Basic Turboprop vs turbofan Q

[megan]

Having said that, the B52 still uses turbojets for some reason

Nope, turbofans.

What analysis do you have that the Bear is is inefficient fuel wise? Doubt it very much.

[tdracer]

Early B-52s used turbojets, but the G and H models (which are all that are left in service) use low bypass turbofans. There have been a number of studies to re-engine the B-52 with more modern high-bypass turbofans (I was involved in a couple studies in the late 1990s using either the PW2000 or RB211-535 from the 757). The improvements in performance and fuel burn were astounding, but the program never go the go-ahead. One rumor was that the USAF brass were against a B-52 re-engine since it would make it harder to justify a large B-2 buy (which they ultimately didn't get either ).


BTW, the Bear may be able to top out at .87 Mach, it's cruise speed is less than .7 Mach, and it's burning plenty of fuel when it tops out at 0.87. The Bear's counter-rotating props mimic one of the other advantages I noted about turbofans - fan exit guide vanes - but at the penalty of huge noise.

[megan]

tdracer, the B-52 re-engine program is again under review, only the H remains in service, the G was J57 powered and the last aircraft was retired under the New START treaty requirements in December 2013.

B-52 Re-engine Resurfaces As USAF Reviews Studies | Defense content from Aviation Week

[Chu Chu]

Interesting that they're looking at 8 turbofans.

[deptrai]

when the Tu 95 was developed many decades ago Turbofan technology was relatively new and not fuel efficient enough for the required endurance. Since then, turbofan technology has matured. A bit off topic, one Tu 95 had a nuclear reactor on board, as a test bed, a first step to experiment with nuclear powered aircraft. The reactor didnt power anything, they were just experimenting how to build a reactor into an a/c (and how to shield crew etc). Luckily, intercontinental missile technology made the experiments towards nuclear powered bombers obsolete. Sorry for the thread drift...but I'm very happy people are discussing turbofan vs turboprob here today...and not nuclear powered a/c

[Skornogr4phy]

My mistake. I forgot about the low bypass turbofans.

[A Squared]

Originally Posted by deptrai

A bit off topic, one Tu 95 had a nuclear reactor on board, as a test bed, a first step to experiment with nuclear powered aircraft. The reactor didnt power anything, they were just experimenting how to build a reactor into an a/c (and how to shield crew etc).

The US did approximately the same thing with a B-36