Talk:Atmospheric entry/Archive 1

Archive 1

Archive 2

Please do not litter the article with "citations needed" comments

Much of the work related to atmospheric reentry is either classified or ITAR restricted or the original sources have died/retired. There is a whole body of information about Atmospheric Entry (some of the most interesting aspects) that is purely anecdotal where there is no written reference (this Wikipedia article would become the written reference). This is not like an article about the Bible or Thucydides where every phrase could be referenced to three or four different textual sources. If you see something where you know what the reference is then PLEASE provide the reference. However please don't degrade the article by tagging every other sentence with "citations needed". Egg plant (talk) 20:56, 16 February 2009 (UTC)

There is no getting around it, though... this is not a well written article. It needs better research and many, many more citations. Also, as a government crony myself, I do not for a nanosecond believe that stuff about not being able to cite something because it is "classified" or "ITAR restricted." Obviously the information is not restricted. Ridiculous. Gingermint (talk) 03:58, 26 January 2011 (UTC)

Please do not edit this article if you know nothing about atmospheric reentry

I just cleaned off a bunch of edits made by someone who was clueless. Please do not edit this article if you know little or nothing about atmospheric reentry. Egg plant 05:02, 2 November 2007 (UTC)

Actually, anyone can edit is a core policy, so just make sure you have a reliable source for your information. It's only rocket science, for crying out loud. User:Pedant (talk) 04:18, 29 March 2008 (UTC)

Yes, exactly. Under our behavioural guidelines, I'm afraid Egg Plant is way out of line here. The correct procedure is to correct the errors but to avoid personal attacks, avoid biting anyone (particularly the newbies but not only them), and to post an encouraging explanation on the talk page of the contributor if at all possible. Andrewa (talk) 15:30, 5 February 2009 (UTC)

Yes, anyone can edit and anyone else can delete. That's the great strength/weakness of Wikipedia. When it concerns the article about Bugs Bunny then it doesn't really matter who makes the edit (we are all experts about Bugs Bunny). However Atmospheric Reentry is one of the toughest technical topics out there and very few people have expertise in it. If you have a clue about aerospace engineering then PLEASE contribute to this article. Egg plant (talk) 20:37, 16 February 2009 (UTC)

Quite simply, if all assertions in the article are supported by verifiable citations, we'll be a long way toward an article that has no issues with Wikipedia policy that "anyone may edit." That and, for more controversial edits, there is always the opportunity to bring it to the Talk page for discussion and an attempt to build consensus, or at least all get on the same page with respect to the way in which a good encyclopedia is built. Cheers. N2e (talk) 02:04, 17 November 2010 (UTC)

Sphere/Cone vs Blunt Body

One comment I'd like to make... the current (2006-01-16) article seems to conflate sphere-cone and blunt body type reentry vehicle shapes, which isn't entirely accurate based on the common usage. There are really three variations here... sphere-cone, with the sphere having a large radius compared to the base radius (0.5 or greater ratio); blunt body, with a smaller nose radius than that, and with a large body angle (45 deg or greater); and conical, with a smaller nose radius than that (typically 0.1 or less), and a small body angle (typically around 20 degrees). The defining examples would be say a Discovery film return capsule for Sphere-Cone, oh... Viking, say for Blunt Body, and any modern ICBM RV for Conical.

The article has improved tons over the last couple of months, and that's much appreciated, but the more we can do the better 8-)

Now back to Acusil-I, writing some 6 DOF entry code, and International Space Station visiting vehicles specs. Groan. Georgewilliamherbert 07:30, 16 January 2006 (UTC)

You're point about blunt bodies is well made. I need to make it clear that there are two classes of entry vehicles, i.e. military RVs and space exploration entry vehicles. The concept of a blunt body for a military RV was abandoned with the Mark-2 RV. Carbon phenolic nose tips made high ballistic coefficient RVs practical. The faster transit time through the atmosphere made RVs more difficult targets for ABMs.

Egg plant 17:46, 17 January 2006 (UTC)

I'm not sure that all earth atmospheric re-entrys heat up to 7800 K. The space shuttle can only take 2300 F on the most heat resistant parts. There has got to be an equation here with the surface area, weight, and speed . cc

Hi. For your information, you can sign comments by typing four ~ characters in a row without any spaces.

The great innovation behind blunt reentry vehicles in the 1950s was that by making it blunt, the shockwave and peak heat are pushed back away from the skin of the vehicle. Since they aren't in direct contact, the actual heating of the vehicle is lessened. Most of the heat energy stays in the shocked gas that just moves around the vehicle, so the heat is mostly just dissipated into the atmosphere. If it wasn't, the vehicles would all melt as they were coming back in. Georgewilliamherbert 03:00, 29 January 2006 (UTC)

Thanks 24.137.78.34 16:15, 29 January 2006 (UTC)

George, I reworded your above explanation and included it in the section about blunt body theory. Egg plant 17:13, 16 February 2006 (UTC)

RVs in current times

~~MV~~

The RVs of today's nuclear weapons (Minutemen, SLBMS) seem to use ablative TPS. Were the heat sink types abandoned as well as the blunt body shape with the early RVs? It could be pointed out in contrasting military Rvs to non-military space vehicles.

Yes, the heat sinks were abandoned. In terms of energy absorbed or redirected per unit mass of thermal protection system, the ablative options are superior to any of the alternatives. Reusable lightweight TPS is heavier than ablatives, and heat sinks are considerably heavier. Ablatives also can deal with higher heat fluxes. The older blunt body RVs slowed down a lot during their reentry; modern ones stay hypersonic down to ground level, to improve accuracy and make interception harder, and going mach (many) at sea level is incredibly high heat flux. Georgewilliamherbert 19:03, 4 February 2006 (UTC)

I've never worked on military RVs and don't have access to classified information. However reports concerning the Mk-6 and Titan-II have been declassified. From those reports it is possible to reconstruct the trajectory of the Mk-6 to the altitude of its fuze setting. The speed of the Mk-6 at that altitude was 560 m/sec or Mach = 1.7 .

There is a movie floating around the web showing RVs from a Peacekeeper missile coming into Kwajalein. The RVs were white hot but looked like they were going low supersonic. I don't have a clue how they would fuze the nuclear warheads in an RV. The fuze would have to be very reliable but not spoofed by the significant G forces experienced by the RV or by buffetting and over pressure from an ABM near miss. A radar altimeter based fuze would not work if the RV's shocklayer was ionized. I see the technological limitations of the fuze forcing the RV to be low supersonic when it reached its target altitude.

Egg plant 00:51, 12 February 2006 (UTC)

~~MV~~

If I have understood your explanation correctly, heatsinks and radiative cooling could not be even low supersonic and slowed down greatly during re-entry.The ablation type is the only TPS that can protect the bomb can effectively and keep the speed supersonic or over Mach 1.2,making it superior in accuracy to heatsinks or other form of TPS, therefore its use in modern RVs such as Minutemen and Tridents.

Did I get that right?

RV shapes and Ablative materials

~~MV~~

I think the comment mentioned about RV's shapes nowadays is well made. The current RVs as the ones present in the minutemen and trident missiles are conical in shape, not quite a sphere-cone. Could I make a change in this mention and probably an specification that current military RVs are ablative types?

The article also seems to hint that ablative materials are not metals, but instead based on carbon materials. Is there a reason why the ablative materials of modern RVs (as minutemen and trident missiles) are not metals? Or is the weight of the metals the only reson why they are not used as ablative materials?

to be a good ablative material, it needs to burn or ablate...metals do not behave this way...they just heat up.Anlace 06:09, 7 February 2006 (UTC)

Modern RVs as used in the Minuteman and Trident missiles are sphere-cones with small nose radii. Carbon-phenolic or carbon-carbon is typically used for the nose tips because they get really hot (convective heat flux scales with the reciprocal of the square root of nose radius).

We take carbon for granted because it's so common (carbon is a major component of our bodies). However carbon is the most refractory substance in the universe. Carbon has a higher melting point than tungsten. Normally carbon never gets a chance to melt because it burns before it reaches its melting temperature which is also a good thing if carbon is being used as an ablator.

Egg plant 05:43, 10 February 2006 (UTC)

There's also been some work with low-regression stable refractory metal tips, some of which have some slight porosity and an ablative filler (or small holes drilled and an ablator inserted). The tip ablating slightly unevenly can otherwise cause slight flightpath changes. That seems to be an advance in reducing accuracy dispersion down into the 100m range. Georgewilliamherbert 06:01, 10 February 2006 (UTC)

Disambiguation and bypassing redirects

Hi there, Variable. It seems you and I disagree on whether the link to Reentrant dysrhythmia (which is a subtopic redirect page) should be bypassed by linking to Cardiac arrhythmia directly. While bypassing redirects is a general waste of time anyway (see Don't fix redirects that aren't broken, Can/should redirects be cleaned up?, and About fixing directs if you're not convinced), subtopic redirects should never be bypassed since they will eventually be fleshed out into real articles. There are several reasons for this, not the least of which is that it creates a great deal of work for us later: when the subtopic redirect is replaced with real content, every link that was bypassed to point to the main topic will have to be updated to point to the original subtopic page.

So I've replaced the bypassed link once again with a link to the subtopic redirect, i.e. Reentrant dysrhythmia. If after you've read the pages I referenced above, you still feel compelled to bypass the redirect, please discuss it before reverting my change. Thanks and best wishes, David Iberri (talk) 00:31, 16 February 2006 (UTC)

This is not necessarily saving us work later, given that Reentrant dysrhythmia is not an article on its own and may, or may not, ever become one, and that even if it does the redirect will likely be removed altogether as it will likely result in reentry becoming a disambiguation page. That is, either way it will have to be altered on this page once the article for Reentrant dysrhythmia is written, as atmospheric reentry is not by far the most common meaning of reentry (this, of course, is IMHO). Therefore, I thought (and think) it better to have the redirect here be directly to the target page in the case that its ever moved (ICD diagnoses might come under different names in future revisions, for example). In short, I don't disagree with the general principal that it's not important to fix redirects that aren't "broken", but in the case of disambiguation link to a subtopic it's a bit different because the creation of the article will change the dab link anyway. siafu 01:26, 16 February 2006 (UTC)

I know I'm biased, but I think that atmospheric reentry is by far the most common meaning of reentry... Georgewilliamherbert 04:31, 16 February 2006 (UTC)

Given that the vast majority of topics for which an encyclopedic article could be written generally do receive entries on Wikipedia, it's reasonable to assume Reentrant dysrhythmia will one day have its own article. It's therefore natural to treat a link to Reentrant dysrhythmia or any other subtopic redirect as a bona fide article. So if you feel that Reentry should be a disambig page, then it would be appropriate to turn it into one now, listing Atmospheric reentry and Reentrant dysrhythmia for starters. I would have done that originally except that I think atmospheric reentry is the more common meaning of the term reentry. Cheers, David Iberri (talk) 04:56, 16 February 2006 (UTC)

I've discussed this with George Herbert. Following his advice, I'm not going to take any further action concerning this disambiguation. Based on what George tells me, there is no attractive way to disambiguate in the Wikipedia format. Egg plant 16:39, 16 February 2006 (UTC)

Most topics that could be written generally have not received entries on wikipedia, and given the nature of the advance of human knowledge it is likely to stay that way. It is not useful to assume that an article will "one day" be written simply because it could; wikipedia is not being prepped to be used by readers "one day" off in the future-- it is being used now. It could be months, years, or eternity before Reentrant dysrhythmia is turned into an article (unless you know something I don't there), so all else being equal, the link should put the article its linking to directly and not through a redirect because (and it happens) articles do sometimes move around, leaving redirects behind. The original page you pointed to in this argument, however, says: Some editors are under the mistaken impression that fixing such links improves the capacity of the Wikipedia servers. But because editing a page is thousands of times more expensive for the servers than following a redirect, the opposite is actually true. Since not only was the change reverted, but we've gone ahead and posted multiple times here on the talk page, this is all essentially moot. siafu 19:36, 16 February 2006 (UTC)

Sphere-cone paragraph

~~MV~~

It is mentioned in this paragraph that the MK-2 Rv used a radiatively cooled TPS based upon a metallic heat shield, but the Mk-2 used the heat-sink concept. It seems that unlike the ablative or thermal soak TPS, the heat-sink does not work as a protector of heat to the aeorshell or the payload, it only conducts the heat away form the shell of the RV. Was the mention of a metallic heatshield referring to the heatsink or does the heatsink concept also have a heatshield besides the copper heatsink?

FYI, You can sign your comments by typing four ~ characters in a row with no spaces...

There was usually some internal insulation between the heatsink TPS and the main body of the entry vehicle; keeping that heat out of the main body of the vehicle was the point. There usually isn't any sort of external coating or heatshield; the heatsink (copper, beryllium copper) is usually exposed straight to the entry gasflow, and though you hope and design that the shock will carry most of the heat away and around, dissipating in the atmosphere, radiant heating and residual frictional and hot gas contact heating will directly heat up the heatsink material.

There's no effect such as the outgassing in ablative TPS systems, where the gas being sublimed out of the surface pushes the hot atmospheric shock heated gas back and away from the ablative surface.

There doesn't seem to be a happy medium where you mix the two approaches. Either your application optimizes all for one way of doing it, or all for another.

Georgewilliamherbert 08:47, 19 February 2006 (UTC)

Heatsink in modern times

Was the heatsink ever improved to be used in high-beta missiles or current space shuttles or did the weight make them impossible to use in such way? It seems like radiative cooling is still used in space technology, but all MIRVS seem to make use of ablative TPS nowadays. Why couldn't heatsinks be used im MIRVS?

Mario Lopez 22:16, 10 April 2006 (UTC)

Heatsinks were too heavy. Ablators are much more mass efficient. Every gram wasted on an inefficient thermal protection mass could have gone instead to payload mass.

Egg plant 06:59, 2 May 2006 (UTC)

History dispute?

The intro is now the "History" section, but I still think it has some problems. No one ever considered human spaceflight until the soviets decided they could have propaganda, well after ICBMs?

Sure, they considered it, just like people considered human flight well before the Wright brothers, they just didn't have a clue how to do it until the ICBM research.WolfKeeper 17:22, 7 May 2006 (UTC)

The history it lays out is pretty much contradictory to my understanding of the causes behind the space race, and it cites no sources, which means there's no way to verify the sequence of events it describes. I think it could stand to be trimmed and rewritten to focus on how people came to understand the problem itself, rather than colorful speculation about ending on dreary notes and a flawed description of the space race. Did von Braun consider reentry, for example? Night Gyr 08:23, 3 May 2006 (UTC)

The dispute tag has been misused. It is for use when:

• it contains a lot of unlikely information, without providing references.
• it contains information which is particularly difficult to verify.
• in, for example, a long list, some errors have been found, suggesting that the list as a whole may need further checking.
• it has been written (or edited) by a user who is known to write inaccurately on the topic.

(see: Wikipedia:Accuracy dispute). The facts are that reentry was made possible by Allen who was doing research on reentry for ballistic missile research. I've read the (now declassified) paper. The history section says this, and (IMO atleast shows little if any connection to your description above). Unless you can defend your description and show likelyhood of factual statements I have removed it.WolfKeeper 17:22, 7 May 2006 (UTC)

reentry made possible? what do you mean? isn't the first item that reentered (a v2 then) the thing that confirmed our option to reenter? or perhaps i miss the point.24.132.171.225 (talk) 01:42, 3 October 2009 (UTC)

Definitions list cleanup

I think the list of jargon needs pruning, too. Several of the entries can be combined, for example, outer mold line doesn't need a separate entry from aeroshell, I think, and we don't need to include Mach number here, it has its own article. Night Gyr 08:32, 3 May 2006 (UTC)

I just put the IMU and RCS definitions back in; those have links back to the main articles on those topics, and the descriptions here are appropriately short and contextual IMHO.

Outer mold line defines the outside shape of the aeroshell; we might be able to combine those two entries, as long as both terms are listed (both are used individually and unambiguously in different areas of reentry analysis). I think that a short defining note and link to the Mach number article are still important. Georgewilliamherbert 18:02, 3 May 2006 (UTC)

I would argue that most vehicles intended to reenter the Earth's atmosphere are ICBM RVs and not orbiting spacecraft. Therefore the original introduction was factually incorrect and has been corrected. I tweeked the image arrangement to make it more tidy. I'm tempted to add more content (describe the chemistry of shocklayer radiative heat flux) but unfortunately the article has gotten too long. Egg plant 18:05, 6 May 2006 (UTC)

A lot of the size is the list of definitions, that seems to take up half the article. I think it might help to rewrite it in prose to cut down on redundancy and then just bold each term. I'm going to put the orbit example back in, also mentioning ICBMs, because while ICBMs are the most common RVs out there, deorbiting craft are the most common actual events. Night Gyr 20:20, 6 May 2006 (UTC)

How about an intermediate compromise? I don't like the idea of doing it as prose, but we could do a traditional list (* chars) and trim most of the definitions to one (or at most two) lines... Georgewilliamherbert 20:27, 6 May 2006 (UTC)

I revised the introduction again. The article describes entry vehicle's entering the atmospheres of nonterrestrial planets from heliocentric orbit. Using the language "Earth orbit" is too restrictive. Also the United States and presumably the English, French, Chinese, Iranians, North Koreans and Russians are doing ICBM readiness tests on a regular basis (also the more advanced ICBMs are typically MIRVed). I don't have access to the data but it's reasonable to assume that the "most common actual event" is in fact reentering ICBM RVs on a suborbital trajectory. The last two spacecraft reentering from orbit that I know about were Stardust from heliocentric orbit and a Soyus capsule returning astronauts from the ISS. Egg plant 04:54, 7 May 2006 (UTC)

Considering how long the article is and how the big list of terms breaks up the narrative flow, I've split it off into Glossary of atmospheric reentry. Bryan 01:23, 6 July 2006 (UTC)

Heights

This article has so much technical information but is missing basic information such as heights and speeds. Where does peak heating occur.. at treetop level? -Rolypolyman 14:50, 17 July 2006 (UTC)

Yes; it can do. There's an equation for it; for some bodies the peak heating is a ground level (or below).WolfKeeper 23:16, 21 July 2006 (UTC)

i put it inhere, 'speeds and heights' ,in 'PICA' the article says:" (For reference, the Stardust reentry was faster than the Apollo Mission capsules and 70% faster than the reentry velocity of the Shuttle.[original research?])" how can that be original research? these facts are public, and it is pretty sure nasa bragged about it during the execution.24.132.171.225 (talk) 01:47, 3 October 2009 (UTC)

Individual astronaut re-entry systems and Reference Desk question

Could those who wrote this article please have a look at the Reference Desk question here:

• Wikipedia:Reference_desk/Miscellaneous#Free_fall_from_space

If anyone here could answer the questions over there, that would be great. Carcharoth 11:49, 14 December 2006 (UTC)

Expanding this article

Also, I found references in the article to less conventional astronaut re-entry systems such as the MOOSE and FIRST systems:

• Atmospheric_reentry#Non-axisymmetric_shapes

Could someone expand this section to include links to Rogallo wing, Paresev and also try and cover (or at least link to) the material in this astronautix article? I might try and do this myself, but hopefully someone who wrote this page will do a better job of it. Thanks Carcharoth 11:49, 14 December 2006 (UTC)

Secrecy controversy

There is a lot in this article about the supposed effects of secrecy and of what was secret at one point and etc. This should all be cited — as it is it verges on unsubstantiated polemic. It'd be very interesting if all of it were true but we need to actually cite that — there is a lot of junk out there on technologies which have supposedly been supressed by secrecy, and we need to have rather rigorous standards here. An article by someone alleging said secrecy hampering this work would be fine. --24.147.86.187 02:14, 12 January 2007 (UTC)

How do you cite this? Talk to any aerospace engineer about the effects of International Traffic in Arms Regulations (ITAR) on the American aerospace industry and he'll give you an earful. Do you know that formerly declassified documents have been reclassified? Formerly confidential NASA TM-X documents were declassified in the mid-1970s but have since been reclassified as "unclassified/limited". "Unclassified/limited" means that it is illegal for this information to be disclosed to non-US citizens. This same information could have been legally viewed and photocopied by non-US citizens in the 1980s. Also a new document can be declared ITAR if old information is recombined in a way that an ITAR censor finds questionable. Would an ITAR censor find this Wikipedia article objectionable? ITAR information may not be disclosed to non-US citizens.

Nations who have developed successful reentry

According to [1], only four nations have actually completed orbital reentry successfully; could we get some mention of this in the article? Night Gyr (talk/Oy) 02:24, 23 January 2007 (UTC)

A problem I see is, that the article is mixing up "manned orbital reentry" and "unmanned orbital reentry". While it's true that US, Russia, and China have recovered "manned orbital reentry craft", what India did is the recovery of an "unmanned orbital reentry craft" which has already been done by Japan (on May 30, 2003) and probably EU earlier than 2003. India's space program is aimed at a manned mission by 2014 and I don't really see any technological reason that India can fail to archieve this goal, still it's a bit premature to claim the "fourth nation" status. --Revth 03:08, 23 January 2007 (UTC)

Which spacecraft for japan? I can't find any entry for it. Night Gyr (talk/Oy) 03:20, 23 January 2007 (UTC)

ah got it [2]. Unmanned Space Experiment Recovery System Night Gyr (talk/Oy) 03:21, 23 January 2007 (UTC)

Yes, that's the one. The number of nations should be still less than ten though, as recovering is far more difficult than simply shooting up.--Revth 04:52, 23 January 2007 (UTC)

All I;m finding for ESA is Atmospheric Reentry Demonstrator, which is suborbital. Night Gyr (talk/Oy) 04:57, 23 January 2007 (UTC)

The Atmospheric Reentry Demonstrator (ARD) didn't get very hot and flew a boring trajectory (it was essentially ballast for an early Ariane V test launch). ESA did build the Huygens atmospheric probe that landed on Titan. NASA helped out a bit (behind the scenes) with Huygens. Never the less, Huygens was a significant technical achievement that should have been a major source of pride for the Europeans (most Europeans probably never heard of it). Egg plant 05:19, 25 January 2007 (UTC)

ARD was not boring, it was a guided reentry, and demonstrated significant cross range and guidance precision. A ballast has generally no GNC or attitude control thruster. It seems to me a technically more significant achievement than Huygens which was purely ballistic, therefore relying purely on precision of injection, design of the TPS and of the descent and landing system. Hektor 16:37, 23 October 2007 (UTC)

ARD was essentially a scaled down Apollo Command Module (CM). The basic CM design dates back to the late 1950s. NASA went with the CM mainly because it was conservative (a spherical section) and easy to analyse by guys having only sliderules. ESA took the old CM design, scaled it down and flew it on a trajectory where the heating was so low that there was little or no ablation in the TPS and no significant real gas effects. All ARD really demonstrated was the control laws used for its lifting trajectory could work in an actual flight. However those control laws are all in the open literature as is most of CM's technology. ESA demonstrated nothing new with ARD other than they could read old NASA tech reports and use the technology for a far less demanding test flight (the CM was designed for lunar return). If ESA had flown a HOTOL or X-38 lifting body vehicle then I would have been impressed. Again, Huygens was a genuine technological triumph for which Europe should feel significant pride. The main technological reason Huygens was important is that Titan has methane in its atmosphere. The methane causes significant amounts of CN to be produced in the shock layer. CN is a very strong radiator. The radiative heat flux experienced by Huygens and the TPS material response was a huge unknown. Huygens advanced our knowledge concerning the technology of atmospheric entry (not boring). Egg plant 01:55, 11 November 2007 (UTC)

You see, this is why talk pages are better than the articles... :-) Carcharoth 02:00, 11 November 2007 (UTC)

Carcharoth, Could you please help monitor the "Atmospheric Reentry" article? I ignored it for a few months, came back and found that it had been significantly corrupted. I undid most of the damage but it's disturbing that someone needs to constantly watch this article to keep it from being corrupted. I guess this sort of errosion must be taking place all across Wikipedia. Egg plant 07:30, 11 November 2007 (UTC)

I can try and keep an eye on it, but I'm not really the best person to ask as (a) my watchlist is large and disorganised so I'm likely to miss changes to this article; and (b) I don't have the technical expertise you obviously do, so I won't know what to do with anything other than obvious vandalism. There should be places you can ask for this sort of thing though. One thing that might help is if it ever got something like featured status. That can attract more people to watch it and keep it in good condition. As I say, I try and keep an eye on it, but probably only every couple of weeks or so. Carcharoth 09:55, 11 November 2007 (UTC)

Thank you. I think featured status might be a mixed blessing because it would attract vandals and screwballs. I think "GA" status would be good enough and leave it at that. Perhaps you could use your influence to nominate this article for "GA" status? Egg plant 20:38, 11 November 2007 (UTC)

Article Title

It seems to me that the title should be "Atmospheric Entry". Reentry implies that the vehicle left the planet it is entering, which is clearly not the case with vehicles entering the atmosphere on Mars, Venus, or any other planet. The difference is small I know, but it is not trivial. anonymous6494 21:49, 23 January 2007 (UTC)

Most of the time, it's coming back to Earth after having been launched from here. There are a few exceptions (the Venus and Mars landers; Galileo and Huygens at Jupiter and Titan), but almost all atmospheric entries are re-entries. It wouldn't be bad to have a redirect from "Atmospheric entry" to here, but this is the most common usage in the field (and I do some spacecraft design and re-entry work... not full time, but I've designed entry vehicles). Georgewilliamherbert 21:52, 23 January 2007 (UTC)

The issue of "entry" versus "reentry" was debated ad nauseum by the ding-dongs who formerly edited this article (I'm glad they got bored with Wikipedia and left). They were more concerned about semantics than getting their facts right. I deleted all of that nonsense many months ago. Egg plant 07:29, 24 January 2007 (UTC)

Be nice... Georgewilliamherbert 08:02, 24 January 2007 (UTC)

Yes, of course, my apologies, must remember to be nice.... Egg plant 04:17, 25 January 2007 (UTC)

Understandable. I didn't know Ding Dongs could use Wikipedia, or even type for that matter... anonymous6494 03:08, 25 January 2007 (UTC)

Zippy the pinhead likes to eat them with taco sauce. Egg plant 04:20, 25 January 2007 (UTC)

Since there seems to be some activity on this talk page again, is it possible someone could take the challege posed in the section I posted a few sections up: #Expanding this article? I've linked the existing mention of Rogallo wing, but there is still lots of material in this article that could be used as a basis for carefully expanding the Wikipedia article. I'll add it as an external link for now, but I hope someone can do a timeline section on the history of re-entry vehicles, both planned and actual. That would be a good way to tie in the "first" dates being discussed above. Carcharoth 10:56, 24 January 2007 (UTC)

Rogallo wings have a very nasty stall characteristic which is why that particular wing isn't used anymore for hang gliding (killed a bunch of people). Most (all?) of those one man rescue reentry vehicles from the 1960s were little more than one page proposals (a single artist's conception) that never received any development funding. Also the ballute type entry vehicles may not be practical due to aeroelastic instability. People keep proposing ballutes anyway because they're sort of a "magic sword" (like skyhooks, anti-matter drives, suspended animation, etc.) for solving impossible aerospace problems (the fact that they're impractical is only a minor detail). Egg plant 04:38, 25 January 2007 (UTC)

Even a paragraph on a few of the failed or impractical proposals would be nice. Gives a bit of the history and background to the subject, to round out the technical engineering material. Carcharoth 17:33, 25 January 2007 (UTC)

Can I reissue the above challenge? Ballute is a bit short. Maybe something on the "one page proposals" could be added there? Carcharoth 02:02, 11 November 2007 (UTC)

Pictures added

Just added pictures of the Mir and Columbia break-ups during re-entry. Are there any other pictures of re-entry available? Would putting a picture of a meteorite shower, showing atmospheric entry by natural space debris, be outside the scope of the article? What about a picture of of what happens after a successful re-entry, with a return capsule parachuting down to the sea, or a space shuttle landing?

I had a look on Commons and found these:

• 
  Stardust re-entry
• 
  Skip-type re-entry trajectory
• 
  Soyuz re-entry
• 
  Design for a NASA re-entry vehicle
• 
  Space shuttle re-entry

Are any of these suitable for this article? Carcharoth 11:54, 24 January 2007 (UTC)

The picture of the Dynasoar should probably be included (The other pictures are less interesting). Dynasoar was a USAF vehicle (was to have been launched from a Titan-II) and not NASA. I don't know if a thermal protection system was ever designed for Dynasoar. NASA's Space Shuttle was partially a consequence of Dynasoar getting canned. One might argue that it was too bad the Dynasoar didn't fly before the Shuttle. The design mistakes that ultimately ruined the Shuttle program might have been discovered with the much cheaper Dynasoar and thereby avoided. Egg plant 05:04, 25 January 2007 (UTC)

You seem to be approaching this from an engineering persepctive. The Dynosoar picture shows an actual craft close up, but the actual pictures of what re-entry looks like from a distance, although they might not seem interesting, do give another perspective on the subject. And before I forget, would anyone be able to run with the idea (I think I suggested it above) for a timeline of milestones in atmospheric re-entry history. First Earth, first on another planet, first by different countries, first by different spacecraft programs, and so forth. Carcharoth 17:37, 25 January 2007 (UTC)

Actually, on second thoughts, those "bright white dot" re-entry pics are rather boring. But maybe use one of them? Carcharoth 17:42, 25 January 2007 (UTC)

I agree that the "bright white dot" pictures are not interesting. The Atmospheric reentry article already has too many pictures of "bright lights in the sky". The "skip reentry" picture is of interest but leads to a whole new line of discussion that I've started below. Egg plant 19:46, 28 January 2007 (UTC)

hi, I just wanted to ask if these kind of pictures would be useful for this article? [3] [4] I made these for university homework and would also upload the bigger versions without the copyrighted google earth globe in it. just reply here or on my talk page, if these are needed. greets, --Andreas -horn- Hornig 12:44, 17 April 2007 (UTC)

Difficult to use those really, as they have Germna on them, and it is not clera what the numbers are referring to. If you want to do fresh pictures, tailored to this article, that would be best, probably. Thanks for asking, and have a look at Wikipedia:Graphics Lab if you want to contribute other graohics. Carcharoth 16:17, 17 April 2007 (UTC)

hi Carcharoth, I will internationalize them, if they willbe needed, of course! ;) I am just to lazy to put effort in them to do a new version BEFORE it is clear, that they can be used ;). they images are right now in that way I made them for my doucument, but I have the original, layered PNGs still here and can change them really fast. the numbers will be explaned then, too, but outside the pics, so that each wikipedia can use them without have to change the language, like you mentioned before. I am just asking If they are needed inhere, because there are a lot of good pictures in here right now, but not so much pictures of reentry phases. the one, that is nearest to that is the Skip reentry trajectory.svg, but it is still here on the talkpage. I think it would be good for "newbies" to see some graphics/images, where the different phases are explained. personally, I am a "eye-guy", I can remember facts better if I have a picture of it, whether in my head of directly besides the text ;). it is just an offer for other "exe-persons". and thx for the graphics lab hint, I will definitely check it! greets, --Andreas -horn- Hornig 12:09, 20 April 2007 (UTC)

Re-entry questions

At what altitude does (the heating due to) atmospheric re-entry occur? Is it near the 100-km Kármán line, or is it at a higher altitude? 69.140.164.142 02:53, 4 June 2007 (UTC)

That depends; usually, re-entering vehicles fly a trajectory that descends. How much they slow down at what altitude depends on trajectory choices, entry angle, lift to drag ratio, and ballistic coeficient. For the Space Shuttle, see Space Shuttle Columbia disaster which gives the altitude profile for STS-107 (up to the breakup...). Entry started at 120 km and 7,200 m/s roughly; it crossed the California coast at 70 km altitude and Mach 23 (about 96% of orbital velocity of Mach 25). Georgewilliamherbert 03:08, 4 June 2007 (UTC)

Uncontrolled re-entry

What is the definition of 'uncontrolled' in this context? Skylab's re-entry wasn't random or unpredicted, and while it was in progress attitude control was in the hands of ground controllers until aerodynamic drag caused structural breakup and communication loss. 61.88.24.50 08:02, 29 June 2007 (UTC)

Fair use rationale for Image:2003 Space Shuttle Columbia disaster.PNG

Image:2003 Space Shuttle Columbia disaster.PNG is being used on this article. I notice the image page specifies that the image is being used under fair use but there is no explanation or rationale as to why its use in this Wikipedia article constitutes fair use. In addition to the boilerplate fair use template, you must also write out on the image description page a specific explanation or rationale for why using this image in each article is consistent with fair use.

Please go to the image description page and edit it to include a fair use rationale. Using one of the templates at Wikipedia:Fair use rationale guideline is an easy way to insure that your image is in compliance with Wikipedia policy, but remember that you must complete the template. Do not simply insert a blank template on an image page.

If there is other fair use media, consider checking that you have specified the fair use rationale on the other images used on this page. Note that any fair use images uploaded after 4 May, 2006, and lacking such an explanation will be deleted one week after they have been uploaded, as described on criteria for speedy deletion. If you have any questions please ask them at the Media copyright questions page. Thank you.

BetacommandBot 20:45, 29 October 2007 (UTC)

removed "This was denied by The Pentagon

removed "This was denied by The Pentagon" as the source says 'Washington' said it, and neither version is correct. If some person said this, that person needs to be identified. Buildings, cities and states are not sources. User:Pedant (talk) 04:16, 29 March 2008 (UTC)

the pentagon has featured official spokespeople before, so it can deny anything it wants in a same fashion, i think you are not right in saying 'the pentagon' can't be a source, it is actually one that yes or noes even wars.(not that i know in this particular case it did, but it seems pretty feasible).24.132.171.225 (talk) 01:59, 3 October 2009 (UTC)

Thermal Soak section

I'm not well versed in the actual mechanical construction of heat shields on vehicles, so I'm not confident enough to make this correction on my own:

If there is no air gap between the shield and the vehicle, then I would say that the term 'convection' should be changed to 'conduction'. If anyone else feels that 'conduction' would be more appropriate than 'convection', then please make the correction.

Windsmith (talk) 02:28, 2 June 2008 (UTC)

This should definitely be conduction. The energy transfers from the gas after the shock layer into the heat shield via convection. Then the energy travels via conduction throughout the vehicle and into the payload. This remark is also noted as citation needed. I'm not going to add a citation, mostly because I don't feel motivated enough to look up the source, but any text book on heat transfer or reference on the science of convection and conduction heat transfer would suffice. It's not very advanced and so is readily available. 192.12.88.2 (talk) 23:02, 29 June 2009 (UTC)

Powered Descent without heatshield

I've been looking for information on this online, but no one seems to discuss it. This may be because no current or planned spacecraft are capable of such a manoeuvre.

Basically I was interested in the principle of using a retrograde deorbiting burn to remove all of a crafts orbital velocity, so that it can then descend vertically, again using thrust to keep the velocity low enough that heat shielding is not required. Basically landing on the earth in the same way you would land on a planet with no atmosphere.

Perhaps someone with more knowledge of orbital mechanics could add something? It may not be of any interest to anyone but me of course, so I would leave it to someone more qualified to argue its notability.

It is a long way off, if it ever happens. When I modelled it using Orbiter, a full powered descent from 300km (after visiting the ISS) consumed about the same amount of fuel as a Holman transfer to Jupiter. That rather massively exceeds the delta-v budget of current craft. 78.149.108.249 (talk) 23:09, 8 July 2008 (UTC)

It's completely impractical, and even if you could do it, you simply wouldn't want to; nor is it a notable idea for the wikipedia.- (User) WolfKeeper (Talk) 00:44, 9 July 2008 (UTC)

I disagree, I think someone with the relevant knowledge should add something on this. I think it is particularly relevant when considering an orbital tether. These vessels would "re-enter" earth's atmosphere, but will not require heat shields as long as their velocity is controlled. You would be forgiven for thinking that all atmospheric re-entry requires some form of heat shielding from this article 81.154.109.136 (talk) 21:00, 21 November 2008 (UTC)

Fair enough I suppose, although I can think of at least one circumstance where you might want to do this if you could overcome the fuel requirements. This approach would allow you to land a truly massive vessel on earth, perhaps something intended for interplanetary travel. Such a vessel would be too large to effectively heatshield, and in any case the dynamic pressure of a conventional reentry would destroy it. Again, this is just science fiction right now. All I'm saying is that in 200 years I wouldn't be surprised if reentry in this fashion has its uses. 78.149.108.249 (talk) 11:53, 9 July 2008 (UTC)

I have to disagree that it has any place outside of a speculative mention within this article. This is mostly because all of the science surrounding powered descents without heatshields due involve the concept of a tethered descent. All of the science regarding this topic is contained within the topic of the space elevator. This includes the material concerns, robotics, energy transfer to power the climbers, etc. Even more notable is that all the talk on this topic mostly concerns ascension, ie placing satellites into orbit. Very little is concerned about or researched on the topic of descension with a space elevator. Mind I call it a space elevator because this is the recognized term used to describe it within technical circuits, including NASA and other research institutions. I agree that the idea is a possibility within 200 years for a powered descent without heat shielding, but as of now, there is simply no research, talk or even speculation on any project to even look into it. Thus, a mention at best within the article. 192.12.88.2 (talk) 23:09, 29 June 2009 (UTC)

Lets say that by applying vertical up/downward thrust plus forward backwards thrust a cool re-entry can be attained, has this approach been tried? MX -- AGS -- --Dagofloreswi (talk) 09:53, 11 February 2010 (UTC)

Just consider how much propellant you'd need, and the cost of carrying it with you. It's patently absurd, and that's why you wont find anyone who's tried it. -- 99.233.186.4 (talk) 15:39, 24 February 2010 (UTC)

Notable atmospheric entry mishaps

Deleted "Vostok 1 — The service module failed to detach for 10 minutes. Lone cosmonaut Yuri Gagarin survived."

Detachment failure was a common problem for almost all Vostok and Voskhod-class spacecrafts, even the Soyuz. It was a minor one, since the wires that usually didn´t disconnect were always burnt by re-entry. Plus, there was no further complications associated with them. Therefore, none of the Vostok, Voskhod or Soyuz detachment problems qualify for "notable atmospheric entry mishaps".

I will leave the other Voskhod and Soyuz entry that present the same problem, for debate.—Preceding unsigned comment added by Unsterblich (talk • contribs) 05:49, 3 September 2008 (UTC)

Added Space Shuttle Challenger Disaster. DunMifSys (talk) 21:17, 11 March 2009 (UTC)

And removed. Space Shuttle Challenger exploded before it even left the atmosphere, so there was no atmospheric reentry. Therefore it doesn't belong in this list.

Odd claim

Among the unreferenced oddities in this article, there is the line: "Amongst aerospace engineers, AMaRV has achieved legendary status alongside such technological marvels as the SR-71 Blackbird and the N1 rocket". Would that be the Soviet N-1 moon rocket that never made it beyond the atmosphere? To quote the N1 article: "It was underfunded, undertested, and started several years after the Saturn V; all four launch attempts failed, and the project was officially cancelled in 1976." Are aerospace engineers very easily impressed, or am I missing something? Davidelit (talk) 06:46, 12 September 2008 (UTC)

Personal points of view in footnotes

There seems to be a misunderstanding reflected in this article about WP:NPOV. Neutrality applies equally to footnoted text and article text, but the footnotes for this article reflect considerable ... non-neutrality. For example, "John J. Martin's book was the first and arguably the best in the open literature about designing reentry vehicles. In his book, Martin showed an incredible depth and breadth of knowledge. Unfortunately, this book has been out-of-print for decades but is sometimes available second hand through the Internet." I question whether this meets our encyclopedic standard. (sdsds - talk) 06:46, 19 February 2009 (UTC)

(Two years later) I've removed these book reviews. They clearly have no place here.. too bad it took this long. Mlm42 (talk) 06:19, 4 January 2011 (UTC)

Friction

Changed the one bit on friction, said something like 'contrary to popular belief, the heating isn't caused by friction' to now state not caused by direct friction upon object, but rather friction between air molecules as they get compressed. So fyi, popular belief is correct, it's friction, just the friction between air molecules as they get smashed together, rather then friction of molecules sliding/rubbing past the object. Still friction. 69.151.50.116 (talk) 13:40, 19 March 2009 (UTC)

I have to disagree. Your misinterpreting basic fluid mechanic fundamentals. Friction is related to an increase in entropy associated non conservative forces. Gas can be heated up simply by being compressed isentropically, without any friction occurring in the gas at all. Proof of this is that a gas can be compressed and then uncompressed, recuperating nearly all of the original pressure and volume. The temperature will certainly increase while it is compressed, but if friction was the active process for this, you would be unable to recuperate nearly as much of the original volume and pressure. Remember, P=rho *R*temperature is the ideal gas equation. It predicts a temperature increase yet actually assumes that no friction at all takes place. When discussing compressible flow, the temperature increase across the shock wave in front of the reentry vehicle as it reenters the atmosphere is due to the same principle. Even if the air shooting across the shock wave is modeled as a completely isentropic process, the temperature increase of the gas can be massive. In fact, it is greater than the heating of the reentry vehicle by friction between the gas and the vehicle by far. True, shock waves are not isentropic processes and there is frictional heating occurring within them. But the compressional heating is by far greater in magnitude and is not in any way related to frictional processes. Finally, the gas transfers energy to the reentry vehicle, inducing heating, by both frictional and non frictional means. Also, again, it can be verified in any wind tunnel test that the shear stresses on the reentry vehicle are far lower than the normal pressure levels. This indicates that the way the hot gas transfers its energy to the reentry vehicle, essentially heating it up, is by far determined by the non frictional processes. Altogether, this means that the heating of the air molecules as they get smashed together is in fact, not friction and that friction is not the prevailing heating method for a reentry vehicle. 204.52.215.1 (talk) 18:30, 17 April 2009 (UTC)

New Technical Information

I know that we don't want to go overly technical on this article but some general rules of thumb should be addressed. First off, I like the article for why the heating rate is inversely proportional to the drag coefficient and think the section detailing the blunt bodied RVs is good. However there is a rule of thumb for determining heat rates that is much simpler to follow and can explain it better to those not an engineer for the military or NASA. Assuming that you disregard the laminar to turbulent boundary layer transition during reentry, then the heating rate for a vehicle is roughly proportional to the local density of the atmosphere multiplied by the cube of the RV's velocity at that altitude. (rho*V^3) Now, the density of the air is also known to increase exponentially as the RV approaches the planet's surface. (rho=density_at_sea_level*e^(m*g*h/(k*T)). This may seem overly technical but I'm just making a point right now. Altogether, this means that if you want your RV to survive reentry then it better lose most of its speed in the upper atmosphere before the density starts increasing rapidly or it'll be destroyed. Now keep in mind that the drag force is proportional to (cD*rho*V^2). Thus, a large cD will slow you down in the upper atmosphere and allow reentry. Now I know this is a relatively dumbed down explanation but it can give some people a way to think about it. I will comment that citing this is particularly hard as this has arisen from textbooks and conversations with experts in aerodynamic design and supersonic flow that I have had over the years. Thus I can't at this time pin it to a single source and don't feel motivated to track one down. If it never leaves the discussion section that'll be too bad but I'm just putting it out there.

Another thing severely lacking in this article is laminar vs. turbulent boundary layer affects. This is critical as it determines RV shape design and is inherent in even the trajectory of the shuttle's reentry. Every RV is surrounded by a boundary layer that changes shape and characteristics with the RV's speed, mach number and other parameters. If the boundary layer is laminar then much less heat is transmitted to the RV than if it is turbulent. The boundary layer will eventually transition to turbulent on the shuttle as it slows down but it must stay laminar until the shuttle has decelerated to lower than about Mach 17. (This may be Mach 13.) It starts reentry at Mach 35. If transition occurs before this the shuttle will be lost due to increased heating conditions. Note that when transition occurs, the heating rate increases enormously and you had better be at a slow enough speed to mitigate this or the RV is lost. The source of this information is several engineers working at NASA's Langley research center in the aerothermodynamic department. They do shuttle support in the form of wind tunnel testing. As a side note, according to these engineers the damage to Columbia's leading edge caused a transition to turbulent flow at about Mach 19 if my memory serves me right. The official cause of destruction on Columbia was superheated air rushing into the wing below the heat shielding, effectively destroying the shuttle. Due to the high transition mach number, even if no air had entered the wing, it would still have been destroyed. This is why this inclusion is important regarding turbulent vs. laminar flows. 192.12.88.2 (talk) 07:40, 4 May 2009 (UTC)

Regarding your first point about density, I think that's a great contribution. It starts to answer the question 'why is the heat load during reentry greater than launch?'. There's some discussion on this here http://www.physicsforums.com/archive/index.php/t-149933.html but your post is better. Mango bush (talk) —Preceding undated comment added 03:24, 18 November 2009 (UTC).

Could spent stages be added to the small disposal section?

The article mentions satellite disposal. Could rocket stages be mentioned? I do note the Apollo XIII illustration. Thank you. —Preceding unsigned comment added by Fotoguzzi (talk • contribs) 09:54, 14 July 2009 (UTC)

angle of re-entry

Where can I find information on the angle of re-entry of spacecraft, on who calculated the angles, how and when? --Agesworth (talk) 08:15, 1 January 2010 (UTC)

I think(?) the concept of entry angle for a reentering spacecraft was first published by Dean Chapman, refer to Note 23 on the main Atmospheric reentry page. Entry angle is sometimes referred to as "gamma", or Flight Path Angle or FPA. I like to call it "gamma" but most people seem to prefer "FPA". Gamma is simply the angle between the vehicle's velocity vector and the local horizon at that instant in time. However note that the velocity vector is different depending upon its frame of reference, i.e. it can be atmosphere relative or inertial. When people are being precise they may write FPA[relative] or the letter gamma with a "rel" as a subscript. More often than not, people are NOT precise and the reader is left scratching his head wondering which frame gamma was referenced to. By the way, Dean Chapman was an incredible genius. As a pioneer in the technology of atmospheric entry, Chapman was in the same league as Harvey (H. Julian) Allen and Al Eggers (all three guys worked at NASA Ames during the early days of the Space Program). Egg plant (talk) 07:34, 9 February 2010 (UTC)

attempt to rescue deleted section?

a whole section on research into atmospheric entry was deleted as original research, and while much of it looked like a personal rant, it seems a shame to remove the whole section. the following referenced claims were rescued from that text, but i'm not sure exactly where to place them. please insert into appropriate places. -- 99.233.186.4 (talk) 03:02, 2 February 2010 (UTC)

I wrote the section that was deleted along with most of the Atmospheric reentry article. I have since undeleted it. I also brought back the Galileo Probe section that some nitwit deleted. I come back about every 9 months to do general housekeeping. This is about the third time this specific section has been undeleted. One of these days someone will lock this article and my work here will be finished. Thanks for taking an interest! Egg plant (talk) 07:18, 9 February 2010 (UTC)

== Research into atmospheric entry ==

Mk-12A RV retrofitted with hafnium diboride strakes for a NASA research project (Sharp-B2).

NASA's Inflatable Re-entry VehicleExperiment (IRVE) launches.

Research into supersonic flight began at the end of the 19th century, but unsolved problems prevented progress until the Cold War, when aerodynamic ranges conducted impact tests to determine the lethality of kinetic energy weapons against the ICBM threat.

Research into atmospheric entry was and continues to be restricted because aerospace technologies can be used for civilian or military purposes (known as dual use). In fact, space systems technology has its own section on the militarily critical technologies list. Classified technical reports are unavailable to the public.

In the commercial realms, scientific research on atmospheric entry is broadly published in the US patent record, and several journals worldwide. But, those seeking historical context for this material from NASA will discover that its document retention policy may result in destruction of the information prior to its mandatory declassification, since patent-worthy technical documentation is subject to destruction after 20 years.

Citations and sources are needed

Please be sure that all additions to the Atmospheric reentry article are verifiable. Any new items added to the article should have inline citations for each claim made. As a courtesy to editors who may have added claims previously, before Wikipedia citation policy is what it is today, several of the existing unsourced claims have been tagged {{citation needed}} to allow a bit of time for sources to be added. N2e (talk) 17:12, 9 February 2010 (UTC)

Ideal vs 'Real' Gas Behavior and Engineering

The article states the following: "Perfect gas theory is elegant and extremely useful for designing aircraft, but assumes the gas is chemically inert. From the standpoint of aircraft design, air can be assumed to be inert for temperatures less than 550 K at one atmosphere pressure. Perfect gas theory begins to break down at 550 K and is not usable at temperatures greater than 2000 K. For temperatures greater than 2000 K, a heat shield designer must use a real gas model." Wouldn't the claims, assuming they are true or reasonable approximations, be dependant upon other variables rather than temperature that are at least as important? Pressure of the gas, namely, is what I had in mind. Given the context of this article, it seems plain that the pressures will be wildely different under different situations and that even assuming this was bassed off of 1 atm on the surface being presumed (something that cannot be presumed) it is nevertheless an incorrect statement. I would change it but I'm not familiar with the physics/engineering and am sure someone else could write this better than I while perhaps stating more clearly what the above-quoted section is getting at in the context of actual examples.--Δζ (talk) 09:22, 3 June 2010 (UTC)

Magnetic heat shield

There are afew articles on the net that seem to point to a Magnetic heat shield being developed, I was wondering if this should be discussed and maybe added to the Wiki Article?

One of the Articles about it, googling "Magnetic Heat Shield" comes up with afew, some just seem to be exactly the same text on different sites. http://www.flightglobal.com/articles/2009/11/24/335327/magnetic-heat-shield-test-could-use-russian-launcher.html

MizunoJames (talk) 19:42, 6 August 2010 (UTC)

Need to add info on Avcoat

It was the re-entry shielding used on the Apollo CM and is going to be used on the Constellation(?) CM.

http://www.nasa.gov/home/hqnews/2009/apr/HQ_09-080_Orion_Heat_Shield.html --Craigboy (talk) 05:45, 21 October 2010 (UTC)

AVCOAT 5026-39

Does anyone know much about AVCOAT 5026-39 as a re-entry heat ablator material? I just heard of it today. Did a search and found that Wikipedia has a (very poor) article on it. If it is notable and verifiable, then perhaps it should be mentioned in the Atmospheric reentry article. Cheers. N2e (talk) 02:04, 17 November 2010 (UTC)

This might be what you're lucking for. Apollo Experience Report - Thermal Protection Subsystem (Jan. 1974) --Craigboy (talk) 13:38, 25 November 2010 (UTC)

Yeah, looks like a good source. Thanks for your work on improving the Avcoat article (AVCOAT 5026-39). N2e (talk) 14:13, 25 November 2010 (UTC)

I have stubbed out a summary section on AVCOAT and added it to this Atmospheric reentry article. Please take a look and improve as needed. N2e (talk) 15:37, 2 January 2011 (UTC)

Inflatable Re-entry Vehicle Experiment (IRVE)

Article has an image of it being launched but never explains much about it. This link could be used to add some more info if it's relevant enough. http://www.nasa.gov/topics/aeronautics/features/irve.html --Craigboy (talk) 12:01, 25 November 2010 (UTC)

I have added a couple of paragraphs to the article. The image yet needs to be moved to the section adjacent to the text. N2e (talk) 21:00, 2 January 2011 (UTC) UPDATE: moved the image to be adjacent to related text. N2e (talk) 06:10, 4 January 2011 (UTC)

Desire to create spread sheet of heat shields

First column would include country, second would be the name of the heat shield, third would be missions used on. If there's not enough room in article than it may need to be on another page. Information on foreign heat shields is desirable especially the Soyuz and the Shenzhou.--Craigboy (talk) 09:23, 26 December 2010 (UTC)

Biased in favor of spacecraft

The intro says that "atmospheric reentry" applies to natural objects as well as spaceflight, but the entire article beyond that first paragraph deals solely with man-made artifacts. There is a lack of any balance in this article as it does nothing to cover natural objects entering the atmosphere. As meteors are one such much studied natural phenomenon, and the KT impact another, along with Shoemaker-Levy-9, this seems very lacking in information. 184.144.161.173 (talk) 13:01, 2 January 2011 (UTC)

How about instead we change the name of the article to something like "Atmospheric reentry of manmade objects" or "Atmospheric reentry shielding"?--Craigboy (talk) 07:50, 10 January 2011 (UTC)

Perhaps I'm missing something but natural objects generally don't reenter... ChiZeroOne (talk) 08:07, 10 January 2011 (UTC)

With the article having been renamed (see sections below) from Atmospheric reentry to Atmospheric entry, it would seem to have eliminated the scope limiting that happens from a poor title. With no additional discussion going on here, I'm going to remove the NPOV tag on the article. The prose will grow over time as editors choose to participate in improving the article in the great spontaneous order of Wikipedia. Cheers. N2e (talk) 05:48, 16 February 2011 (UTC)

I don't entirely agree.. this article doesn't appear to violate WP:NPOV.. it's written neutrally, it just doesn't have a section on "Atmospheric entry of natural objects". I agree it should be expanded, and clarified, but I'm not sure about it violating NPOV. Mlm42 (talk) 05:55, 16 February 2011 (UTC)

Mlm42. I can't quite tell what or who it is that you "don't entirely agree" with. I too think the article is fine now; i.e., it does not violate WP:NPOV; that's why I removed the POV tag. Do you disagree with that? Or do you disagree with something said by a previous commenter? Or what? Cheers. N2e (talk) 19:59, 16 February 2011 (UTC)

Oops, sorry, I misread your comment. I saw the tag was still there when I started writting my comment, and I thought you were saying it should stay. My bad. Mlm42 (talk) 20:39, 16 February 2011 (UTC)

No worries Mlm. In fact, now that you weighed in on the topic, we can say we have a clear consensus on the removal of the tag, rather than just one lonely editor (me) removing based on a perceived take on the situationg. Good working with you! N2e (talk) 21:03, 16 February 2011 (UTC)

merge from Ballistic reentry

It appears Ballistic reentry should be merged into this article. This amounts to adding a definition of "Ballistic reentry" somewhere in this article. Mlm42 (talk) 05:51, 4 January 2011 (UTC)

• Support the merge. OR AfD delete the ballistic re-entry article as not a single source is used to back up the apparent original research. N2e (talk) 06:02, 4 January 2011 (UTC)
  • Google reveals that some sources use the term; for example the BBC news story here.. no point in deleting. Why delete when you can merge? Seems like a waste of time. Mlm42 (talk) 06:08, 4 January 2011 (UTC)

• Oppose, there are a number of different methods of atmospheric reentry; ballistic, aerodynamic lift, and lifting bodies etc. There are even different methods of accomplishing those methods, i.e Skip reentry. Each one has the potential to be expanded into a substantial article. ChiZeroOne (talk) 08:04, 10 January 2011 (UTC)

• Oppose per ChiZeroOne. --Whoop whoop pull up ^{Bitching Betty | Averted crashes} 22:58, 17 July 2011 (UTC)

Europe and atmospheric entry

• European Union is listed as having achieved Unmanned Orbital Reentry, I'd like to know for which vehicle. Because if this assertion is based on the Atmospheric Reentry Demonstrator, please remember this was a suborbital vehicle. Or do you think of Huygens ? The probe was carried by a US spacecraft Cassini so it is not fully a European project. The second point is that the European Union and ESA are two different things. For instance Switzerland and Norway are part of ESA. Hektor (talk) 08:04, 1 March 2011 (UTC)