Legion vengeance, education, other matters Mail 687 20110810

Mail 687 Wednesday, August 10, 2011

You might find this amusing:

http://www.infowars.com/
cameron-to-step-down-recognize-rioters
-as-legitimate-government-satire/

Meanwhile we continue to break things and kill people in Libya.

Kinetic Strike on Taliban

The military spokesman who announced that they had killed the people that brought the special ops Chinook down said that the F-16 had dropped a "kinetic weapon." Gizmodo has a post speculating what kind of explosive bomb was used. In the comments it was mentioned that this could be a "smart rock," a large piece of concrete or something similar with a smart bomb package attached. This was derided by others, particularly with the claim that there would only be enough energy if it was dropped from orbit.

I figured I’d bring the question to The Man.

The post is here:

http://gizmodo.com/5829575/how-an-f+16-might-have-avenged-the-talibans-helicopter-killing

I’ve read reports that smart rocks had been used to minimize collateral damage in Iraq. I’m assuming the strike was against one of the less than sturdy houses in the remote villages. I don’t think you’d need much to take that out.

I’d love it if you’d weigh in then post a link to what you come up with on Gizmodo.

Joshua Beall

I’d be very pleased if the US had Thor or some other extremely high velocity weapon, but I suspect that all this means is that a very large gravity delivered bomb was used. I doubt this is the last misery Taliban in that general area will experience. I would not care to have those units as displeased with me as Taliban around there are at the moment. Beware the fury of the Legions, indeed.

Education

The problem with education in America is simple and impossible to solve in the short term.

My wife is from Ukraine. After earning her mathematics teacher certification (2 years after she came to America) she went to work in a very good school system here in Texas (Mansfield ISD). As a sub and then a regular teacher, she was told many times, by both students and administrators, that she was the first teacher the students had who made math understandable.

She was asked many times (by other teachers and principals) how her successful techniques could be taught to other teachers. She hesitated to let her feelings be known, but finally told them it couldn’t, because she simply knew math far better and more deeply than the other teachers. Their training was sorely lacking. They could do what they had been taught, but didn’t know the theory behind it all and therefore couldn’t teach it to their students. Before most American teachers could teach math her way, they would have to take a couple of years to learn math to the point where they were truly qualified to teach others. And that is only if they had competent teachers (and she didn’t see any when she was in college here).

The Soviet system my wife grew up in was terrible in too many ways to count, but their educational system taught fundamentals in ways we no longer do. Our daughter came here at the end of the 7th grade and spent the 8th grade learning English (no content classes at all). In the summer before the 9th grade, she passed, using credit by exam, Algebra 1, Geometry, Algebra 2 and Chemistry. She was effectively 3 years ahead of American students in math and science. As the song says, "Sad, but true."

(Personal rant … ignore at will)

We will never have truly competent teachers as long as our educational schools concentrate on teaching teachers how to inculcate "social justice" and "diversity" into the curriculum instead of actual content, knowledge and how to transfer this knowledge to students.

Mike Schmidt

==

NCLB Waivers

Jerry,

I’ve been following the discussion of "half of all children are below average" and the failure of nationalized one-size-fits-all education to deal with that. Did you notice that the White House the other day implicitly acknowledged this failure?

The "No Child Left Behind" law mandates that individual schools produce ever-improving standardized reading and math scores, or face sanctions. (Don’t ask why the feds can sanction individual non-federal schools at all; it’s the usual method of dodging the Tenth Amendment by handing out federal funding like heroin then selectively threatening withdrawal.)

The goal is that by 2014, all schools nationwide shall have achieved 100% passing scores. (Lake Wobegon is going to be crowded!) I’m not clear on how high NCLB "passing" math and reading is, but I suspect it’s nothing that an average kid with decent teachers has much trouble with.

Warning, Political Incorrectness follows… The problem, of course, is that there exist both below-average children, and below-average teachers. (That’s wrist-slap PI.) Further, some schools inevitably end up with above-average concentrations of both below-average children and below-average teachers, because some schools are in neighborhoods where smarter people have been self-selecting out for a long time. (That’s hunt-him-down-and-burn-his-house level PI. All our little angels have equal and infinite potential, and God save anyone who publicly acknowledges all the evidence otherwise.)

NCLB seems to have had some success in improving really disastrously badly staffed and run schools, within the limits of local bureaucratic inertia and teacher’s union resistance to culling their worst. Not surprising, in that if you hit something with a big enough blunt instrument, it will change shape. But there are limits to how far you can force a bureaucracy to improve before they learn to evade instead, as witness the Atlanta teacher-organized cheating scandal.

And alas, this side of the Singularity, a below-average kid remains below average, and this side of Heaven, a bad neighborhood bad. Some schools are always going to lag on those aggregate reading and math scores. Under NCLB strictly applied, they’ll eventually be shut down – whereupon whatever replaces them will be faced with the same concentration of below-average kids. It’s quietly becoming obvious that even the Feds can’t mandate that Wobegon spring up anywhere.

The local education bureaucracies that have been complaining about NCLB actually have something resembling a case. (Their being an important constituency in the 2012 election entirely aside…) The White House just quietly announced that they plan to freely grant local waivers to NCLB reading and math score requirements, as long as the school systems involved demonstrate in some manner that they’re really, really trying.

One can hope that this will allow some worse-off schools to adopt plans more suited to the students they have. One suspects it’ll far more often let the local bureaucrats return to not caring whether they’re compounding the problem with bad teaching, as long as they perform the proper rituals for Washington. And one can be sure the White House won’t try to actually reduce NCLB budgets despite this quiet acknowledgement that it’s an increasingly pointless program.

At which point, remind me why we’re paying for so much Federal education funding again?

I don’t dispute the principle of local control, mind. I’m just more immediately appalled by the huge practical waste of money involved in NCLB – a massively centralized approach that wasn’t efficient in the first place and that’s now obviously falling down the curve of diminishing returns.

sign me

Porkypine

We borrow a lot of money from China to fund the Department of Education. Does it accomplish enough to make all those Deficit Dollars worthwhile? Does anyone care?

taxation and representation

Our country was initiated with the cry, "No taxation without representation!" I wonder if the current financial difficulties could be improved by a policy of "No representation without taxation." Everyone should have a financial stake in the country. With slightly less than 50% of the population now exempt from income taxes, our country is approaching the ability to vote for "beer and circuses". Maybe we could limit the franchise to those who pay income taxes–not very likely. Or, maybe, we could base the representation in the House of Representatives by the percentage of each state which pays income taxes.

Larry

 

No taxation without representation

…has gotten us here. Time to turn it around:

"No representation without taxation!"

You don’t pay taxes, you don’t vote. Simple.

Happy belated birthday!

Stephen

No representation without taxation: only those who pay something in taxes may vote. It has been proposed before. Indeed, for all of the early days of the republic, a forty schilling freehold was a pretty standard requirement for being a voter.

When the people can vote themselves largess from the treasury, and impose taxed they do not pay, those people are rulers: at one time a small aristocracy, but is it different if it’s just numbers?

Freedom is not free, free men are not equal, and equal men are not free.

Hello Dr. Pournelle,

I just posted a review of Birth of Fire on goodreads.com. (And, a similar one on Amazon.)

http://www.goodreads.com/review/show/196226163

It IS a good read. Thanks for re-releasing it.

Cheers,

Clyde Wisham

***"You do not have a right not to be offended in this country. So get over it." — Variously ascribed***

 

why low cost SSTO’s are possible now.

Bob Clark

Robert Clark

Dept. of Mathematics

Widener University

One University Place

Chester, PA 19013 USA

Quite key for why reusable SSTO’s will make manned space travel routine is the small size and low cost they can be produced. A manned SSTO can be produced using [i]currently existing[/i] engines and stages the size of the smallest of the very light, or personal, jets [1], except it would use rocket engines instead of jets, and the entire volume aft of the cockpit would be filled with propellant, i.e., no passenger cabin. So it would have the appearance of a fighter jet.

We’ll base it on the SpaceX Falcon 1 first stage. According to the Falcon 1 Users Guide on p.8 [2], the first stage has a dry mass of 3,000 lbs, 1,360 kg, and a usable propellant mass of 47,380 lbs, 21,540 kg. We need to swap out the low efficiency Merlin engine for a high efficiency engine. However, SpaceX has not released the mass for the Merlin engine. We’ll estimate it from the information here, [3]. From the given T/W ratio and thrust, I’ll take the mass as 650 kg.

We’ll replace it with the RD-0242-HC, [4]. This is a proposed modification to kerosene fuel of an existing hypergolic engine. This type of modification where an engine has been modified to run on a different fuel has been done before so it should be doable [5], [6]. The engine mass is listed as 120 kg. We’ll need two of them to loft the vehicle. So the engine mass is reduced from that of the Merlin engine mass by 410 kg, and the dry mass of the stage is reduced down to 950 kg. Note that the mass ratio now becomes 23.7 to 1.

We need to get the Isp for this case. For a SSTO you want to use altitude compensation. The vacuum Isp of the RD-0242-HC is listed as 312 s. However, this is for first stage use so it’s not optimized for vacuum use. Since the RD-0242-HC is a high performance, i.e., high chamber pressure engine, with altitude compensation it should get similar vacuum Isp as other high performance Russian engines such as the RD-0124 [7] in the range of 360 s. As a point of comparison the Merlin Vacuum is a version of the Merlin 1C optimized for vacuum use with a longer nozzle. This increases its vacuum Isp from 304 s to 342 s [8]. I’ve also been informed by email that engine performance programs such as Propep [9] give the RD-0242-HC an ideal vacuum Isp of 370 s. So a practical vacuum Isp of 360 s should be reachable using altitude compensation.

For the sea level Isp of the RD-0242-HC, again the version of the high performance, high chamber pressure, RD-0124 with a shortened nozzle optimized for sea level operation gets a 331 s Isp. So I’ll take the sea level Isp as this value using altitude compensation that allows optimized performance at all altitudes.

To calculate the delta-V achievable I’ll follow the suggestion of Mitchell Burnside Clapp who spent many years designing and working on SSTO projects including stints with the DC-X and X-33 programs. He argues that you should use the vacuum Isp and just use 30,000 feet per second, about 9,150 m/s, as the required delta-V to orbit for dense propellants [10]. The reason for this is that you can just regard the reduction in Isp at sea level and low altitude as a loss and add onto the required delta-V for orbit this particular loss just like you add on the loss for air drag and gravity loss. Then with a 360 s vacuum Isp we get a delta-V of 360*9.8ln(1 + 21,540/950) = 11,160 m/s. So we can add on payload mass: 360*9.8ln(1+21,540/(950 + 790)) = 9,150 m/s, allowing a payload of 790 kg.

To increase the payload we can use different propellant combinations and use lightweight composites. Dr. Bruce Dunn wrote a report showing the payload that could be delivered using high energy density hydrocarbon fuels other than kerosene [11]. For methylacetylene he gives an ideal vacuum Isp of 391.1 s. High performance engines can get get ca. 97% and above of the ideal Isp so I’ll take the vacuum Isp value as 384 s. Dunn notes that Methyacetylene/LOX when densified by subcooling gets a density slightly above that of kerolox, so I’ll keep the same propellant mass. Then the payload will be 1,120 kg: 384*9.8ln(1 + 21,540/(950 + 1,120)) = 9,160 m/s.

We can get better payload by reducing the stage weight by using lightweight composites. The stage weight aside from the engines is 710 kg. Using composites can reduce the weight of a stage by about 40%. Then adding back on the engine mass this brings the dry mass to 670 kg. So our payload can be 1,400 kg: 384*9.8ln(1 + 21,540/(670 + 1,400)) = 9,160 m/s.

Note this has a very high value for what is now regarded as a key figure of merit for the efficiency of a launch vehicle: the ratio of the payload to the [i]dry mass[/i]. The ratio of the payload to the gross mass is now recognized as not being a good figure of merit for launch vehicles. The reason is that payload mass is being compared then to mostly what makes up only a minor proportion of the cost of a launch vehicle, the cost of propellant. By comparing instead to the dry mass you are comparing to the expensive components of the vehicle, the parts that have to be constructed and tested [12].

This vehicle in fact has the payload to dry mass ratio over 2. Every other launch vehicle I looked at, and possibly every other one that has ever existed, has the ratio going in the other direction, i.e., the dry mass is greater than the payload mass. Often it is much greater. For example for the space shuttle system the dry mass is over 12 times that of the payload mass, undoubtedly contributing to the high cost for the payload delivered.

Because of this high value for this key figure of merit, this vehicle would be useful even as a expendable launcher. However, a SSTO is most useful as a reusable vehicle. This will be envisioned as a vertical take-off vehicle. However, it could use either a winged horizontal landing or a powered vertical landing. This page gives the mass either for wings or propellant for landing as about 10% of the dry, landed mass [13]. It also gives the reentry thermal protection mass as 15% of the landed mass. The landing gear mass is given as 3% of the landed mass here [14]. This gives a total of 28% of the landed mass for reentry/landing systems. With lightweight modern materials quite likely this could be reduced to half that.

If you use the vehicle just for a cargo launcher with cargo left in orbit, then the reentry/landing system mass only has to cover the dry vehicle mass so with lightweight materials perhaps less than 100 kg out of the payload mass has to be taken up by the reentry/landing systems. For a manned launcher with the crew cabin being returned, the reentry/landing systems might amount to 300 kg, leaving 1,100 kg for crew cabin and crew. As a mass estimate for the crew cabin, the single man Mercury capsule only weighed 1,100 kg [15 ]. With modern materials this probably can be reduced to half that.

For the cost, the full two stage Falcon 1 launcher is about $10 million. The engines make up the lion share of the cost for launchers. So probably much less than $5 million just for the 1st stage sans engine. Composites will make this more expensive but probably not much more than twice as expensive. For the engine cost, Russian engines are less expensive than American ones. The RD-180 at 1,000,000 lbs vacuum thrust costs about $10 million [16], and the NK-43 at a 400,000 lbs vacuum thrust costs about $4 million [17]. This is in the range of $10 per pound of vacuum thrust. On that basis we might estimate the cost of the RD-0242-HC of about 30,000 lbs vacuum thrust as $300,000. We need two of them for $600,000.

So we can estimate the cost of the reusable version as significantly less than $10,600,000 without the reentry/landing system costs. These systems added on for reusability at a fraction of the dry mass of the vehicle will likely also add on a fraction on to this cost. Keep in mind also that the majority of the development cost for the two stage Falcon 1 went to development of the engines so in actuality the cost of just the first stage without the engine will be significantly less than half the full $10 million cost of the Falcon 1 launcher. The cost of a single man crew cabin is harder to estimate. It is possible it could cost more than the entire launcher. But it’s likely to be less than a few 10’s of millions of dollars.

REFERENCES.

1.)List of very light jets.

http://en.wikipedia.org/wiki/List_of_very_light_jets

2.)Falcon 1 Users Guide.

http://www.spacex.com/Falcon1UsersGuide.pdf

3.)Merlin (rocket engine)

4 Merlin 1C Engine specifications

http://en.wikipedia.org/wiki/Merlin_(rocket_engine)#Merlin_1C_Engine_specifications

4.)RD-0242-HC.

http://www.astronautix.com/engines/rd0242hc.htm

5.)LR-87.

http://en.wikipedia.org/wiki/LR-87

6.)Pratt and Whitney Rocketdyne’s RS-18 Engine Tested With Liquid Methane.

by Staff Writers

Canoga Park CA (SPX) Sep 03, 2008

http://www.space-travel.com/reports/Pratt_and_Whitney_Rocketdyne_RS_18_Engine_Tested_With_Liquid_Methane_999.html

7.)RD-0124.

http://www.astronautix.com/engines/rd0124.htm

8.)Merlin (rocket engine).

2.5 Merlin Vacuum

http://en.wikipedia.org/wiki/Merlin_(rocket_engine)#Merlin_Vacuum

9.)Propep

http://www.spl.ch/software/index.html

10.)Newsgroups: sci.space.policy

From: Mitchell Burnside Clapp <cla…@plk.af.mil>

Date: 1995/07/19

Subject: Propellant desity, scale, and lightweight structure.

http://groups.google.com/group/sci.space.policy/browse_frm/thread/3d981607d59684dc/945baea33c95a22?hl=en

11.)Alternate Propellants for SSTO Launchers Dr. Bruce Dunn Adapted from a Presentation at:

Space Access 96

Phoenix Arizona

April 25 – 27, 1996

http://www.dunnspace.com/alternate_ssto_propellants.htm

12.)A Comparative Analysis of Single-Stage-To-Orbit Rocket and Air-Breathing Vehicles.

p. 5, 52, and 67.

http://govwin.com/knowledge/comparative-analysis-singlestagetoorbit-rocket-and/15354

13.)Reusable Launch System.

http://en.wikipedia.org/wiki/Reusable_launch_system#Horizontal_landing

14.)Landing gear weight (Gary Hudson; George Herbert; Henry Spencer).

http://yarchive.net/space/launchers/landing_gear_weight.html

15.)Mercury Capsule.

http://www.astronautix.com/craft/merpsule.htm

16.)Wired 9.12: From Russia, With 1 Million Pounds of Thrust.

http://www.wired.com/wired/archive/9.12/rd-180.html

17.)A Study of Air Launch Methods for RLVs.

Marti Sarigul-Klijn, Ph.D. and Nesrin Sarigul-Klijn, Ph.D.

AIAA 2001-4619

p.13

http://mae.ucdavis.edu/faculty/sarigul/aiaa2001-4619.pdf

The rocket equation states that about 90% of the Gross Liftoff Weight (GLOW) of anything going to orbit must be reaction mass that will be lost on the way up. (For a discourse on the rocket equation and its implications, see my SSX Concept essay.) Clearly the lighter you can make the structure of the craft, the better, so long as it’s strong enough; there have been many startling advances in material science in the last few years, and extremely strong spacecraft can be made from very light weight materials. This makes reusable spacecraft much more likely.

I haven’t followed the latest advances in structural materials as closely as I used to, but there have been some very favorable advances.

The DCX demonstrated that we can control rocket craft at low altitudes and speeds, and land them on a tail of fire. With the new structural material it ought to be possible to build a 600,000 GLOW reusable rocket that can either make orbit or scare it to death. This would be a highly desirable X Project, but so far nothing like it has been funded.