Archive for the ‘Science’ Category

Karoliina has some thoughts on plane design, looking at High Altitude Long Endurance (HALE) UAV:s as inspiration for high L/D craft, to ultimately cruise at fast speed with little power. I disagree somewhat, and I’m sketching out why, below.
Probably the drones, like sailplanes, want low sinkrate and high L/D is secondary, because they need to just stay aloft and not go anywhere.
Power needed is P = v*D (we assume). Since D = CD*v*v, P = v^3*CD.
Lift is L = CL*v*v so v = (L/CL)^(1/2). (Note this CL is different from the L = 0.5*rho*A*cl*v^2, so CL = 0.5*rho*A*cl. It’s more practical here.)
Power thus is P = v^3 * CD = L^3/2 * CD * CL^-3/2.
The lift equals mass, so the power needed is
  1. proportional to mass^1.5,
  2. proportional to the drag coefficient and
  3. inversely proportional to the lift coefficient^1.5.
This means the lift coefficient CL needs to be large for the craft to be able to loiter for a long time. So long wings and somewhat cambered profiles. A little drag doesn’t hurt as much as low lift so struts are a possibility.
Instead, for a piston cruiser, the L/D needs to be maximized for a certain minimum trip fuel consumption, not per time. Basically, you want to minimize delta_E = P*delta_t = P * delta_x/v so the cost function J = v^2 * CD = L * CD / CL which minimizes at maximum L/D. The CL term is less important compared to the loiterer. As a first guess this should optimize to a less cambered airfoil and smaller or shorter wings. And no struts.

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The fenestron already improved helicopter noise problems a lot (less tail rotor and main rotor interference) but this new blade tip they’re working with at Eurocopter seems like a great advance!

If the power levels / flight situations are the same in the two examples but the difference in the annoyance level of the sound is striking.

Now something similar for airplane propellers!

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I do appreciate that the model is so different from Apollo that it takes time and thought to understand what it is about; I did not see it at first myself — but once I got past my preconceptions, I found the logic of this approach overwhelming. This is simply what exploration looks like in a world where the budget doesn’t double for a few years and then halve again. You build a piece at a time and as soon as you can start doing things with the pieces, you do so.

Jeff Greason about the Flexible Path, commenting on Rand Simberg’s superiorly excellent Popular Mechanics piece.

Rand Simberg in the article:

I would claim that in fact, this is the most visionary space policy that the nation has ever had, including Apollo. It finally, forthrightly declares a national goal of large numbers of humanity living off planet, with many of them going on excursions into the solar system, and it harnesses the vital element of private enterprise and competition to make it happen in a way that will drive costs down instead of up.

May I add that yours truly proposed something of a flexible path of his own in 2006, though only for launching.

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Local is not Global

global temperature anomaly map for January 2010

RSS Satellite Temperature, January 2010 Anomaly

Some people in the blue islets say and have been saying it’s been cold. It has been, locally, in the US, Europe and Siberia. But globally averaged, January 2010 was warm. At least according to this data. They’ll be checking it thoroughly since January only ended a few days ago.

Anyway, it’s one of the beginner fallacies to extrapolate globally from a local (or short time) situation, and it seems to sit very tight even among some engineer friends of mine who should clearly know better. It’s “cold here now hence IPCC is wrong” or some variation thereof, like Peter Sinclair reviewed a year and again a few weeks ago.

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From all places, a libertarian, who is arguing for laymen to trust experts.

Come to think of it, there’s a certain class of rhetoric I’m going to call the “one way hash” argument.


The talking point on one side is just complex enough that  it’s both intelligible—even somewhat intuitive—to the layman and sounds as though it might qualify as some kind of insight. (If it seems too obvious, perhaps paradoxically, we’ll tend to assume everyone on the other side thought of it themselves and had some good reason to reject it.) The rebuttal, by contrast, may require explaining a whole series of preliminary concepts before it’s really possible to explain why the talking point is wrong. So the setup is “snappy, intuitively appealing argument without obvious problems” vs. “rebuttal I probably don’t have time to read, let alone analyze closely.”

Hat tip to Scruffy Dan again for the link.

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Robert Grumbine examines them in many of his recent posts. This might be good for engineers and physicists from other fields trying to get the basics.

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However, the oft quoted the Himalayan glacier may be gone by 2035 is still not a realistic conclusion based on the recent ongoing significant retreat of the many still large Himalayan glaciers.

Glaciologist Mauri Pelto commenting in November 2009. What’s ironic is that the main subject of Nature’s Climate Feedback’s blog post was some random offhand claim of no global warming glacier melt from an Indian geologist that made headlines. And Mauri was complaining why something like that gets the headlines and not real methodically prepared papers.

So why is this non-peer reviewed Himalayan report by another worth commenting upon, when many very important peer reviewed papers on glacier change are ignored? A read of this Ramesh report indicates the widespread and significant glacier retreat. The report also notes that all the glaciers observed have negative mass balance. After observing the significant and widespread retreat and mass loss the author deems it to slow to be due to global warming, without any real analysis of the climate data or what could be causing the loss. This simply does not warrant our attention. However, the oft quoted the Himalayan glacier may be gone by 2035 is still not a realistic conclusion based on the recent ongoing significant retreat of the many still large Himalayan glaciers. Can we stick to covering better material?

He was proven not only doubly but triply right. IPCC, the Indian geologist and the media representative – all three could be observed not holding the ball at that instant in time and subject by the astute commenter. I remember reading that.

There are probably more mistakes in the IPCC reports that are yet to be found, that’s how it is. This one was pretty bad though. Though no matter the exact subject, there will be a gate on every possible subject in rapid succession for months until people are numbed to the whole word. It brings hits. 2035 Gate. Himalayagate. Glaciergate. Pachaurigate. Sad.

Also, William has more on how it is, or could be.

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Richard Rood has a thoughtful piece written up on contrarianism, irrationality and disruption. It seems a bit naive for me but then again I don’t have much of the same experiences…

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A project you can partake here. Rewriting some NASA GISS temperature record code in Python at first.

I’d go further and say things like these should not be volunteer efforts… government codes for something important like this should be open (and GISS is) with people being paid to update and keep them in good shape. Hopefully they can take things like these as templates.

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Hack and get some climate researchers’ emails. Then point to some pretty reasonable stuff as evidence of a conspiracy if taken out of context.

It seems there are a few cases certain people latch onto.

There was a certain lousy paper pushed for publication in the journal called Climate Research. It was crap – the claims in the paper conclusions could not be justified by the data or methods presented in it. It was also written by known fossil industry funded frauds. It went through anyway because of a bad reviewer and editor, and actually was pushed as support for policy. Like pushing creation science somewhere in a weak journal so you can cite it as “peer reviewed”. Many other editors for the journal quit as a result. Read the story here, where “Clare Goodess explains the circumstances behind the resignation of half of the editorial board of the journal Climate Research”.

I do hope for more openness on the data and algorithms front. Of course if you’re a climate researcher and get your data only with personal agreements (from the data collecting scientists and institutions who might work under lots of constraints – these might not be the same people who make models or the temperature reconstructions from the data).

I don’t know about the FOIA (government information) requests… It seems bad that things have been withheld. On the other hand if you get so much FOIA requests just for posturing’s sake from certain people that you’re swamped by them, that’s unreasonable as well.

Then there’s the alleged “trick” to hide some cooling. AFAIK, this is just a known proxy issue where they are in error at some point and thus when you make some plots you don’t use that period but “hide” it.

Quite weird arguments.  The FOI one is the most serious looking to me, and others seem just fake.

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