Posts by Mike Hewson

11) Message boards : Cafe Einstein : SpaceX Dragon scheduled for 12/19 (Message 140281)
Posted 4 days ago by Profile Mike Hewson
Darn. But they will get it down safe one day ....

Cheers, Mike.
12) Message boards : Cafe Einstein : SpaceX Dragon scheduled for 12/19 (Message 140279)
Posted 4 days ago by Profile Mike Hewson
There's a snap here of the 1st stage at the barge.

Cheers, Mike.
13) Message boards : Cafe Einstein : SpaceX Dragon scheduled for 12/19 (Message 140275)
Posted 4 days ago by Profile Mike Hewson
Faultless launch, very impressive.

Cheers, Mike.
14) Message boards : Cafe Einstein : SpaceX Dragon scheduled for 12/19 (Message 140263)
Posted 4 days ago by Profile Mike Hewson
The barge has got "Just read the instructions" written on it. LOL! Elon is my kind of guy .... :-)

Cheers, Mike.
15) Message boards : Cafe Einstein : SpaceX Dragon scheduled for 12/19 (Message 140254)
Posted 4 days ago by Profile Mike Hewson
But some motions were oddly jerky (for example, when the things which looked like clamps opened away form the vehicle).


I noticed that also. My initial response was that the "left" clamp was not moving and stuck in place (big problem), but after the right one moved away from the vehicle then the left one moved.

Do you mean the claw/clamps up at the top of the gantry before it leans back ? The ones that grip the payload ?

If so then the one on the right with the usual camera view ( so actually the left sided one if you are looking at the rocket from the gantry ) has been going first in all the launches I have seen, and after about at least five seconds the other side then retracts. Both seem to jerk and wobble slightly several times during the retraction arc, as if the hinge is momentarily stuck and then suddenly releases.

Cheers, Mike.

( edit ) Apropos of nothing in particular : I've been researching the Minutemen missiles. These are solid fueled. They need to shut off very reliably to the instant in order to ballistically progress to target with high accuracy. But how do you throttle a solid fuel firecracker once lit ? Won't it burn until fuel exhausted ? Loading a fixed amount of fuel prohibits re-targeting.

The solution was brilliant and simple. At the predetermined moment, some bolts blow on vent covers up at the head end of the missile. The air rushing in at that Mach 20+ speed just blows the flame out ! Even if not, then any lingering combustion has no sealed surrounds to recoil against and thus produce forward thrust. Thus little or no pressure in the reaction chamber and so no go. Very clever and so obvious in retrospect. :-)

( edit ) Here is a genuinely spooky scenario from the Mutual Assured Destruction tactical cabinet. This was considered in the early 60's by US analysts before submarine launched & cruise missiles etc.

Suppose the Russians using some of their land based silo nukes did a pre-emptive strike on US continental silos. US satellites note in early flight which Russian silos were launched from and thus which still retain unsent salvos. The US waits until it is clear which of their silos are being descended upon. So by then the Russian missiles are in late stage of their journey indeed. When it is quite apparent to the US which silos will be shortly nuked, they launch from those silos alone, but only targeting the Russian ones as yet un-launched from.

The proposed nett effect of the exchange ( all going 'well' ) is that the USSR missiles were wasted hitting the recently vacated US silos, and the US missiles devastate any remaining unused USSR ones sitting in their holes. And the US still has very many nukes in hand. So this is scored as a credible US 'win'. All happening within about 3/4 of an hour. In reality it would require amazing timing finesse to succeed, with probably less than four minutes to re-target and launch hundreds of missiles. These retaliatory missiles would likely just pass say, 50,000 feet going upwards, when their silos get obliterated below them.

It boggles me to think that this type of 'logic' was entertained and in a upbeat manner as it were. When I was a mere toddler. It's a good thing we never found out if it would have worked.
16) Message boards : Cafe Einstein : SpaceX Dragon scheduled for 12/19 (Message 140247)
Posted 5 days ago by Profile Mike Hewson
I couldn't get on to the feed at all. :-(

When I first tried after robl posted it and advised there should be a count down clock, I saw the clock in some browsers, but not others. You might try another browser next time, Mike. Or not living down unda, or ...

... not living on the edge of the local node's broadband reach ie. 4.5 km from the DSLAM port on 60+ year old twisted pair. They had to remove an inductive/HF choke from 1952 just to get a handshake. On a good day my service is rated at 4 ( out of 24 whatevers ). FWIW my daughter actually works for the ISP and got a techie gadget to have a special look/test. She just rolled her eyes ..... some form of aggressive quantum tunneling was my only remaining option* alas. :-)

If the price of copper goes up just another 10% it will be worthwhile to dig the line up myself ..... thus paying for a two-way sat link. :-)

Cheers, Mike.

* Or possibly some quantum effect has already been leveraged to achieve the 4 ...

( edit ) With the pretty good price of copper nowadays there has been more than a few instances of 'infrastructure theft' around and about. By the time the repair crew gets to some remote site to fix the outage, all they find is a scorched concrete plinth and nearby wheel tracks. One doesn't need much gear that won't be readily re-imbursed : an oxy-cutter, a light truck with a winch and a tarpaulin. Transformers are highly sought after. You need a good thickness of metal bar for grounding to pop the fuses.
17) Message boards : Cafe Einstein : SpaceX Dragon scheduled for 12/19 (Message 140239)
Posted 5 days ago by Profile Mike Hewson
I couldn't get on to the feed at all. :-(

Cheers. Mike.
18) Message boards : Cruncher's Corner : BRP4G WU (Message 140215)
Posted 5 days ago by Profile Mike Hewson
The non-gravity work was engaged for several reasons ( this is multi-year-old news to most regulars but I will repeat for the clarity of others ).

Firstly it was intended to be relevant for the period awaiting the LIGO upgrades now completed ie. give us here at E@H something to do while the advanced interferometers were brought into being. That purpose has been fulfilled. ( Alas the intermediate Enhanced LIGO configuration ( ~ 2010 ) really didn't technically perform well enough for E@H signal searches, regardless of whatever else was learnt during that time ).

Secondly the PALFA group had a need for signal analysis that they couldn't provide. This purpose has definitely been fulfilled, and then some !

Thirdly the astronomical objects of interest - pulsars - are the same target class as those the Continuous Wave Group of LIGO are studying. Especially non-axisymmetric pulsars ( 'bumpy' if you like ) that ought radiate GWs, and such signals are the ones we will soon be trawling the AdLIGO data streams for. We now have a well practised and understood pipeline awaiting this role.

[ The gamma-ray work was later added in with much the same logic. ]

As for permanent and endless crunching, that was and always will be true. There is a vast parameter space out there to explore for any particular data set. This is a simple consequence of the blind search strategy, by definition one is choosing as yet untried signal templates in the hope of gaining matches. This is akin to listening for a bird call that you have never before heard*. I urge you all to interpret this quality as an exciting aspect of the project indeed ! Even if E@H is not the first to detect a GW that doesn't mean any subsequent work we do won't be novel, interesting and/or groundbreaking in it's own right. Far from it. We are on the verge of a really fascinating era of discovery !!! Come on fellow crunchers, get your grins out in anticipation please .... :-) :-)

[ Yes I know. For many of us it has been a long 10 years. As decades tend to be. So it may be hard to rustle up even a wee bit of 'go fever' at this stage. But I try .... :-) ]

As for which 'direction' the searchlight is pointed in parameter space for any given phase of this project, then I trust the overseeing scientists to judge that. Evidently they seem to have an effort vs. reward tension in such decisions. I'd be a fool to attempt a second guess.

Personally I only crunch for E@H, and somewhat mono-manically to boot. I've ticked all the boxes for task type availability, hence my rigs will follow the flavors as determined by project managers. But that's just my ( lazy ) choice. I can't be bothered managing below that level.

Cheers, Mike.

( edit ) IF there is an implicit criticism lying around somewhere along the lines of the initiators of E@H being unable to foresee in detail what the project would be doing 5, 10+ years hence of ~ 2003, THEN I can only say it really sucks to predict the future !! Please stop reading now, go and do something far more fruitful and deterministic with your life/brief-mortal-coil : pick & bet on some winners for your local horse races this weekend coming up. Bleeding edge astrophysical investigation is not for you !! :-)

* In a very bloody noisy forest where you can't see any of them.

( edit ) A few years into my involvement here I remember clearly being heavily struck one day with the realisation of how ambitious it is to attempt the measurement of effects of order 10^[-24]. Thus I cannot understate how amazing it is that both LIGO IFOs have recently demonstrated prolonged lock, and certainly good enough quality for serious analyses, at that design spec. WOW !! :-)
19) Message boards : Cafe Einstein : SpaceX Dragon scheduled for 12/19 (Message 140211)
Posted 5 days ago by Profile Mike Hewson
Thanks for that information Peter. :-)

The SR-71 ( and all along that line however denoted ) have unique engine characteristics.

- fuel is a special high grade kero with a catalyst in the mix. Without the tetraethyl borane not much interesting happens.

- a variable intake spike which modulates the bow shock position for the supersonic external -> subsonic internal transition.

- best efficiency is at the top end of both altitude and speed.

So paradoxically you slow down and go low to refuel which is less efficient than if you'd stayed high. Alas no supersonic refuelers ....

Cheers, Mike.

( edit ) A brief research indicates that the JP-9 fuel used by the SR-71 is quite similiar to that used for the air launched variety of cruise missiles. Methyl cyclohexane seems to be the key stuff here. The main desired property is low melting point ( so it doesn't freeze at high altitude ) and high volatility ( to enable starts/restarts at high altitude/velocity ). You don't really want to come down during a mission if flameout happens. This is a long way in performance and price from your bog standard commercial flight fuels.
20) Message boards : Cafe Einstein : SpaceX Dragon scheduled for 12/19 (Message 140207)
Posted 5 days ago by Profile Mike Hewson
No Magic, that would be 1960 ie. 55 Sun circuits completed ex-womb tomorrow. :-)

Here's some better figures : 80,000 feet, 3572 km/h, two North Korean Mig's disappearing faster than the speed of sound behind you. Now there are 3600 seconds in an hour so that'd be 1000 m/s ...

Cheer, Mike.


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This material is based upon work supported by the National Science Foundation (NSF) under Grants PHY-1104902, PHY-1104617 and PHY-1105572 and by the Max Planck Gesellschaft (MPG). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the investigators and do not necessarily reflect the views of the NSF or the MPG.

Copyright © 2015 Bruce Allen