Talk:Air-augmented rocket

Untitled

somebody oughta put a nice article stub for "Ramrocket; Please See "Air Augmented Rocket."

Prometheuspan 00:35, 3 February 2006 (UTC)

Go ahead, it's not hard to make a redirect. To see how to do it, click on a redirect, and then when you get to the target page, click on the link at the top. You can then start to edit it and you'll get the source. That will show you how to do it.

For example go to Space Shuttle. WolfKeeper 04:04, 3 February 2006 (UTC)

Ducted rocket

I've removed the reference to integral rocket/ramjets and ducted rockets from the "also known as" list at the start of this article.

The integral part of integral rocket/ramjet refers to the fact that the solid-propellant booster is integrated within the ramjet combustion chamber. Otherwise it's just a normal ramjet. This is a more efficient packaging solution than external tandem (e.g. Sea Dart) or wraparound (e.g. Bloodhound) boosters.

A ducted rocket is just a type of solid propellant ramjet. A solid propellant gas generator exhausts a hot fuel-rich gas through a nozzle into the ramcombustor where it burns in the compressed air from the intakes. The gas generator exhaust is fairly low velocity and does not produce enough thrust by itself to operate as a rocket. A ducted rocket produces little or no thrust statically or in a vacuum. A throttleable ducted rocket, sometimes known as a variable flow ducted rocket, is the propulsion system on the European BVRAAM Meteor, which recently began flight tests.

I admit that the nomenclature is somewhat confusing as the air augmented rocket, or ejector ramjet, is effectively a rocket in a duct.

I think that it would be better if the differences between these engines was covered here, it presumably isn't covered elsewhere. So are you saying that integral rocket/ramjets don't choke on the main nozzle at low airspeeds, and hence give negligible thrust? So far as I am concerned this article should talk about all airbreathing jet engines with supersonic combustors, but YMMV.WolfKeeper 19:42, 24 August 2006 (UTC)

Nomenclature for this whole breed of "air-augmented" concepts is usually rather arbitrary and vague and largely dependant on the author who coined it due to the sheer number of possible variations in configuration. In my opinion, the concepts can effectively be split into two groups - ejector rockets and ejector ramjets. These can be defined as a "rocket in a duct" and a "rocket in a duct with secondary fuel injection" respectively. This actually makes sense as any time one refers to their work on "ducted rockets" or "air-augmented rockets" or "shrouded rockets" or any other of the substantial number of terms, requires a detailed description of the configuration due to the lack of clear definition. The name actually therefore serves no practical purpose and isnt worth debating... AJC 152.78.62.182 (talk) 17:08, 8 February 2008 (UTC)

P.S. I do not mean to aimlessly criticise here, I do actually intend to make my own (fully referenced!) contributions to this page when I have the time to do it as I think far too much is disputable when considering recognised literature. Having said that the confusion that arises from this area is completely understandable, as the literature itself is extremely confused and haphazard as I alluded to in the previous post. AJC 152.78.62.182 (talk) 17:13, 8 February 2008 (UTC)

Around 1945, the Convair XF-92 also had a myserious prototype that used something of this sort. It's been variously described as a ducted rocket, a "turbo rocket", etc. Would be interesting to know what they were doing. DonPMitchell (talk) 07:05, 24 June 2012 (UTC)

Effectiveness

This entire section needs to be rewritten with references and support. I lack the time presently to complain as thoroughly as I did for downsides, but the section is just as bad. Tirgaya 20:42, 24 February 2007 (UTC)

Downsides

I removed the phrase, "Therefore ramrockets make relatively poor rockets" because the simple conclusion is unsupported. In fact this whole section may be empirically refuted by Gnom.

So far as I am aware, Gnom didn't actually give any performance advantages, it just allowed the vehicle to be more compact; by using the atmospheric oxidiser. That meant it could fit onto a particular truck. But the cost was no better, and probably worse, and so the project died with the guy trying to promote it.WolfKeeper 19:59, 24 July 2007 (UTC)

Well I guess that depends on what you call "performance advantage"... certainly the fact that it had the same performance for half the weight seems like an advantage to me... Maury 21:53, 24 July 2007 (UTC)

I'm sure it had much higher dry weight though, and dry weight costs ~$1000/kg, whereas oxidiser costs about $1/kg. So it probably in fact cost more and had the same delta-v. Doesn't exactly sound like a win to me, YMMV.WolfKeeper 01:13, 25 July 2007 (UTC)

The Downsides section also makes several unsupported assertions. Where is the evidence for the notion that the air ducting needed is itself 5 to 10 times the mass of a rocket with similiar I_sp or thrust? Why is it relevant that the air intakes are hard to design? Aren't all rockets? The claim that the "airframe" must be designed around the intake is false prima facie as evidenced by Gnom and GTX. The claim that thrust runs out as the system rises out of the atmosphere ignores the fact that this isn't an entire propulsion system, but rather an optimization of an existing system... namely rockets. Tirgaya 20:42, 24 February 2007 (UTC)

Huh? You don't think the structure of tanks+ducts weighs more than the structure of tanks? You've never heard of the difficulties that the designers of Concorde, Valkyrie, and the SR-71 had with their inlets? (Not to mention the logical fallacy that the existence of a large something is proof that it didn't need to be designed around a smaller something that forms an integral part.) 24.16.164.253 19:04, 24 July 2007 (UTC)

But it doesn't say they weigh more than the tanks. It says that the ducting alone weighs 5-10x the weight of the *rocket*. As written that sounds like it says the ducting weighs 5x as much as the rocket's wet mass (fuel included) which is obviously false. Even if you mean dry mass that's including the weight of all the crap like engines, fairings/payloads etc..

And it says compared to a rocket with a similar thrust. That makes the comparison itself fundamentally confused since thrust is an instantaneous measure. Is that a rocket that makes that thrust for only a millisecond? It can't be total impulse either since, as ramjets are in some sense examples of such rockets, it implies that every ramjet in a missle could be replaced with a solid or liquid motor rocket with 5-10x total delta-v). Likely what was meant was that the ducting weighs 5-10x the dry mass of the tanks for a rocket with similar total impulse and specific impulse.

I'm deleting that statement because it's not only not sourced but, as written, pretty confused. If someone wants to reword it so it makes sense they can add it back. Peter M. Gerdes (talk) 02:52, 22 May 2023 (UTC)

To be honest, I do agree with you that this section (and frankly, the rest of this article) is woefully inadequate with regards to unsupported assertions. I would like to see evidence for the weight impact of the ducting as I have certainly not come across this figure and 5-10x the core rocket mass seems somewhat large. Structurally, this might be true, but a rocket isnt just an empty container - you need to account for propellant in this evaluation. I DO find it difficult to believe that that ducting weighs 5-10x more than a fully loaded rocket (understatement). It is however completely relevant that intakes are hard to design, all rockets do NOT have intakes. Intakes increase the complexity by orders of magnitude particularly at high supersonic and hypersonic velocities! At these speeds the main driver for the entire vehicle design is most definitely the intakes. Related to this point however, and also you last point regarding thrust depletion - is connection between ejector technology and the flight envelope. The air-augmentation certainly does not provide benefits over the entire flightpath but this in itself is a supremely complex optimisation exercise. AJC 152.78.62.182 (talk) 17:34, 8 February 2008 (UTC)

History

This statement regarding Gnom makes the large part of this section - does anyone actually have any SOLID references for the details regarding this? Firsty, I ask out of interest as verifiable information regarding this design would be invaluable to me. But more importantly, one internet web site which is referenced basically by any mention of this technology on the internet (as far as I can make out) is hardly sufficient as a source, at least as strongly worded as this section is. I know that the website in question seems to be reasonably well informed and supposedly referenced but as I can not seem to find the reading materials he points to I really can't take it with anything more than a pinch of salt. If no-one objects to this or counters it in the near future I will probably alter the wording of this a little to reflect the less-than-verifiable details. AJC 152.78.62.182 (talk) 17:23, 8 February 2008 (UTC)

Gnom was never flown, according to astronautix.com. If you're going to get into unbuilt projects, then the first design draft of the Convair XF-92 had a ducted rocket powered by nitromethane, around 1945 or 1946. DonPMitchell (talk) 21:57, 4 April 2013 (UTC)

PDE

I was looking at a new type of engine being developed (pulse dentonation engine) and I was wondering...

Would it work for an air argumented rocket? Are there any benfits of using PDE over jet?

Found out there is a design for a Pulse Dentonation Rocket (Patent given in 1992) that makes use of oxygen in the atmosphere as well as LOX contained in a tank aboard the rocket.

Would like to add a description to this page next week (08/10) unless there any disagrements —Preceding unsigned comment added by 195.229.236.250 (talk) 16:40, 8 October 2007 (UTC)

Actually there are reasonably well known advantages for the ejector principle to be applied to designs utilising unsteady primary drivers (such as a PDE) as the benefits are much greater than those for steady primary drivers (such as a jet or rocket exhaust). It's related to the enhanced mixing due to the pulsed flow. So yes, there are advantages to using pulsed flow over steady flow BUT this does not make a better candidate for the air-augmented _rocket_. The subject of this page is just that, augmentation of the core rocket performance by using captured airflow. Replace the rocket and it is a completely different animal. AJC 152.78.62.182 (talk) 16:57, 8 February 2008 (UTC)

Liquid rockets instead?

The article gives all its focus to a solid rocket with a surrounding ejector/nozzle thing that intakes air, is compressed/heated, and then expanded along with the normal rocket thrust. But it doesn't seem to consider liquid rockets in place of the solid core. This is possible right? And wouldn't it give even higher Isp? DrZygote214 (talk) 23:19, 5 October 2014 (UTC)