User talk:Wolfkeeper/Archive 3

Archive 1

Archive 2

Archive 3

Archive 4

Archive 5

Archive 6

Chiara Daraio research page (Acoustic metamaterials)

Here are the links for the West Coast college that I told you about:

Here is an overview of the research.

Here are the refereed journal articles.

I guess this is a page showing the people involved in the research.

- Wolfkeeper 05:04, 6 November 2009 (UTC)

Copasetic

I noticed you recently put a dictionary tag on Copasectic. I just ran into the article and loved it - it goes well beyond what a dictionary would do. How about the following? Do they fit in with Wikipedia's notability requirements? Lipstick on a pig and Fuhgeddaboudit? What's the official dividing line? Even if this is on the wrong side of the line, WP:IAR says keep it! Would you consider removing the tag? All the best, Smallbones (talk) 16:33, 9 October 2009 (UTC)

So your arguments are WP:ILIKEIT and WP:OTHERSTUFF?- (User) Wolfkeeper (Talk) 17:28, 9 October 2009 (UTC)

Note that encyclopedia articles do not 'go beyond' a dictionary article; they are simply different things, one is about a word, the other is about a thing- that is not simply a word.- (User) Wolfkeeper (Talk) 17:30, 9 October 2009 (UTC)

It's not just over the line, it's exactly antipodal from where it should be. I've never seen a clearer example of an article that deserves to die on dicdef grounds.

Wikipedia articles are about the subject,not about the word. There does not seem to be a single whole sentence that is not simply about the word.- (User) Wolfkeeper (Talk) 17:28, 9 October 2009 (UTC)

The official dividing line is WP:Wikipedia is not a dictionary.- (User) Wolfkeeper (Talk) 17:28, 9 October 2009 (UTC)

Encyclopedias are about bringing synonymous definitions and highly related things together and talking about them in one article because it provides for a place to compare and contrast and inter-relate. The other thing about encyclopedias is that they don't cover adjectives, longest, highest, tallest etc.; and copacetic is an adjective.- (User) Wolfkeeper (Talk) 17:28, 9 October 2009 (UTC)

Basically, every single thing it can fail on, it fails on.- (User) Wolfkeeper (Talk) 17:28, 9 October 2009 (UTC)

O.K., but could you tell me what you really think? :) Don't worry, everything's copasetic. Smallbones (talk) 19:25, 9 October 2009 (UTC)

I would like to stomp out dictionary articles in Wikipedia, but shy away from irritating people by the suggestion. If there is vote stacking effort for AfD, I am up for it, but Wolfkeeper seems to have taken all the good arguments already. I would try to find something significant to say, but if the good guys loose on this, I would not die of grief.--Fartherred (talk) 16:36, 19 October 2009 (UTC)

I don't agree with vote stacking. I don't do stuff like that, and I don't want others to either; I usually find that people that do stuff like that get blocked sooner or later.- (User) Wolfkeeper (Talk) 16:44, 19 October 2009 (UTC)

FWIW some dicdef articles like fuck will be very hard to get rid of (or turn into encyclopedia articles); I think it's better just to minimise the number of articles that are dictionary definitions, and make sure that the differences between encyclopedia articles and dictionary articles are explained very well to new (and old) users. If we can get the users to generally vote the right way for the wikipedia's purposes, then you don't need to do anything underhand anyway.- (User) Wolfkeeper (Talk) 16:44, 19 October 2009 (UTC)

Good man Wolfkeeper, we shouldn't resort to vote stacking, especially since it is directly against policy, it is ineffective in that votes are not the essential thing in consensus building and planning it here would be open to those with the opposing view. Now, I am not opposed to those who want to keep words knowing that some people are interested in getting rid of word articles, but spreading the word openly is not really vote stacking, is it? So how are those who participate in AfD informed of the process? I found out for myself that Wikipedia:WikiProject Deletion sorting/Language could be put in my watch list. If you run across people who would have some interest in this, you might mention it, especially if they are newbies like me.--Fartherred (talk) 05:42, 20 October 2009 (UTC)

Solar power

Hi, I noticed your edit to Space based solar power today by Zulu time, yesterday by Central Daylight. Is it common knowledge that thin film silicon solar panels are highly insensitive to ionizing radiation? This is outside of my field of knowledge. I am not even a well informed layman. I would like a reference to specific information on this point. Where should I look? Of course if you direct me to a good source, I will put it into the article as a reference. So help me beat you to it, please. (laughter aside) --Fartherred (talk) 16:33, 19 October 2009 (UTC)

Don't know. I know that SMART-1 for example went through the Van Allen belts successfully apparently without major degradation; I haven't managed to find out what sort of solar panels they use, but I suspect that is what they did. Apparently the ionising radiation tends to go straight through thin films causing little damage, whereas with thick films it tends to stop and presumably generates a shower of secondaries which cause damage. I haven't found a good refernece for it at the moment though; I heard about it on a recent program on the The Space Show, but I dimly recall hearing rumblings about it before.- (User) Wolfkeeper (Talk) 22:17, 22 October 2009 (UTC)

Thanks.--Fartherred (talk) 18:31, 24 October 2009 (UTC)

Need your opinion on some photographs

Hi. Can you provide you opinion on this matter? Thanks. Nightscream (talk) 02:00, 21 October 2009 (UTC)

Jet engine compressors

Hi, could you link this article in to deorphane it ? Jet engine compressors thanks Mion (talk) 15:18, 24 October 2009 (UTC)

edit conflict

Please pay closer attention to edit conflicts. Powers ^T 18:25, 1 November 2009 (UTC)

Sorry, I must have missed the warning at the top. It happens sometimes particularly with long articles, because I scroll down and don't notice it.- (User) Wolfkeeper (Talk) 18:57, 1 November 2009 (UTC)

Looks like you had a fan

[1] :-) --NeilN ^{talk ♦ contribs} 20:13, 4 November 2009 (UTC)

Yay!- (User) Wolfkeeper (Talk) 20:17, 4 November 2009 (UTC)

Your edits to N-body problem

You made a number of edits without edit summaries. It would be helpful if you'd indicate on the talk page the reasons for your removal of subject-matter. With good wishes, Terry0051 (talk) 08:39, 5 November 2009 (UTC)

Figures of speech

This is bullshit as well. Same problem as pissing contest. -- Scjessey (talk) 19:22, 6 November 2009 (UTC)

Well... tell me is the phrase 'Black hole' a figure of speech? It turns out that they're not black and they're not holes. Battle of egos, it's not a battle and the egos aren't doing the fighting. Does that mean that black hole shouldn't be used either?- Wolfkeeper 19:43, 6 November 2009 (UTC)

We need rules that can be used to cut through the clutter of these kinds of questions.- Wolfkeeper 19:43, 6 November 2009 (UTC)

In any case RELAX!!! There's always going to be articles that break a few rules in the wikipedia; the article fuck certainly does (and don't even try to delete that!!! 8-). Don't worry, it's not that important if a hundred or so articles out of three million+ are somewhat messed up. Sure, it's a good idea to reduce the number, but also it's more important to make the rules as easy and clear as possible.- Wolfkeeper 19:43, 6 November 2009 (UTC)

Discussion

Hi Wolf. It's probably going to be fixed by the time I post this, but your last post to the deletion discussion seemed to accidentally remove part of the content. Also, I've solicited input on the WP:content noticeboard regarding the lexicography and cultural content issues we've been discussing. I didn't want to revert your changes to articles I used as examples at the AfD, so I thought I'd see what other editors think about the issue. It's not an admin noticeboard or anything like that, so I hope you don't feel that it's meant to be confrontational. If my request is poorly phrased or misrepresents your view, please let me know and I will revise. Take care. Have a good weekend. ChildofMidnight (talk) 01:08, 7 November 2009 (UTC)

dicdef

I have reverted your edit to Pissing contest which inserted the {{dicdef}} template. This template includes the following:

Unless it can be turned into a full encyclopedia article in the near future,
Wiktionary Assessment Steps:

1. Check that this article meets Wiktionary's criteria for inclusion.
2. Check that Wiktionary does not have an article on this word or phrase, as verified using the search page.

If Wiktionary has a definition already: Change this flag to {{TWCleanup2}} or else consider a soft direct to Wiktionary by changing the text on this page to {{Wi}}. If Wiktionary doesn't have the definition yet: consider moving the whole article to Wiktionary by replacing this flag with the template {{Copy to Wiktionary}}.

I have removed it because

1) It does not, in its present state, come anywhere even close to satisfying Wiktionary's inclusion guidelines;

Irrelevant. The principle is that wikipedia is not a dictionary, not that it is not wiktionary.

2) There is already an article pissing contest at Wiktionary; and

Irrelevant also, see above.- Wolfkeeper 20:57, 8 November 2009 (UTC)

3) Because the AfD supersedes the need for any templates on the article anyway. Please relax. Things will be sorted out within a few days.

No, no it doesn't. There may be people that are reading the category that may have an opinion one way or another. Editing does not stop when an AFD is underway, and nor does the ridiculous mess that this article is. If the AFD fails, then the article will still need to be tagged anyway.- Wolfkeeper 20:57, 8 November 2009 (UTC)

-- Soap ^Talk/_{Contributions} 19:27, 8 November 2009 (UTC)

Uh, actually, Wolfkeeper, that template does seem to be intended for comparisons with Wiktionary. As it says, it should not be used if Wiktionary already has an article on that subject. {{TWCleanup2}} may be a better choice. Powers ^T 20:32, 9 November 2009 (UTC)

You can use either really, probably TWCleanup2 is better. The bot will do the process and put that on it anyway. Just putting dicdef on it is more user friendly though.- Wolfkeeper 20:40, 9 November 2009 (UTC)

Copying within Wikipedia

It appears that you recently copied or moved text from various articles on Wikipedia and Wiktionary to Credulity. While you are welcome to re-use Wikipedia's content, here or elsewhere, Wikipedia's licensing does require that you provide attribution to the original contributor(s). When copying within Wikipedia, this is supplied at minimum in edit summary at the page into which you've copied content. It is good practice, especially if copying is extensive, to make a note in an edit summary at the source page as well. The attribution has been provided for this situation, but if you have copied material between pages before, even if it was a long time ago, please provide attribution for that duplication. You can read more about the procedure and the reasons at Wikipedia:Copying within Wikipedia. Thank you. --Moonriddengirl ^(talk) 00:40, 12 November 2009 (UTC)

OK thanks.- Wolfkeeper 00:53, 12 November 2009 (UTC)

To be honest given the way I used the text, I'm not totally convinced that this is really necessary; it's pretty obvious that this article is subarticling those, and the history automagically makes it very clear who wrote what; if I hadn't linked them, then you would have a point, but there's a de facto implication here.- Wolfkeeper 01:17, 12 November 2009 (UTC)

f —Preceding unsigned comment added by 83.12.233.134 (talk) 10:38, 12 November 2009 (UTC)

The history does not make it at all obvious that this was built from other articles. –xeno^talk 13:48, 12 November 2009 (UTC)

I'm afraid that there aren't "de facto" implications when it comes to copyright. You must provide specific attribution. And even if that were acceptable, you didn't link to or mention Wiktionary:credulity, which also requires attribution. --Moonriddengirl ^(talk) 14:10, 12 November 2009 (UTC)

Please leave notice

Hi there; could you please leave a notice at Phil Spectre's talk such that he knows to defend himself at the sockpuppetry investigation that you initiated? Thanks, Awickert (talk) 03:48, 17 November 2009 (UTC)

steam rocket

You're the main contributor to this page (almost!). Have you seen this edit? -- EdJogg (talk) 13:51, 18 November 2009 (UTC)

Re: Kia kaha

Dear Wolfkeeper -why do you repeatedly mark Kia kaha as a dictionary entry only? I do not doubt that a separate item on Kia kaha in Wiktionary would be useful, but what is currently at Kia kaha should not be directly copied as it is encyclopedic, and considerably beyond a dictionary entry, and can be expanded still further. Grutness...wha? 22:45, 26 November 2009 (UTC)

Encyclopedia articles don't go beyond dictionary entries, they are different in kind. Dictionary articles are characterised by defining a term, the usage of the term, and the etymology of the term. Encyclopedia articles are on a topic, that is not a term.- Wolfkeeper 22:54, 26 November 2009 (UTC)

By the way, it's extremely inappropriate to remove a tag that simply copies the article to Wiktionary. The only reason I can think of for not doing that would be if you think this is not a valid term at all.- Wolfkeeper 23:16, 26 November 2009 (UTC)

You've answered your own question. "Encyclopedia articles don't go beyond dictionary entries, they are different in kind". This is an encyclopedia entry, not a dictionary entry - i.e., it is inappropriate for this to be directly copied as a dictionary entry. I have no objection to a separate, different, entry on Wiktionary about Kia kaha. However, the current article is not and cannot be considered a Wiktionary entry and as such it should not be copied into Wiktionary, as it would be inappropriate there in this form. It should have a separate article written there, using some of the information from the Wikipedia article. That is not a copy, it is a rewrite. There is also often the implication in using {{copy to Wiktionary}} that once an article has been copied it may be removed from Wikipedia. I wish to avoid seeing that happen. Grutness...wha? 00:45, 27 November 2009 (UTC)

Sigh.

The copy tag simply kicks a bot, which run occasionally, but copies the article into the transwiki section of the Wiktionary. A human editor in Wiktionary land tjem takes this article and manually formats it appropriately for Wiktionary. This method is used because it maintains the history of the copying for GFDL purposes.

The bot does not trigger a delete; whether the article is deleted or not is to do with the AFD process in the Wikipedia.- Wolfkeeper 00:57, 27 November 2009 (UTC)

I stand corrected, though I am sure the implication has been used as justification for listing articles for deletion in the past. Grutness...wha? 00:29, 28 November 2009 (UTC)

Re: Power to weight ratio

Adding in some entries in this table is OK, but this is not really intended to be a complete list of all the cars ever, it's just some to give an idea. The wikipedia isn't a list of indiscriminate information about cars. I think the list is already too long now.- Wolfkeeper 04:24, 1 December 2009 (UTC)

Point taken, and I'll refrain from adding any more. However the models chosen are to show where different iconic vehicles reveal themselves in terms of the power-to-weight ratio metric specifically. This can inform green debate (Gasoline vs. Electric vs. Hybrid Gas/Elec vs. Turbodiesel vs. Hybrid Turbodiesel/Elec vs. Steam), east-west energy debate (autorickshaw, Tata Nano, Bajaj motorbikes vs. hummer, GMC Pontiac/CR8 vs. Prius Smart Fortwo), mass transit (Chunnel TGV vs. personal mobility, technology improvement (Benz, Model T vs. Prius, turbocharging), body shape (Ford Focus ECOnetic vs. Ford Fiesta ECOnetic), market and performance point choices inc. by NATO/USMC, and performance records (eg. thrust supersonic car, thunderbolt).

Perhaps a rationalisation review is worthwhile?

An alternative would be to create these implicit comparisons explicit. This could be more useful to the reader, and cast this page from a "data sheet" format to connect with such wikipedia entries. The value and non-value of the metric would then be revealed to the reader.

Your opinions would be welcome.

—Preceding unsigned comment added by 124.170.228.102 (talk) 05:20, 1 December 2009 (UTC)

Dunno, just have a range. The other thing is that 'vehicle' doesn't only include cars. It might be worth having a separate table for cars though.- Wolfkeeper 13:07, 1 December 2009 (UTC)

Patent

Hi, good catch on my mistake. I read on several sites that patents regulate commercial use only, which sounded like common sense to me and ethical. Apparently, there are many others that believe this to be true, since other website say the same thing. After your edit, I read the actual US patent law and was shocked that a patent is considered infringed upon simply for making the patented item! So if someone patents a way to make or grow food, I cannot make or grow that food on my own property for myself or my children to eat without having permission of the patent holder. This seems unethical to me, but that is the law the US government chose to adopt. Vanadyl (talk) 21:01, 2 December 2009 (UTC)

It's actually slightly worse than that; you could already be doing something, and somebody gets a patent on what you're already are doing, and then you have to stop. Only if you can show that you were doing it before the patent was issued, can you carry on; but even then you can't make obvious changes to what you're doing that would infringe the patent.- Wolfkeeper 21:10, 2 December 2009 (UTC)

Yikes, that is a scary thought. If you have no intention of patenting your idea, you could make a video and post it online, to document your "prior art". Vanadyl (talk) 05:27, 4 December 2009 (UTC)

Yes, if you publish it, that's prior art; and in the US you have up to a year to choose to patent it. However, in the UK, telling anyone about it means you can never get a patent on it.- Wolfkeeper 05:34, 4 December 2009 (UTC)

Don't revert removal of xkcd links

You need to give a reason for putting xkcd links in an article. Wikipedia isn't an xkcd fan-site. WeDon'tWantAny (talk) 07:34, 5 December 2009 (UTC)

The use of cartoons like this to illustrate difficult topics has a long history in physics. As it happens whether this should be included or not, this question came up before, and the decision was that we actually want to include the cartoon in the article if at all possible. The cartoon is after all, technically accurate and penned by a professional physicist.- Wolfkeeper 13:55, 5 December 2009 (UTC)

Please find the discussion for reference. Until then the link stays out of the article. I don't buy your reasoning (the comic explains nothing to the reader, and is simply an in-joke for people to feel pleased about getting). However, if you truly believe what you're saying, I'm sure you'll be happy to see the xkcd comic replaced with something I've scribbled on a piece of paper (it's a comic featuring stick-men explaining the principles of centrifugal forces). Being completely neutral about xkcd I'm sure you will be happy to see this included. WeDon'tWantAny (talk) 17:35, 5 December 2009 (UTC)

Feel free to scribble stuff and upload, and I'm sure we'll treat it according to its applicability to the article. In the meantime the XKCD cartoon is actually notable in this context.- Wolfkeeper 17:49, 5 December 2009 (UTC)

Ridiculous, you even say yourself that the comic will probably get removed because of tone in that original discussion. Why not run with that feeling instead of rabidly defending its inclusion because *you like it*? WeDon'tWantAny (talk) 22:32, 5 December 2009 (UTC)

The cartoon is on topic and entirely appropriate and to the point; indeed I want it in the article and this was agree by the other editors, and the only reason it isn't is because we haven't been able to negotiate a license. If you read the WP:EL guidelines, you'll find that makes it eligible for inclusion in the external links section; we are allowed to include references to things we are not able to include- that is correct linkage.- Wolfkeeper 22:40, 5 December 2009 (UTC)

I have copied this discussion to the talk page of the article. I suggest we continue it there. WeDon'tWantAny (talk) 22:46, 5 December 2009 (UTC)

At the moment there are license issues, I did send a request to the copyright owner to see if he would agree to relicense it; I never got a reply, but I may ask this again though; apparently he gets swamped with emails, so he may not have read it.- Wolfkeeper 13:55, 5 December 2009 (UTC)

Scramjet

Hi Wolfkeeper,

Saw your recent edit to scramjet and didn't want to revert without talking to you first. Actually your edit is not correct. Slowing the flow down through a shock system causes a loss of total pressure which is not recoverable. This is pressure drag, and is a problem for all transonic/supersonic bodies. If we know that the flow is slowed down to Mach 1, then the exact amount of pressure drag generated can be computed. This converts to an energy knowing the mass flux of air coming through the inflow.

Each fuel which burns in air at the stoichiometric ratio at a constant initial temperature releases a certain amount of energy per unit air, which depends only on the type of fuel. Giving some low starting temperature (say 300K), a value for the maximum releasable energy from a given mass of air for a given fuel can be computed. This number is smaller than the pressure drag energy loss for scramjets. Thus the point of scramjets is to reduce the pressure drag sufficiently that it will be recoverable by normal fuels.

The topic you approach has to do with precooling, and is of course an important topic for all high speed engines. as you know, there are a number of designs to precool the air for turbines or ramjets to extend them to around Mach 3-5. Although precoolers (or injecting cold fuel, or other cooling tricks in combination with flameholders or igniters) can improve the efficiency of scramjets, or other combusting engines, they do not solve the fundamental problem of the huge wave drag. Thus drag is actually the fundamental problem for scramjets.

Regards, AKAF (talk) 10:14, 8 December 2009 (UTC)

You're (partially) right, there is a reduction in pressure- the temperature goes up, and the pressure goes down, which if you think about it is an increase in entropy- it's irreversible; in principle you could just burn more fuel to make up for it if that was the only problem.

However, at about Mach 5.5 the temperature gets so high after transiting through the normal shock that the air actually chemically reacts (the definition of hypersonic), you get N2 + O2 reactions, which absorb energy and can't be easily reversed either. So you've lost O2 to burn as well. Then the combustion process doesn't give you much increase in temperature of the air; so the nozzle gives far less thrust, and it's difficult to get any net thrust at all.- Wolfkeeper 18:16, 8 December 2009 (UTC)

The precooling schemes don't help with this, because the air has already reacted before entering the precooler.- Wolfkeeper 18:16, 8 December 2009 (UTC)

Scramjets avoid this issue by not having a normal shockwave, they don't slow the air to subsonic speeds. That's why they're theoretically good for Mach ~17. But rockets are very efficient above Mach 10 or so anyway.- Wolfkeeper 18:31, 8 December 2009 (UTC)

Wave drag is something a bit different; that's the energy lost in shockwaves that radiate out away from the vehicle. It's a big nuisance certainly, and probably would be worse for scramjets due to the high speed.- Wolfkeeper 18:31, 8 December 2009 (UTC)

I miswrote pressure drag as wave drag that last time, and I assume that you mean a reduction in total pressure in the first sentence? Actually pressure drag can be tracked back to the loss of total pressure across a shock, see Normal_shock_tables. The energy recoverable in a nozzle is a direct function of the total pressure. So at Mach 5 you're only recovering 6% of the drag from the inlet in the nozzle, for a simple flow-through design with a normal shock. (One can consider the recompression part of a transonic airfoil as a one-sided nozzle in this case, and the problem with pressure drag is that the recoverable energy is decreased by the shock.) The pressure drag is a direct function of the Mach number, and once the recoverable energy falls below that generatable by stoichiometric combustion then the scramjet can't work. For an air-breathing engine, the stoichiometric ratio puts a hard limit on the energy which you can get out of the fuel, which is why most precoolers in aircraft currently flying work by spraying liquid oxygen into the flow in front of the first compressor stage. I know SABRE doesn't work like that, but it's not exactly a standard precooler. I'm not implying that what you're saying is wrong, just that it misses the point. Even if you could magically solve the fuel temperature problem, the drag would still not be less than the thrust.

My point is that your rewrite puts undue weight on the reaction problem due to increased temperature, when, even if it were solved, the total pressure loss over the shock would kill you anyway. AKAF (talk) 09:08, 9 December 2009 (UTC)

Incidentally, the nitrogen-oxygen reactions are a small energy problem, dissociation is not a serious problem below Mach 8, and it is rather difficult to tell what effect these reactions have on a constant-temperature flow because all of the NOx variants are part of the hydrocarbon reaction chain, and small amounts will be beneficial to the reaction rate and flame stabilisation. AKAF (talk) 09:08, 9 December 2009 (UTC)

Well, in a sense it doesn't matter, we need good referenced material; in the wikipedia that's the final reality. At the moment it's not referenced.- Wolfkeeper 21:49, 9 December 2009 (UTC)

Specific Impulse

You just revoked my modifications to this article... Let me explain myself. Also, excuse weird semantic because I'm not a native English speaker, but this does not implies I'm not qualified to argue on this topic.

When you speak about the definition of propellant, I cannot agree with you. The wikipedia page states : «A propellant is a material that is used to move ("propel") an object.» which does not imply that the propellant must be on the craft.

The propellant article was horrible- I've rewritten it a bit; it did actually say that already in the 'trivia' section; it's a lot easier to read now.- Wolfkeeper 06:30, 20 December 2009 (UTC)

Oh well, good to see this was improved.

Whatsoever, my objections, are not on the base of the definition of propellant...

«Note that an air-breathing engine is thus much more propellant efficient; this is because the actual exhaust speed is much lower, because air provides oxidiser, and because air is used as reaction mass.»

I understand what this sentence means, but it is rather misleading. In this part of the article, it is stated that the propellant efficiency is higher partly because the exhaust speed is lower which is completely not true. In fact, a lower exhaust speed means a lower Isp, and I am not confusing effective and real exhaust speed here.

I'm sorry, but yes you are. The energy for duct engines comes from the propellant (i.e. fuel). When the air leaves the engine more slowly but the airflow is scaled so that you get the same thrust then you need less fuel flow; and Isp has gone up. You'll see why when you read down a bit.- Wolfkeeper 06:34, 20 December 2009 (UTC)

No I'm not. You think I'm confusing them because of the direct assumption that a lower effective exhaust speed means a lower Isp which I'm not doing. What I wanted to show is that in a normal self-containing reaction drive the lower the real exhaust speed, the lower the Isp, but in the case of air-breathing engine, the reaction drive is NOT self-contained, and this relation does not hold. But, it is not BECAUSE the actual exhaust speed is lower that the Isp is higher... In the counter-argument you gave me, you said that the airflow is scaled, because the flow is slower, but all of this is dependent ont the fact that these engines use mostly external reaction mass, and this is the big difference, not the exhaust speed.

The fact is that the efficiency of an air-breathing engine is lowered by its lower real exhaust speed but so much more boosted by the fact that most of the propellant (or reaction mass, if you don't agree on definition...) and the oxidizer is not carried along, while the Isp calculations consider only the fuel on-board as the only reaction mass.

It's actually more complex than that. The ideal efficiency is when the exhaust speed and the airspeed are the same (although they can never be exactly the same with airbreathing vehicles otherwise, simplifying very slightly, you get no thrust). (See propulsive efficiency). With turbojets the exhaust speed is (for complicated reasons) for subsonic flight, too high. Adding the bypass ducts lowers the effective exhaust speed closer to the airspeed and efficiency goes way up. On the other hand Concorde did very well with turbojets, but it was flying much faster.- Wolfkeeper 06:30, 20 December 2009 (UTC)

The reasons behind the efficiency boost you speak about comes from the corrections of inefficiencies inherent to evolving in a fluid medium, but it is not relevant to the Isp. It is sure that since planes use their propellant as an energy source, then reducing whatever drag (or the like), will enhance the energy efficiency and thus the fuel efficiency, but the Isp is a general concept concerning mainly quantity of movement, speed of exhaust, and mass flow of the exhaust. Somehow, taking it like it is in the article is twisted in my opinion and not relevant to a page on Isp, because introducing practical concerns not related to the conservation of momentum law, from which the concept of Isp is coming, is making the text heavier to read, unless the above discussion is mentionned. But again, this would be out of topic.

I would like to explain myself a bit more: To enhance performance of a reaction drive, you can increase it's Isp OR correct inefficiencies. Somehow, it works out that in the case of airplane, you can enhance turbulence or drag characterisitic (I don't really know but that's not relevant) which will enhance energy efficiency, and thus fuel efficiency or propellant efficiency in the case of planes, but you're not enhancing propellent efficiency from the point of view of Isp, rather from the engine overall efficiency point of view. I know that Isp IS propellant efficiency, but in the case of air-breathing engine, the notion of Isp becomes all non-sense because the fluid medium in which it is evolving and which is part of the reaction mass links everything up. Overall, it is off topic, and thus kond of false... —Preceding unsigned comment added by 65.92.160.15 (talk) 07:47, 20 December 2009 (UTC)

Moreover, the conservation of energy and the laws of movements are distorted in the following statement:

«Since the actual, physical exhaust velocity is lower, for at least subsonic speeds the kinetic energy the exhaust carries away is lower and thus the jet engine uses far less energy to generate thrust.»

Firstly, not considering the inefficiencies of a particular system, the energy used to generate a given amount of thrust is stable since we're working with reaction drive: For a given delta p there is an average impulse required to be apply, but since it's a reaction drive, this average impulse implies an equal delta p in the opposite direction. A reaction drive accelerates mass to produce the required average impulse, and the energy required to get a given quantity of mass to a given speed is constant.

And yes, an air-breathing engine is a reaction drive, not just rockets. Planes take-in air, add kinetic energy to it by heating it and then passing it through a nozzle, and then eject it to gain some more speed or quantity of movement (p).

Also, the kinetic energy carried by the exhaust is not lower, it is stable for a given thrust, because if the velocity of the exhaust is lower, the mass of it is higher (the flow is higher). —Preceding unsigned comment added by 65.92.160.15 (talk) 06:02, 20 December 2009 (UTC)

No, that's not correct and it's wrong because energy is a square law on speed, but momentum is a linear law. It's easiest to see from the ground reference frame; the engine gulps in some stationary air, and then gives it backwards speed to give thrust. If your engine rams in twice as much air per second and then throws it backwards at half the speed, you need only half the amount of energy, but you get the same thrust. That's why turbofans are more efficient the better their bypass ratio is.- Wolfkeeper 06:30, 20 December 2009 (UTC)

Yeah, I misread that sentence, you're right about the KINETIC energy, but not just energy, as mass is still energy. But I still find the above sentence confusing because, and that's what made me react, it seems to imply that air-breathing engines are more efficient BECAUSE the real exhaust velocity is higher, while it's more because mass is more used then speed to change p than in other types of reaction engines(I recognized this last sentence is really weird of semantic, hope you understand).

Skylon reorganisation

I recently reorganised the Reaction Engines Skylon article, fancy taking a look at the new layout? Anxietycello (talk) 23:07, 23 December 2009 (UTC)

Looks very good.- Wolfkeeper 00:19, 24 December 2009 (UTC)

Merry Xmas

File:Christmas Barnstar (aviation).jpg

Merry Christmas and Happy New Year from Bzuk (talk) 20:39, 24 December 2009 (UTC).

Thanks! And the same to you, and may you have a happy new year!- Wolfkeeper 22:58, 24 December 2009 (UTC)