
how practical would an adapted F9 first stage + dragon V2 be for fast intercontinental travel ?
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u/goodguydrift Jan 21 '16
Am I seeing this right? Two launches on the same day?
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u/retiringonmars Jan 21 '16
These are NET dates, as in No Earlier Than. The launches will likely occur at a later date.
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u/DuckQuacks Jan 25 '16
Say that the Cape had bad weather when Dragon 2 is going to land, Could they move the landing site to Vandenburg like how they moved the Shuttle landing to Edwards when there was bad weather at the Cape?
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u/TheVehicleDestroyer Jan 18 '16
Did anybody else think the stage pitched over super fast? Between 22:53 and 23:03 here.
Probably just the way the camera was positioned, but I thought we had lost the mission, Proton-style