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  #101  
Old 01-20-2016, 11:56 PM
scr4 scr4 is online now
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Originally Posted by Magiver View Post
I thoroughly get the point about launching over civilian areas even if they're remote. But I'm talking about land out west where NOBODY lives. They'll be finding crashed planes out there until the end of time.
The way US space programs operate, the area must be completely evacuated - not even a few scattered ranchers, hikers, ships, etc.

White Sands Missile Range is the largest area in continental US that can be evacuated for a missile or rocket launch. This is where NASA launches sounding rockets (suborbital research rockets) - I've worked on several launches there myself. Every launch involves closing the White Sands National Monument and a few roads, to make sure there is nobody within the possible landing area. But even here, the size of the range limits the altitude and downrange (horizontal distance) that the rockets are allowed to fly. The Falcon-9 1st stage flight path will definitely violate this flight envelope.

Last edited by scr4; 01-20-2016 at 11:58 PM.
  #102  
Old 01-21-2016, 11:20 AM
lazybratsche lazybratsche is offline
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Originally Posted by Magiver View Post
Nice links to the Chinese launch sites.

I thoroughly get the point about launching over civilian areas even if they're remote. But I'm talking about land out west where NOBODY lives. They'll be finding crashed planes out there until the end of time.

As for sea landings I think it would be much cheaper to focus on locking down the rocket than stabilizing the platform. In an era of robotic systems I would think it easier to seek out and latch on to the rocket then to try to control the pitch of the sea.
I guess I didn't directly answer your question. E.g., how much area has to be uninhabited? To do that, you can look at hazard maps for each launch -- these are off-limit areas published by the FAA for each launch, compiled into handy maps by a guy on Reddit. This is the map for the CRS-7 launch, showing the liftoff hazard area in yellow, the first stage splashdown area in red (in case of no landing attempt) and the landing area and barge in blue. The landing barge in this case was 220 miles NE.

For other launches, the landing barge or midpoint of the splashdown hazard area has been 400 miles ENE, 120 miles NE, 500 miles E, and 170 miles S. Future launches will launch with different headings (though most will be similar) and the Falcon Heavy will need to land much further down range.

So let's say we want to put a launch site out west. It needs to have the lowest possible latitude, good weather and accessibility. To simplify matters let's assume that this site will only be used for launches almost due east, since that's how most heavy heavy to geosynchronous orbit and beyond are launched. Conservatively you'd need a strip of completely uninhabited land 400+ miles long and 50+ miles wide. Even in the remotest parts of Arizona, New Mexico, and Texas I don't think there's anywhere like that.

Far less conservatively you'd want (say) 50miles downrange to be completely uninhabited, flight paths that don't pass over any towns or major highways, and a number of uninhabited landing zones 400 miles to the east.

Physically possible? Sure. Politically feasible? I'll let you convince the people of West Texas that they should relocate, or evacuate for every launch. And then, after the inevitable launch failure that rains debris near a small farming town, destroying fields and a few buildings, you can convince Congress that launches should be allowed to continue. And figure out how to economically insure each launch to cover property damage liability, deal with the rain of civil lawsuits, injunctions against future launches...
  #103  
Old 01-21-2016, 06:16 PM
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If the concept of "Cheap and easy access to Space" is to be realized, the rules about overflights will need to be drastically altered.

Every once in a while, an airplane falls down and makes a mess.
Yet we allow them to overfly large cities, even during the takeoff and landing phases, which are the highest risk parts of a flight.

Hell, I remember when the jockeys at Wright-Patt would create sonic booms which broke people's windows (yes, I am ancient).

When the massive fireballs of failed launches become a remote memory, "SpacePorts" will become quite common.

One, Spaceport America (301 S. Foch St., Truth or Consequences, NM 87901) thought it had a winner with Virgin Galactic. They are now looking for more suckers with more money than brains investors with Vision.
  #104  
Old 02-23-2016, 04:56 PM
lazybratsche lazybratsche is offline
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Bump for the next launch: Tomorrow, Feb 24th, SpaceX will be launching the SES-9 communications satellite. Launch window is between 6:45 PM and 8:15 PM EST, with a ~60% chance of favorable weather. SpaceX will live stream this launch here.

For this launch, there will be another barge landing attempt. However, SpaceX will be launching its payload into a higher orbit than originally intended, to help the satellite owner get their satellite into position faster (helping make up for the ~7 month delay following last year's launch failure...) This means the landing will be a lot further down range, 600 km east of Florida, and there will be very little margin for error during the landing burns. Nobody seems confident about a successful landing.

(I'll keep bumping this thread for each launch as long as there's interest.)
  #105  
Old 02-23-2016, 05:14 PM
2gigch1 2gigch1 is offline
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Thanks for the bump and please do.

I have been subscribing to a YouTube weekly space interest broadcast called TMRO (Tomorrow).

Every Saturday they put on an hour long TV program from their apartment discussing the topics of interest to the space community. Worth a watch, and some of their other offerings like Space Pod (a weekly short informational video)

TMRO YouTube Site
  #106  
Old 02-25-2016, 04:50 PM
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Bump and FYI to note that the launch was delayed to today, and is scheduled for 5:47 CST (when this post is about an hour old). Weather is 80% favourable at this time. Link.
  #107  
Old 02-25-2016, 05:10 PM
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Thanks, Fang.
  #108  
Old 02-25-2016, 05:30 PM
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Any cable channels carrying this?
  #109  
Old 02-25-2016, 05:36 PM
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It's not a NASA flight, so it's not on NASA TV unfortunately. I'm not aware of any other channels that stream this kind of stuff.
  #110  
Old 02-25-2016, 05:41 PM
lazybratsche lazybratsche is offline
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If anyone wants even more info, there's a nifty live visualization of a (simulated) trajectory here:

http://www.flightclub.io/world.php?watch=1&code=SES9
  #111  
Old 02-25-2016, 05:44 PM
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I was gonna say you can watch it streaming on spacex.com but it looks like they've scrubbed for the evening. Something came up as an issue at T-1:41

Last edited by Pork Rind; 02-25-2016 at 05:44 PM.
  #112  
Old 02-25-2016, 05:45 PM
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I thought it was just me. I lost the feed at :41
  #113  
Old 02-25-2016, 05:47 PM
lazybratsche lazybratsche is offline
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Mmmyup. They seem to be having trouble with super-chilled liquid oxygen. In another launch with higher margins that might be OK, but for this launch I saw a calculation that showed how a very slight reduction in performance in the Falcon 9 would ultimately end up with the payload reaching its final orbit several days or weeks later.
  #114  
Old 02-25-2016, 05:49 PM
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Sounded like problems with the liquid oxygen subcooling again. This is a new thing with the F9 "Full Thrust", and this particular flight is very performance-sensitive (it's right at the limits of the rocket) so they need every last kelvin of cooling they can achieve. I suspect they didn't get quite the cooling level they wanted. The previous FT rocket was not so performance sensitive and they probably didn't care if they didn't quite hit their target.
  #115  
Old 02-25-2016, 05:52 PM
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<shakes fist at lazybratsche for ninjaing me>

The SES-9 satellite carries an ion engine which puts it in its final orbit, but like all electric thrusters it's very slow. SpaceX made a somewhat last minute flight profile change to give them a few hundred m/s of extra delta-V, cutting their final positioning time substantially, but this obviously demands higher performance from the rocket.
  #116  
Old 02-25-2016, 05:54 PM
lazybratsche lazybratsche is offline
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It's also (comparatively) trivial to fill a tank full of liquid oxygen when it's right at its boiling point. There will be constant boil-off, but that can be easily replaced with more liquid oxygen.

Super-chilling requires some kind of active chilling and recirculating in the rocket, or (what SpaceX seems to be doing) loading the oxygen immediately before the launch so it doesn't have time to warm up.

Last edited by lazybratsche; 02-25-2016 at 05:55 PM.
  #117  
Old 02-27-2016, 11:26 AM
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Just for kicks, there are two landing barges. The Pacific one is named Just Read The Instructions, and the Atlantic one (which I've seen docked at Port Canaveral) is named Of Course I Still Love You.
  #118  
Old 02-28-2016, 06:04 PM
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Another slightly tardy last-minute bump:

Today is the next launch attempt. The first countdown was cancelled at 6:45 when a boat entered the exclusion zone by the launch site. They're now trying to determine whether they can clear the water and make another attempt tonight before the launch window ends around 8:20.
  #119  
Old 02-28-2016, 06:33 PM
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Well, that was... interesting. Launch aborted after main engine ignition. I guess something didn't go quite right with the engine ignition sequence?
  #120  
Old 02-28-2016, 06:54 PM
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Originally Posted by lazybratsche View Post
Super-chilling requires some kind of active chilling and recirculating in the rocket, or (what SpaceX seems to be doing) loading the oxygen immediately before the launch so it doesn't have time to warm up.
Supercooling (producing "densified" LOx) requires rapid loading in the supercooled condition; there is no practical way to cool the oxidizer once loaded into the vehicle, as it would require some kind of heavy heat exchanger with circulating liquid nitrogen that would have to be carried along into launch. LOx densification has been considered for launch vehicles before, especially for single-stage-to-orbit (SSTO) vehicles that are extremely mass sensitive such as the X-33, but from a logistical and launch availability standpoint it is extremely challenging for a number of reasons; not only because it requires rapid loading, but also because the heating and stratification that occurs during the loading sequence can cause loss of densification. The supercooled LOx will vent at a higher rate resulting in oxygen impingement on potentially sensitive components on the vehicle which has to be accounted for, including redistribution the amplified heat transfer from even moderate ground winds (which was one of the major contributors to the failure of the STS-51-L starboard booster).

In other words, LOx densification is an expensive and complex way to eke out a small amount of additional impulse for a given propellant volume. The added complexity and cost is contrary to realizing lower cost and higher launch availability, so SpaceX is presumably betting on being able to make the loading process expedient and reliable but in practice they are running into the same problems that have prevented existing launch vehicle providers from adopting densified propellants.

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  #121  
Old 02-28-2016, 07:11 PM
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Well, that was... interesting. Launch aborted after main engine ignition. I guess something didn't go quite right with the engine ignition sequence?
I was on the "Cape" way back when. Our building was about as close as you could get for a Shuttle launch and still be allowed to be there.

Anyway...we are all on the roof for the launch...somebody has a radio going....3...2...1..main engine ignition....holey shit this is the stuff baby!....white clouds billowing outa the bowels the beast...but wait!....main engine shut down...blah blah blah...giant assed groaning sounds...I'm looking for a place to jump off the roof when parts start flying...good times...
  #122  
Old 02-28-2016, 07:17 PM
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I imagine they have the option of giving up on densified LOX and still getting the satellite into orbit, but giving up on 1st stage recovery? I wonder how many tries they get before they resort to that. (Though it's not clear if the trouble today is related to super-cooling of the LOX)
  #123  
Old 02-28-2016, 07:46 PM
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For the SES-9 launch I don't think SpaceX has an option of skipping propellant densification, at least for the second stage. The reserve impulse to land the first stage on the autonomous "drone ship" is actually quite small (as little as 2% to 3% of the liftoff propellant load, although that translates into more delta-V at the vehicle level because it is the last amount of propellant used) and has no impact on second stage other than the small amount of extra mass from densification. SES-9 is a high geosynch orbit that is just at the ragged edge of the capability of the Falcon 9v1.1 vehicle. Given the pressure for the SES-9 launch--the flight has been delayed five months from the original manifest launch date and is crucial to SES meeting their 2016 revenue forecast--I think SpaceX would forego densification for recovery to make up schedule at this point if it was feasible.

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  #124  
Old 02-29-2016, 05:05 AM
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Densification has some particular advantages for SpaceX, though. If you're trying to eke out a bit more performance, one possibility is to stretch the stage. The F9 FT did this, but there are limits--it already has quite a high aspect ratio and they're about as high as they'd like to be in that regard. Making the stage wider is not an option, not only because of tooling costs but because they've made it a priority for the F9 to be road-transportable, and it's already as wide as it can be there. If you can't go longer or wider, you have to go dense.

Also, subcooling has fewer downsides if you're already focused on pad efficiency. They have other reasons for not hanging out on the pad for hours, and if you can manage that, you don't have to worry so much about the propellant warming up.

Another thing is that densification gives them improved thrust. The F9 was already on the low side as far as acceleration at launch goes (IIRC, around 1.2 gees). Increasing propellant mass without increasing thrust could actually lower overall payload. Some rockets get away with adding high-thrust strap-on boosters, but that's not SpaceX's design philosophy. Subcooled propellant is still at least the same across all stages.

Still, we did see one downside today--some idiot in a boat can always cause a range violation, which almost certainly means a 30+ minute delay, which is apparently long enough for the propellant to warm and trigger an abort. I wonder if they could have two rockets worth of chilled propellant on hand, so that they can drain and refill if necessary.
  #125  
Old 02-29-2016, 01:03 PM
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Densification is not a new thing that SpaceX invented from whole cloth; several other contractors have attempted to develop systems around dense propellants (especially SLH2/LOX propulsion systems) and have found the very modest performance improvement to not be worth the cost and complexity of developing and using such a system. Cryogenic densification has numerous functional issues beyond the limited duration of post-loading launch availability, including thermal stratification which can lead to CTE overstress, water hammer induced shock, increased susceptibility to pogo oscillation, propellant utilization measurement errors, the need to carry additional inert mass in the form of insulation, et cetera. It is the only way to get an increase in total impulse out of a set propellant volume without changing engine performance but it comes with a very significant impact on availability, reliability, and processing effort.

The desire to minimize time on pad is understandable for numerous reasons, but the reality is that there are many uncontrollable environmental, security, and safety considerations that may prevent an expedient launch effort, including sudden increase in ground wind speed or wind shear aloft, lightning conditions, anomalies in the countdown sequence, communication issues, and of course, unauthorized ships or aircraft in the flight hazard zone. "Some idiot in a boat" (or a light aircraft, or a hot air balloon..yes, that has happened) is always going to be a potential issue, and frankly will be an even worse problem in the Brownsville site where SpaceX will have no legal authority to evacuate the downrange hazard zone even in US territorial waters, much less Mexican territorial waters. Launch recycles are also very costly; for Atlas V, a one-day recycle costs around US$500k in direct labor alone not withstanding downrange monitoring costs, refueling costs, et cetera, which probably sum up to well over US$1M per day spent on pad. I don't know how much it costs SpaceX to recycle a vehicle, but even assuming a much lower labor wrap rate it is still likely in the mid-six figures for the all-up cost of a recycle, and also with impacts on their anticipated launch tempo.

I strongly suspect that SpaceX will end up limiting cryogenic densification to only the missions requiring highest performance (and with a price premium as a special service) if not abandoning it entirely.

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  #126  
Old 02-29-2016, 04:51 PM
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Most of the things you've mentioned are design issues, though, which presumably SpaceX has already worked through--it's not an additional cost.

The exposure to delays (winds aloft, range violations, etc.) is a biggie, though. They can improve it by streamlining their pad ops even further, but I don't know how much headroom they have. Currently they start fueling at ~T-30:00 and finish by T-10:00. The remaining time is taken by system checks. Could they improve this to, say 15 minutes total? No idea.

I think you're probably half-right. I doubt they'll abandon densification completely, but will work out a system that allows them to "soft fail" in case they spend too much time on the pad. Lighter payloads will fall back to undensified propellant and SpaceX will just accept the additional probability of a failed stage recovery.

There is an interesting tradeoff here, which is that since most GEO birds these days have ion engines, there is some wiggle room in performance. The satellite operator can evaluate the cost of a few extra months of insertion time and some loss in total lifetime against that of having the bird in orbit now (plus any discounts that SpaceX may choose to apply).

That would depend on SpaceX having a good model for performance as it's affected by pad conditions over time. It seems likely that they have such models but I wonder if they're "in the loop" to the extent that they can influence a go/no-go call.
  #127  
Old 03-04-2016, 01:34 PM
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The next launch attempt is scheduled for today, March 4, at 6:35 EST, when this post is about 4 hours old. Link.
  #128  
Old 03-04-2016, 05:22 PM
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Live feed just kicked in. Not sure if the launch is a go yet or not.

13 minutes to planned launch time.
  #129  
Old 03-04-2016, 05:26 PM
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The mission integration engineer is hot.

Just sayin'
  #130  
Old 03-04-2016, 06:11 PM
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The launch and satellite deployment was successful!

No final word on the landing, though the camera on the barge caught a few frames lit by the descending first stage. As in previous launches, the stream cut out right before the landing, what with everything tending to nudge directional antennas out of alignment...
  #131  
Old 03-04-2016, 06:12 PM
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I like her, too! Lauren Lyons is her name. She's so smiley and friendly!

I am guessing that that first stage did not land on the barge like they were hoping? Seems odd that they haven't been able to confirm that, some thirty minutes later, though.

Last edited by Sarabellum1976; 03-04-2016 at 06:13 PM.
  #132  
Old 03-04-2016, 06:17 PM
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#Falcon9 booster did not survive landing, confirmed by #SpaceX. #SES9

No official confirmation, though. Supposedly they used three engines instead of one for their "hoverslam". They were very fuel-constrained, and maneuvers like this (hoverslam, suicide burn, etc.) are more efficient the more thrust you use. However, even with one engine they had a tiny margin of error, and with three the problem is that much worse.
  #133  
Old 03-04-2016, 06:22 PM
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All this to get a silly GTO?

Damned kids today!
Back in my time, we had all the REAL GTOs we needed!

And we Liked it!, Gol-durn it!
  #134  
Old 03-04-2016, 06:41 PM
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Does anyone know how the first stage and the barge do their "dance"?

I have to believe there is some pitch on the deck ,and there has to be some kind of feedback between the two.
Now, if only the engines were instantaneous and had infinitely adjustable thrust.
And then all you have to do is get the two to agree which side is "top", "left", etc.

When they do get the silly things to mate, I will be impressed.

But, just sitting here and watching a satellite being pushed away from a second stage rocket 150+ Km up over Africa, viewed on a machine that is cheaper than the TV my parents had AND has a larger screen. Using a technology they never ever dreamed of?
Nah, not at all impressive.

I was going to make a comment about clocks in automobiles, but I suspect there are about 5 of us who would understand it.
"We can put a man on the MOON, but we can't get a car clock to work!".

This may be the last time that expression is written.
  #135  
Old 03-04-2016, 06:58 PM
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More official:
Rocket landed hard on the droneship. Didn't expect this one to work (v hot reentry), but next flight has a good chance.

Quote:
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I was going to make a comment about clocks in automobiles, but I suspect there are about 5 of us who would understand it.
"We can put a man on the MOON, but we can't get a car clock to work!".
For better or worse, there's no longer a barrier to entry for software. Which means that if you're only willing to pay the absolute minimum for your software, you'll get minimum quality as well.
  #136  
Old 03-04-2016, 07:19 PM
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...
For better or worse, there's no longer a barrier to entry for software. Which means that if you're only willing to pay the absolute minimum for your software, you'll get minimum quality as well.
I take it you are not one of the 5

I'll wait a bit to see if any of the 5 cares to explain the "car clock" problem.

Hint: no software involved.
  #137  
Old 03-04-2016, 07:32 PM
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Apparently not . I assumed you were talking about the Feb 30 thing.
  #138  
Old 03-05-2016, 12:34 AM
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OK - All five of then had their chance:

The first (built-in at the factory) auto clocks were electric motors - running on 6vDC supplied by a generator.
DC motors vary their RPM with fluctuations of current.

To say that those electrical systems "fluctuated" is a huge understatement.

So: Yes, there was a time when people were on the moon but no car clock in the country could keep time.
Hence:
"We can put a man on the MOON, but we can't get a car clock to work!".
  #139  
Old 03-05-2016, 10:11 AM
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OK - All five of then had their chance:

The first (built-in at the factory) auto clocks were electric motors - running on 6vDC supplied by a generator.
Not by the voltage regulator?
It would have to see voltage when the engine wasn't running.

Last edited by carnivorousplant; 03-05-2016 at 10:12 AM.
  #140  
Old 03-05-2016, 05:55 PM
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The problem was:

Battery - which can vary all by itself
Generator - which varies with speed

I suspect the introduction of 12v and, later, the alternator, got the current MUCH more constant.
But a clock's motor really can't vary in speed AND keep anything resembling accurate time.

The "... and we STILL can't make a car clock" became a standard throw-away line.

7/21/69 saw the first man on the moon. And the 1970 model year cars STILL had crappy clocks.
  #141  
Old 03-05-2016, 07:38 PM
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"We can give everybody a computer that can access all the world's knowledge, has a built-in still and video camera, receives signals from outer space to pinpoint its location anywhere on Earth, makes and receives telephone calls as well as text messages, and fits in your shirt pocket; but we can't even land a rocket on a barge!"
  #142  
Old 03-05-2016, 09:49 PM
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I kind of like it...

Sure as hell beats having to explain "car clock" for friggin' ever...
  #143  
Old 03-05-2016, 10:25 PM
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Quote:
Originally Posted by usedtobe View Post
The problem was:

Battery - which can vary all by itself
Generator - which varies with speed
The clock would get about 12.8 volts when the engine is running, charging the battery, and 12.0v when the engine isn't running.
  #144  
Old 03-05-2016, 10:48 PM
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p.s.: the "car clock" gag predates both 12v AND regulators AND alternators.

See http://watchismo.blogspot.com/2007/0...ard-clock.html

Last edited by usedtobe; 03-05-2016 at 10:49 PM.
  #145  
Old 03-08-2016, 11:20 PM
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Overhead pic of debris on the landing barge.

Punched a pretty good hole in the upper left corner! Not a whole lot of identifiable stuff in the pic, though. Is it the octaweb under the tarp? Seems likely, since that's the strongest part of the vehicle and seems to be the largest surviving piece (other than the flattened skin). I figure they just ran out of fuel. Nevertheless, it's impressive that they yet again managed to hit their ocean target.
  #146  
Old 03-09-2016, 08:59 AM
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In his tweets, Elon Musk calls such events "RUD" - Rapid Unscheduled Disassembly.
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Old 03-09-2016, 10:27 AM
Stranger On A Train Stranger On A Train is online now
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It's an old term, dating back to at least the early days of jet turbines (where it referred to the turbine breaking apart under load and destroying the engine) and later used in rocket engine testing. I've seen the terms "rapid unscheduled disassembly" and "singular non-causal mishap" as euphemisms for catastrophic structural failures and non-reproduceable failures without a defined root cause in documentation going back to the 'Sixties.

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  #148  
Old 03-09-2016, 02:11 PM
ElvisL1ves ElvisL1ves is offline
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In all my years in the jet engine world, I never came across it. Thanks for the background.

It's an engineer's typical wry understatement, like "suboptimal" for "sucks", or "rapid oxidation event" (an actual formal term at one enginemaker) for "titanium fire".
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Old 04-07-2016, 02:06 PM
lazybratsche lazybratsche is offline
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Bump for the next launch:

SpaceX is set to launch their next cargo mission to the ISS. This launch is scheduled for Friday, April 8 at 4:43 PM Eastern time (20:43 UTC), and will be followed by another barge landing attempt for the first stage. By all estimates the first stage should have the capability to return to the landing site. However, current speculation is that SpaceX wants to perfect the barge landing since it will be necessary for many landings in the future.

I haven't seen full details on the payload so far, but presumably it will include the usual mix of supplies and new experiments to be conducted onboard the ISS. Notably, however, it will also include the BEAM inflatable module, as a test bed and proof of concept for future inflatable space stations. While it will be attached to the ISS and inflated, for the most part it will remain isolated in case it fails. If it proves safe it might end up being used for extra interior storage. There was a brief discussion of the module in this thread.

The launch and landing will be streamed by SpaceX.
  #150  
Old 04-08-2016, 01:14 AM
usedtobe usedtobe is offline
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OK, I give - the Falcon-9 is on the pad.
Around the rocket and its gantry are at least 4 towers. They look like antenna towers, but:
See this pic.
What are those horizontal wires doing?
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