Forum: X-planes

The J-58 was NOT a ramjet at all. It had ramjet-like qualities, because of the six bypass tubes that would take air from P4 and reroute straight to the afterburner. When at speed, the regular part of the engine still operated as a normal turbojet. The main thrust however, came from the inlets and its differential pressure.

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I'd have to ask two questions:

1) Why have a turbojet when you could have a turbofan?

Turbofans are much more efficient, both with fuel flow and operating temps

2) Do we need to go Mach 3?

I'd have to say no. Speed may be life, but L-O technology puts the crew at even less risk. Let me put it this way: Why dash away from a hostile threat at Ludicrous Speed, when you can ingress and egress the threat area without the threat knowing you were there?

The Concorde and Tu-144 proved what an inefficient waste SSTs were, and we also were able to trade the BONE's Mach 2 speed for lower RCS capabilities, while still retaining the ability to achieve Mach 1. No BONEs lost as of this writing, due to hostile fire, so I'd say that Rockwell got it right.

Someone who knows more about the GE engines can correct me but I think the B-70 was first designed with a boron burning version of the J93 in mind. Something like the J93-GE-5. That engine was to be rated at 33,000 pounds of thrust. They ended up using a more conventional non-zip fuel like JP-6 in the J93-GE-3 version of the engine and got about 30,000 pounds of thrust.

While the B-70 could hit Mach 3 for periods at a time I can't remember if it ever went one full hour at that speed, so I am not sure that it really could cruise at Mach 3 like the SR-71 did.

I can still remember as a little kid seeing air vehicle #2 being flown in on its last flight to Wright-Patterson for the museum.

TC wrote:

No BONEs lost as of this writing, due to hostile fire, so I'd say that Rockwell got it right.

Well, that's assuming they can even get a sortie off. They didn't get it that right Wink

Habu wrote:

Well, that's assuming they can even get a sortie off.

Yes, but when they FINALLY do... Laughing

...and they have a much better mission capable rate than the Blackjack. But I think we beat this horse to death in another thread. Wink

Yeah, I know, I just couldn't resist. Very Happy

But anyway, yeah I'm with ya, L-O is the way to go. I think it's been proven that higher-faster-farther doesn't work anymore.

You got it. Thumb

The B-70 was a very over-ambitious project, especially when considering the, at-the-time, future world events involving the U.S. Would the B-70 have been a viable weapon system in Vietnam? No way, and most especially not after the bombing halt up North.

The BUFF was easily converted from a nuclear strike platform to a conventional role. It would not have been anywhere near that easy with the Valkyrie.

Even if the AF had attempted to utilize the Valkyrie in a conventional manner, they'd have to slow down to an appropriate attack speed, which would have left them vulnerable to SAMs, and possibly high altitude airburst AAA.

Too fast, like its Mach 3 cruise speed, and they'd have run the risk of flying into China before being able to turn around.

I think cancelling the Valkyrie was one decision that McNamara got right. It was wrong for its time, and its cancellation eventually led to the BONE, which is a much more practical weapon system.

Occamsrasr wrote:

While the B-70 could hit Mach 3 for periods at a time I can't remember if it ever went one full hour at that speed, so I am not sure that it really could cruise at Mach 3 like the SR-71 did.

Kind of a silly reason. It flew at Mach 3 for 32 minutes. That was the amount of time required for a full heat soak and everything was fine so they ended the flight.

sferrin wrote:

Occamsrasr wrote:

While the B-70 could hit Mach 3 for periods at a time I can't remember if it ever went one full hour at that speed, so I am not sure that it really could cruise at Mach 3 like the SR-71 did.

Kind of a silly reason. It flew at Mach 3 for 32 minutes. That was the amount of time required for a full heat soak and everything was fine so they ended the flight.

I thought I remember it being longer than that, sure that wasn't just the first cruise test?

Prinz_Eugn wrote:

sferrin wrote:

Occamsrasr wrote:

While the B-70 could hit Mach 3 for periods at a time I can't remember if it ever went one full hour at that speed, so I am not sure that it really could cruise at Mach 3 like the SR-71 did.

Kind of a silly reason. It flew at Mach 3 for 32 minutes. That was the amount of time required for a full heat soak and everything was fine so they ended the flight.

I thought I remember it being longer than that, sure that wasn't just the first cruise test?

Several flights flew supersonic for an hour or two but the longest Mach 3 stretch was 32 minutes. Jenkins' Valkyrie book breaks down each flight of both XB-70s. One 2+ hr flight included testing engine air starts- at Mach 2.4. Shocked

TC wrote:

...and they have a much better mission capable rate than the Blackjack. But I think we beat this horse to death in another thread. Wink

Cheers TC! Very Happy

John.

This Bud's For You John Boy! Beer

Yeah, the B-70 was no doubt a good looking jet. Definitely in the top 4 for American strategic bombers as far as looks go. In no particular order, I'd say the dark gray BONEs, the Valkyrie, the Hustler, and the B-47...or maybe EXACTLY in that order.

However, looks don't hack it, compared to practicality...and as I said, Vietnam would have rendered the Valkyrie virtually useless. It wasn't made for that type of war, and had we purchased enough Valkyries to equip just a couple of Bomb Wings, people would have questioned their cost, need, and usefulness, when they would have sat out of the war for just that reason.

Hmmm...sounds a helluva lot like another bomber that I'm a big fan of. Wink

Salute!

Habu KNOWS about the Oxcart. So does Parrot-breath.

TEG (that engine guy) REALLY KNOWS!!!!!

We've gone thru this before and even posted the tech manuals and diagrams for the J-58. It had bypass ducts because it didn't need or could not use all that air at high mach numbers.

The neatest thing about the B-70 was the "shock rider" concept. I truly believe it would have done just fine in production, but requirements changed and we had a new administration and ........

Gums sends ...

I'm not up on the tech stuff, but I lived through the era.

There was a lot of pressure from the airlines to get the gov't to develop a supersonic aircraft. Everybody thought that the quick transatlantic flights would be a money machine. But, they wanted the government to fund the research.

Also, I think that there was the usual intenational competition for bragging rights.

The French won that one, but of course, it didn't matter in the end. Probably restricting US landing sites to avoid sonic booms didn't help ( I know that this happened early on, and I never heard that the restriction was removed)

TC wrote:

Vietnam would have rendered the Valkyrie virtually useless.

How so? Did it render ICBMs useless? We'd have still had the B-52s around to drop conventional bombs (don't know how accurate they could be dropped dumb from mach 3 and 80,000 feet though). And if the B-70s had managed to last to today (not impossible as we'd have babied those suckers) they'd be just the ticket for dropping deep penetration weapons.

Forum: X-planes

XB-70 Valkyrie