Q & A about Aircraft, Armor, Weapons , Transport and Ships

[McColm]

This may have been covered before, but is always worth updating from time to time as more data becomes availible.

Question 1)
The Armstrong Whitworth Apollo was fitted with Mamba engines, in an early photo four-bladed propellors are on the inner engines and three-blades on the outer. Would this improve performance, if fitted on another four engined aircraft?

[sandiego89]

I don't think there is a universal formula indicating this would beneficial.  Each aircraft is unique, and if I understand it correctly on the Apollo it was more of a stability issue, that more blades on the inner engines helped improve, so perhaps not just a "performance" increase in the traditional sense, but perhaps better specific thrust at certain settings. Another aircraft with differing propellors (and differing number of blades) was the PB2 Coronado, with 4 shorter blades on the inner engines, 3 longer blades on the outers.  This was to ensure proper clearance between the blade tips and the fuselage, with the added benefit of thrust reverse for surface maneuvering. 

Plenty of aircraft do just fine with four, 3 bladed props, or four 4 bladed props (or 2, or 6, etc). 

Many factors go into choosing the propeller (and the number of blades).  Engine specs, clearance, angle, airflow, size, weight, RPM, desired flight characteristics, cooling, etc.

Having different props on the same aircraft complicates synchronization, maintenance, etc.  So unless there is a specific reason for needing different props on the same aircraft like ground or fuselage clearance, correcting a specific flow pattern, increasing thrust on a certain set for stability issues, etc I would not think the benefits would be universal.     

 

[McColm]

Thanks,
Question 2)
Has there ever been a gas turbine engine fitted to an aircraft?

Question 3)
Most airliners have the engines under the wings on pylons, some like the VC10 or Trident had a combination with engines at the rear and under the wings. Have they ever been placed at the front of the wings or just past the wings on pylons?

Question 4)
Submarines can launch missiles from under the sea, has this method been used in a jet powered sub?

Question 5)
The mission to Mars is still going ahead, have they worked out how to get back to Earth? Are there no planets closer to land on and explore?

Question 6)
I can usually hear an aircraft before I can see it and yet the speed of sound is slower than the speed of light ?

Question 7)
Digital camouflage patterns have been seen used by the USA military. Do other countries use it, or is it better than the current patterns?

[scooter]

Thanks,
Question 5)
The mission to Mars is still going ahead, have they worked out how to get back to Earth? Are there no planets closer to land on and explore?

Part 2- No, save the Moon.  Part 1, some plans have it a one way trip establishing a colony, others have a round trip, creating fuel for the lander locally

[PR19_Kit]

Question 2) Er, perhaps you could re-post that. Frank Whittle and Hans von Ohain did it a LONG time ago......

Question 3) If you look from the side many aircraft, especially large airliners, have the pylon mounted engines actually forward of the leading edge. The DC10 and 777 are cases in point.

Question 4) Are there any jet powered subs?

Question 6) You have to be looking in EXACTLY the right direction to see it, whereas the sound arrives at your ears without too much directional information.

[zenrat]

Q5.  Mars is also the planet with surface conditions closest to earth.  All the others are mostly gas, have poisonous/corrosive atmospheres, molten surfaces or are frozen balls of ice so cold it snows methane.

Q4.  Submarines are hunted with SONAR therefore the most important characteristic of any design is low levels of noise while operating.  A rocket engine (you could also use a jet but it would either need a big snorkel or a really huge supply of compressed air) would create a lot of noise as the exhaust boiled the water.

Q6.  If the wind is in the right direction you can hear further than you can see.  Your ears have better resolution than your eyes.

[pyro-manic]

2: Uhh, yes? You talk about two of them in Q.3...

4: There are no "jet-powered subs". Jet engines need air to run, something in rather short supply when under water... Submarines are nuclear powered or diesel-electric (there may be a few one-off freaks out there).

5: The proposed privately-funded "Mars One" mission is one-way only. They won't be coming back. There are no other rocky planets that are remotely reachable that are plausible targets for a manned mission. Mercury is tiny, and very close to the sun so very hot. Venus is even worse, due to it's incredibly dense atmosphere which traps heat. Earth is next, then Mars. After that there's a very big gap, and then the gas giants. Some of the moons of Jupiter and Saturn may be targets for manned missions eventually. Beyond those are the dwarf planets, which are very small, very cold, and very, very far away.

6: You can see an airliner at 30,000 feet from much, much further away than you'll ever hear it. Go and read up on how sound travels, as opposed to the way light travels.

7: Yes, plenty of countries have introduced digital camouflage patterns. Canada actually did it before the Yanks.

[KJ_Lesnick]

Is this by any chance a satire of my questions?

[McColm]

No satire intended, genuine questiones that have yes or no explained in words that I can understand

[McColm]

Question
Has anyone considered using a flying boat/seaplane in the AEW role?
As a Whiffer the Shorts Sunderland springs to mind as a possibility, as the rotor dome can be mounted above the fuselage or fixed array .

Question 9)
The USAF and the USNavy deploy dedicated EW aircraft. So how come the RAF and the Royal don't follow suit? There was a Canberra EW training aircraft used but no dedicated EW Canberra deployed.

[Old Wombat]

2) gas turbine = jet ... you've probably noticed quite a few of them flying around recently.

3) Kit answered this one.

4) I don't know if any exist (I doubt it) but you could have electric motors running turbine blades to propel a sub but, as stated, a jet engine needs lots of air & runs very hot, with a lot of exhaust gases to get rid of.

5) Basically, the answer is "yes" - Venus. Venus, however, is not conducive to any length of survival for Human explorers (Venus), whether in suits or not. (minimum Earth-Venus distance = 43,160,000 km; minimum Earth-Mars distance = 52,600,000 km) The distance to Jupiter is sufficiently great that, even at its closest, it's further away than Mars at its most distant.

6) Again, Kit answered this one.

7) No idea, see pyro-manic's answer.

Still working on 8 & 9.

[PR19_Kit]

8] By the time that AEW had reached a practical level of operation flying boats were already on the way out. The Grumman TBM-3W Avenger was the first production practical AEW aircraft and that entered service in mid-1945. The USN used big scanners inside airships after that, before both the USN and USAF took delivery of the Super Connie AEW aircraft in the early 50s. By then the only flying boats in service were the USN's Marlins and the RAF's ancient Sunderland 5s.

9] Perhaps the RAF figured that the pylon mounted underwing pods, the BOZ109 for example, were good enough for their planned operations?

[jcf]

Question
Has anyone considered using a flying boat/seaplane in the AEW role?
As a Whiffer the Shorts Sunderland springs to mind as a possibility, as the rotor dome can be mounted above the fuselage or fixed array .

Question 9)
The USAF and the USNavy deploy dedicated EW aircraft. So how come the RAF and the Royal don't follow suit? There was a Canberra EW training aircraft used but no dedicated EW Canberra deployed.

An AEW/AWACs conversion of the SARO Princess was proposed ca. 1956.

[martinbayer]

While question 2) has already been addressed repeatedly, I'd just like to add that in addition to 'jet' airplanes that are powered by turbojets or turbofans there are also propeller airplanes driven by turboprop engines, all of which belong in the gas turbine family, so yes, it's been done.

As for the statement in question 5) that the "mission to Mars is still going ahead", I can only assume that you are referring to the Mars One concept, which currently mainly appears to consist of marketing efforts, as opposed to any of the actually ongoing Mars missions, such as the ISRO Mars Orbiter Mission Mangalyaan or the NASA Mars Atmosphere and Volatile EvolutioN Mission (MAVEN) Mars Orbiter. Pretty good summaries and assessments of the Mars One company as well as the overall project and its merits (or lack thereof) can be found at http://en.wikipedia.org/wiki/Mars_One and https://medium.com/matter/all-dressed-up-for-mars-and-nowhere-to-go-7e76df527ca0. As for whether they have "worked out how to get back to Earth", they haven't and they won't, since the mission architecture is explicitly and deliberately based on a one way trip to establish and grow a colony without a chance for a return ticket. But to paraphrase a more than two decades old statement of then Secretary of the US Air Force Sheila Widnall that she made with respect to space launch studies, "the Earth is covered by two thirds water and one third Mars mission studies", and the vast majority of crewed mission studies did indeed address the question of how to get back to Earth in more or less extensive detail. Fairly good introductory overviews over the various alternatives for getting humans to Mars and back can be found at http://history.nasa.gov/monograph21.pdf, http://webserver.dmt.upm.es/zope/DMT/docencia/motores-cohete/informacion-complementaria/Viaje%20a%20Marte.pdf, and https://engineering.purdue.edu/AAE/Research/Groups/longuski/Software/NOMAD/Papers/ComparativeAssessment.pdf, while NASA's most recent Mars Design Reference Architecture is documented at http://www.nasa.gov/pdf/373665main_NASA-SP-2009-566.pdf, http://www.nasa.gov/pdf/373667main_NASA-SP-2009-566-ADD.pdf, http://www.nasa.gov/sites/default/files/files/NASA-SP-2009-566-ADD2.pdf, and http://www.nasa.gov/pdf/373669main_2008-12-04_Mars_DRA5_Executive_Summary-Presentation.pdf, whereas ESA's corresponding effort is described in http://emits.sso.esa.int/emits-doc/1-5200-RD20-HMM_Technical_Report_Final_Version.pdf, so the question how to get to Mars from Earth and back again has already been answered repeatedly.

Hope this helps,

Martin

[kitnut617]

2)  could that be a ""natural"" gas turbine you're asking about, there are hundreds of those operating around the world, albeit they're usually mounted in front of a huge electric generator and fixed to the ground ---- they're called co-generation plants (I did quite a few drawings of the huge heat exchangers that the exhaust runs through some years ago)
3)  there was this one which was unusual  http://en.wikipedia.org/wiki/VFW-Fokker_614