SpaceX News

Point out news stories, on the net or in mainstream media, related to polywell fusion.

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GIThruster
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Re: SpaceX News

Post by GIThruster »

Next landing attempt today at ~4:42 PM Eastern

http://www.spacex.com/webcast/
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

Maui
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Re: SpaceX News

Post by Maui »

Showers/storms look to be surrounding/closing in on the cape. The Jaws theme would be an appropriate soundtrack to the radar screen right now...

jcoady
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Re: SpaceX News

Post by jcoady »

From the live Port Canaveral webcam, the skies look clear.

http://www.portcanaveralwebcam.com/

GIThruster
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Re: SpaceX News

Post by GIThruster »

Launch is scrubbed today for weather. Next launch opportunity is tomorrow 4/14 at 4:10pm EDT.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

ladajo
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Re: SpaceX News

Post by ladajo »

<Sad Face>

New launch at 4:10ish tomorrow (Tuesday).
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

kunkmiester
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Re: SpaceX News

Post by kunkmiester »

So, uneducated opinion, how far can they desensitize rocket from weather? I know rockets are more sensitive than airplanes or helicopters to low altitude winds, more so when you're also trying to land them, but you're going to get three things: customers who don't quite get that and get upset at delays no one else deals with, personnel scheduling issues, and lost launch windows.

There probably won't be much done to try to work on that (however much can be done) until it starts causing problems, but it's worth thinking about.
Evil is evil, no matter how small

Maui
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Location: Madison, WI

Re: SpaceX News

Post by Maui »

Fairly uneducated myself, but I think aircraft are obviously much better equipped to make control corrections due to wind and also not prone to dealing with the same shifts in wind that occur when traveling vertically at super-sonic speeds.

As for lighting, IIRC there are things that could be done to make the vehicles more robust, but it would cost performance. That's combined with the fact that delays of a few days for orbital payloads generally aren't that big of deal (vs a huge deal for passenger planes).

Recently saw this map of lighting frequency across the globe-- it looks like the Brownsville spaceport should may be a much more effective a avoiding lightning delays than a more robust rocket would be anyway.

GIThruster
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Re: SpaceX News

Post by GIThruster »

IIRC, 93143 posted an analysis some months back in this thread of how wind affects rockets not only during launch but in the landing phase which is even more critical I think. It is non trivial, the forces that can be exerted both by cross winds, and also rain striking the launch vehicle supersonic. So weather is something you need to work around at times. I think by the time a launch vehicle clears the tops of clouds that bear ice, it is moving mach 3 or 4? and ice striking a craft at that speed could do more than cosmetic damage, especially now when you have these fins and legs attached with moving parts and hinges. Think of the energy in a hailstone striking something at Mach 3 and really, they're like bullets in some ways.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

GIThruster
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Re: SpaceX News

Post by GIThruster »

Almost!
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

Maui
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Re: SpaceX News

Post by Maui »

But at least we get another entertaining video out of the deal:
https://vine.co/v/euEpIVegiIx
https://twitter.com/elonmusk/status/588146703938756608

EDIT: Looks like Elon retracted his promise of HD pics/vids.

birchoff
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Re: SpaceX News

Post by birchoff »

Maui wrote:But at least we get another entertaining video out of the deal:
https://vine.co/v/euEpIVegiIx
https://twitter.com/elonmusk/status/588146703938756608

EDIT: Looks like Elon retracted his promise of HD pics/vids.
ummm... the promise I saw say that the HD pics/vids would have to wait till the barge got back to port. the vine video looks like it was shot from an arial drone or someone not on the barge.

kunkmiester
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Re: SpaceX News

Post by kunkmiester »

Have hey been able to save anything from these botched landings or is the whole thing just going straight overboard? Be interesting if they were getting at least a little bit of data from it.
Evil is evil, no matter how small

DeltaV
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Re: SpaceX News

Post by DeltaV »

My first guess(es) on what happened:

Two or three of the control loops (altitude rate, angle from vertical and lateral-position-driven lateral velocity) stepping on each other's toes, maybe with an ill-timed wind gust near the end.

The altitude rate and the vertical angle control looked too under/over responsive, respectively. Lateral velocity looked better.

Alternately, sort of an inverse of the above: vertical angle control trying to deal with an over-aggressive lateral velocity loop, but having less authority. (There is a psychological incentive to hit the bullseye).

Maybe just constants tuning needed, maybe more.

In either case, the high h_dot is kinda surprising. Would a few more seconds of burn time add that much weight?

This is assuming no sensor/thrust/TVC/... failures occurred.


DeltaV
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Re: SpaceX News

Post by DeltaV »

DeltaV wrote:In either case, the high h_dot is kinda surprising. Would a few more seconds of burn time add that much weight?
Upon further review, even one Merlin gives T/W > 1, hence the "hover-slam", by design. But h_dot magnitude near the pad should still be reduced, if possible, to give the other loops more time to deal with excursions.

So it was stiction-caused phase-lag wrt fuel/ox. That would explain the under-responsive altitude rate control. Yielding more slam and less hover.

It looked like phase-lag, but I wanted to be continuously discrete and not make wavelets.

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