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Comment: Re:The Orion is totally over designed .. (Score 2) 37

by DerekLyons (#48196511) Attached to: A Look At Orion's Launch Abort System

No, that would NOT be much simpler and safer. There's a reason why every orbital space plane has been side-stacked (Shuttle, Buran, X-37).

X-37 is top stacked as was the X-23. On the other hand, both are small enough that they could be encapsulated in a shroud to avoid aerodynamic issues. (And you forgot the X-20 Dyna-Soar, which was also top stacked but was not encapsulated.)

Comment: If only it were that simple... (Score 1) 37

by DerekLyons (#48196413) Attached to: A Look At Orion's Launch Abort System

What would have saved Challenger was the first "all-the-way-down" human decision turtle: 15% higher cost for one-piece SRBs instead of the 4-piece propellant sections.

If only the decision was that simple... Sadly, it wasn't.

First there were performance issues; The solid motors need to match to within 5% of each other - which proved essentially impossible to achieve with a monolithic grain as the propellant tended to stratify during the extended pour and the extended curing time. The solid motors needed to have consistent and predictable performance during the burn - which was almost impossible to achieve due to the aforementioned stratification problems. Both problems were also made worse because they couldn't figure out how to safely mix and pour the grains for both boosters in a single batch. Segmented grains, which could be poured in LH and RH segments from a single (smaller) batch suffered from none of these problems.

Next, there's storage and handling problems. The larger the grain, the heavier it is, and the harder it is to prevent it from flowing and deforming under it's own weight. Equally, since the large grains have to be cast upside down they have to be rotated rightside up - and nobody knew how to do that with large monolithic grains. A flex of as little as a couple of millimeters could crack the grain or lead to delamination. Also, segments could be stored individually, reducing fire and explosion risk.

Inspecting the grains with the technology of the time was also several orders of magnitude harder for a large monolithic grain.

Lastly, while there was a only a limited base of flight experience with large segmented grains (via the Titan IIIC)... there was no flight experience with large monolithic grains.

tl;dr version - there were a lot fewer known unknowns with segmented solids than with monolithic solids. A number of the known unknowns for monolithic grains were either outright show stoppers or could result in ruinously expensive R&D programs to discover if a solution was even possible. The known unknowns for segmented grains were all issues of scaling from existing experience.

Comment: Re:This is why NASA sucks (Score 2) 37

by DerekLyons (#48193697) Attached to: A Look At Orion's Launch Abort System

Why on earth or space would you design an escape system like this?

Because it's solid fueled and thus much more reliable than liquids and, depending on design details, much faster to react. Also, it's pretty easy to build in a passive attitude control system that arcs the capsule out of the booster's path while the Draco will require active differential throttling. (Which in the case of Orion also increases reliability, as the launch abort system doesn't depend on guidance being available.)
 

I believe that this must be disposed of on every flight

Which also means it isn't carried to orbit and poses no further risk to the crew or mission. It also reduces total landed weight, reducing the size of the parachutes required and/or reducing landing shock for the same size parachutes.
 

and the separation is not without risk

Nothing is without risk - and Draco has a number of risks inherent in it's higher parts count and more complex operation that the Orion launch abort system does not have.
 
There are advantages and disadvantages to both approaches. Neither NASA nor Musk has the absolute One Best Design - because there isn't any such thing. (And both of them are leaps and bounds above the complex horror that is Soyuz's launch abort system. Sure, it worked when called on... but that doesn't change the nature of the beast.)

Comment: Re:Would this kind of system have saved Challenger (Score 1, Interesting) 37

by DerekLyons (#48193431) Attached to: A Look At Orion's Launch Abort System

Provided, off course, that they hadn't mounted the payload NEXT to the exploding external fuel tank... yes, I know doing it that way let you have lighter structure, but it introduced a whole range of problems and failure modes you wouldn't have had if the orbiter had been mounted on top.

Mounting the orbiter on top has it's drawbacks too... The orbiter's wings now act a lot more like fins, making it harder to maneuver during the early part of the ascent and inducing (very) high structural loads on the stack. And of course the wings are generating lift... right at the part of the stack where they have a nice long lever arm. In addition, if you screw up the stack's angle of attack, you can end up with the wings at an undesirable angle to the apparent wind. (Undesirable in this case means "the wings are trying to turn the vehicle but not the stack", I.E. tearing the vehicle off the top of the stack.)

Comment: Re:Would this kind of system have saved Challenger (Score 5, Interesting) 37

by DerekLyons (#48192917) Attached to: A Look At Orion's Launch Abort System

Second, the boosters cannot be shut off. That's the big safety drawback of solid rockets - you light them, and they aren't going out until they're out of fuel.

*sigh* This is one of the biggest pieces of misinformation about solid rockets floating about out there, spread and repeated by shuttle detractors in a cargo cult like fashion until it's now regarded as a law of nature. What most people (including engineers who should know better) don't realize is that you don't need to shut them down in the first place- you just need them to produce net zero thrust. This is done via blowout panels in the front dome, and sometimes by blowing off the nozzle as well. And it's not like this is a new fangled technique either... It was used on the Polaris A-1 and A-2, Poseidon C-3, SUBROC, ASROC, Minuteman I and -II, and Peacekeeper missiles. It would have been used of the SRB's of the Titan IIIC booster for manned Dyna-Soar and MOL launches. It's used by Minuteman III missiles...
 
It wasn't used by the Shuttle because during the SRB burn, the SRB's are essentially 'dragging' the ET behind it... and thrust termination would have resulted in them 'hanging' from the ET or having to be jettisoned and the resulting changes in structural loads would have shredded the ET and tossed the Orbiter into the airstream where it would be broken up. (Which is essentially what happened to Challenger.) A normal SRB jettison doesn't shred the ET, because the loads come off gradually as SRB thrust decays and they're jettisoned as the T/W ratio passes through 1.
 
NASA looked at using an Orbiter mounted solid rocket to power it away from the stack, but even if the motor was used on a normal flight for orbital insertion after ET jettison it was too heavy.
 
 

Third, the Main engines are nearly useless in-atmosphere. They're lit mainly because they sometimes fail to light, and having that failure occur halfway to orbit would suck. The "boosters" provide about 80% of the thrust, if memory serves. The SSMEs aren't even at full throttle for much of the flight - Challenger had just set them to full when the stack exploded.

A friend of mine, an aerospace engineer by trade, once explained it thusly - "during first stage flight, the SRB's lift the ET and the SSME's lift the orbiter". This isn't entirely true, but it's a useful first approximation. And that being said, other than a brief time right around Max-Q (when the throttles are backed off to control aerodynamic loads) and as MECO approaches (when the throttles are backed off to control G loads) the engines are in fact run at full throttle during powered flight.

Comment: Re:Finally ... (Score 2) 471

by hairyfeet (#48191347) Attached to: Debian's Systemd Adoption Inspires Threat of Fork

Well if the rumors are true then RH has been quietly stacking the deck by loading Debian with ex RH employees then a fork is the only possible chance of keeping from getting system'd.

In case anybody wonders why they are trying to ram systemd so hard? Cloud computing, they want systemd to be a "one size fits all" for their cloud computing initiative. Great for RH, not so great for everybody else. In any case it will be interesting if the users can "take the OS back" from Red Hat and the corporate interests like Windows users did when they refused to take Win 8, it will be quite fascinating to see whether Linux users without the power of the wallet can change things simply by protest.

I personally wish them nothing but luck, as it sucks to see an OS you have serious time and money invested in get a big old shit taken on it by the suits...good luck Debian users, may you tell the suits where they can stick their system'd crap.

Comment: Re:Yes, worse (Score 1) 306

by hairyfeet (#48184067) Attached to: If You're Connected, Apple Collects Your Data

I would only add there is a legitimate REASON for it in an ALPHA BUILD, its so that MSFT can find out which ones of the literally tens of millions of software programs that run on Windows need shims,compatibility modes, or be outright blocked for being incompatible. there is no way in hell even a company the size of MSFT can test THAT many programs so they let us try it before it comes out (which benefits guys like me who can see if our customers would be able to use it) and in return you do just as I've done and let 'em find out which programs don't work and give 'em feedback. They tell you exactly what they are doing ahead of time and again it costs you NOTHING to install this OS and try it on as many boxes as you want.

With Apple the cheapest unit is...what $600 for the Mini? And most have Macbooks which start at like a grand...and they are gonna datamine your ass on TOP of the insane amount of profit margin they are making on their hardware? really? There is greedy and there is fucking greedy piggies, it sounds like we have a case of the latter here folks. I wish this surprised me but sadly it don't, I have customers that were hardcore Macbook users and I've seen Applecare go from "If we built it we service it" to "Oh that an older model we don't fix those...wanna buy a new one?" so this really doesn't surprise me, should have known with Cook starting out in supply that quality would go down while monetizing would go up.

Comment: Re:are the debian support forums down? (Score 0) 281

by hairyfeet (#48178735) Attached to: Ask Slashdot: Stop PulseAudio From Changing Sound Settings?
Interesting? Just for stringing together memes? Well lets break down his meme spewing shall we? We have living in the past, a very old classic and fav of Pogson, we have the ever popular works for me, and of course blaming the user which brings up its free so you can't complain. Oh and I fucking LMAO that the VERY FIRST POST was the ever hilarious battle cry of the FOSSie masses, the ever popular why do you hate free software, because if you don't slurp every drop of koolaid, including that shoved by an employee of the company trying to jam an SVCHOSTS into Linux for its own gain why you MUST be part of an organized attack on FOSS...ROFLcopter the amount of crazy is just too much LOL!

Comment: Re:Glad society is stable for that long (Score 1) 217

by Waffle Iron (#48172115) Attached to: Fusion and Fission/LFTR: Let's Do Both, Smartly

Second, people can read signs even after revolutions. If you put "severe radiation, stay out" on a concrete building, it'll be fine.

An additional advantage to those signs is that in a dystopian future, the terrorists are usually the good guys. The info will help direct those good guys to where they can find materials helpful in the fight against evil governments.

Comment: Re:Baby steps (Score 1) 348

Step 1: research on the ISS focused on biosphere components and food production.

Those aren't baby steps - your step 1 is no lower than about step 5 in any rational plan. We don't even know how to build a biosphere _on the ground_. Baby steps start with the basics, not three quarters of the way up the curve in the most expensive place to perform research.
 

At the same time, work on high efficiency, low reaction mass propulsion systems.

We already have those. The problem is, they absolutely suck because high efficiency and low reaction mass means absurdly low thrust. (F=MA after all.) Absent new physics, that's not going to change and such drives are going to be useless for manned expansion.

Comment: Re:hubris (Score 1) 419

by Tom (#48162013) Attached to: Texas Health Worker Tests Positive For Ebola

But the fact that you used that slur will be used against you by your competition in the campaign. Duh.

I'm not afraid of that. Media and opponents will find something to use against you anyways, and if they don't, they will make it up.

And your apparent deviant character as demonstrated by your racist bigotry online will be used to help convict you.

I pity you for the country you live in. Or maybe I'm just idealistic and believe that whether or not I committed the crime I'm accused of will be used to judge me.

Since you're on the level of ad-hominem attacks now, with no discernable actual content, I'll leave it at that.

Comment: Re:ancient news (Score 1) 87

by jc42 (#48161417) Attached to: Early Childhood Neglect Associated With Altered Brain Structure, ADHD

Decades ago there was an experiment with monkeys deprived of maternal support to varying degrees. Some not allowed to touch or see the mother. Autopsies showed that the deprived monkeys had massive (and obvious to any observer) brain deficiencies. These monkeys were never able to adjust to social settings with others of their kind. Their behavior was obviously abnormal. My impression was that every moment of their life was stressful for them. Sorry I can't recall the source of the video I saw.

This result would be the same for dogs, cats and humans. I can't comprehend why it would be news in the year 2014.

Hmmm ... You seem to have missed the even more "interesting" followup studies. I was a grad student working with some of those reasearchers, so I heard a bit about it. They took their adult solo-raised monkeys, who were highly asocial, and caged them for a while with infant monkeys. After a few months, they took those individuals and put them in the "social" cages with established groups of their own species -- and they behaved like normal, socialized monkeys.

So maybe we could try this with our "deprived" human children. Put them into a social setting (perhaps schools) with younger children, and watch their interactions. They aren't monkeys, of course, but we are all close relatives, so maybe it would work with them, and they'd become at least somewhat better-socialized humans after a while.

Or maybe humans are hopeless. We don't really know until we do such experiments on ourselves. But we do seem to have a population of good test subjects, and the results couldn't be much worse than what we've been doing. Imprisoning such young adults in response to minor mischief would seem to be exactly the wrong thing to do, if those monkey experiments apply to our species, too.

Comment: Re:WMDs? Chemical weapons? Wait, what? (Score 2) 376

by DG (#48158663) Attached to: Pentagon Reportedly Hushed Up Chemical Weapons Finds In Iraq

I doubt I'll have much success in this, but I've tilted and windmills before:

Chemical Weapons are indeed "Weapons of Mass Destruction" - and the key characteristic that makes them so is *indescrimination*.

A straight-up HE bomb (or even a pie-in-the-sky KE weapon) has a known blast radius around its intended target. Pick target, apply Circular Error Probable, apply blast radius, and you now have a circle that pretty accurately defines the amount of damage that weapon will do.

With a Chemical, Nuclear, or Biological weapon, that calculation no longer applies. With each, you get a cloud of contamination whose extent and direction you cannot predict, and - as the contamination is persistant to some degree - you cannot predict the number of unintended exposures to weapon effects after the fact.

A single machine gun, or even a knife, given enough persistance and patience, can indeed kill as many people as any CBRN strike. But unlike the CBRN strike, each person killed will have been done so purpously and with intent - and in the occasion of unintended casualties, those numbers will be small. Not so with a CBRN strike on a military target outside a city, when the wind changes and accidentally contaminates a major populated area..

It is that capability to expose large numbers of non-combatants to weapons effects *indescriminately* from actual combatants that makes these "WMDs"

Comment: Re:hubris (Score 1) 419

by Tom (#48157407) Attached to: Texas Health Worker Tests Positive For Ebola

You're not a luminary shining light on the true inner workings of human minds,

I'm not? Now you confuse me. :-)

Maybe I'm influenced by being a European, so I don't have this history of living-memory slavery of black people and so the word is not such a trigger. But that's not the point. I didn't intend or claim to read peoples minds, but let's be honest here: If the Ebola outbreak were in Italy, the worlds reaction would be quite different. There is a definite element of racism involved in how we treat the matter, including the often made "let's just stop all travel" argument.

I don't care enough to try and dox you, but thanks for giving public permission to anybody who might. If what you say is true and you ever decide to run for public office, you're accused of a serious crime, you go through family court litigation, or you face any other circumstance whereby others have incentive to put your character under scrutiny, then God help you.

You're a bit strange. If you run for office, your private address will be public record almost immediately. Your family can be assumed to know where you live. If you're accused of a serious crime, you're going to be in jail, so it doesn't matter. So whatever point you were trying to make, I'm afraid your rage blurred your rationality.

HOLY MACRO!

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