Blue Streak

Neil Gerace wrote:


Since the Blue Streak was designed in the Northern Hemisphere but tested in
the Southern, the design and actual vortices would cancel each other out and
none would form.



Should have saw that one coming a mile off... :-)
The real problem with the missile though was that, like an egg, it could
only be elevated into the vertical position on the spring and fall
equinoxes- a severe operational constraint. The United States and
Soviet Union got around this problem by putting theirs in silos. Since
the sun didn't shine on them, they were unaffected by its influence;
but they were still liable to misbehave at the time of full moons, due
to tidal effects on their gyroscopes- causing them to behave in an
erratic manner.

Pat

"Pat Flannery" wrote in message
...

Here's why: if you look at the photo of the vehicle, you'll note that the
missile's body with the exception of the LOX area uses _external ribs_ for
strengthening.

Doesn't the Saturn S-IC stage have external ribs as well? I don't have any
photos handy though.

In article . com,
wrote:
They were there mainly as belts and braces to stiffen the structure.
The idea was that if for any reason the kerosene tank had to be drained
with the LOX still in place, then the missile would still be
structurally safe [the missile was intended to be silo based].

Of course, you can do that even with a balloon tank -- you just have to
keep the tank pressurized throughout. The liquid in the lower tank
doesn't play any part in supporting the upper tank. Admittedly, a
requirement for continuous pressurization that makes draining the lower
tank a bit more complicated, but it is feasible.

In practice they did seem to be redundant, but as far as I know, no one
ever bothered to do any subsequent investigation as to whether they
were still necessary.

Such reviews of early design decisions often don't get done until the
design is explicitly revised for some reason. It's easier to leave things
as they are unless there's specific reason to change.

Only Blue Streak and Atlas ever used the stainless steel balloon
concept. Structurally, they were both very efficient. Ayone any idea
why it was never used again [except that von Braun didn't like it]?

There was one more user: the Centaur upper stage. It's now the only one
left; the very last balloon-tank Atlas flew a few days ago.

Balloon tanks were always fighting an uphill battle for acceptance; it was
considered a weird and somewhat untrustworthy approach. The Titan ICBM
was started as an Atlas backup partly because a fair number of people
expected Atlas's balloon tanks to be a disastrous failure. One of the
ground rules for the shuttle design was "no balloon tanks".

(MSFC was greatly displeased to discover, late in shuttle development,
that a small design oversight in the ET required that the LOX tank be
pressurized during filling. It was self-supporting empty or full, but at
one intermediate level during filling, there was some chance of buckling
under thermal-contraction stress without internal pressure.)

There's no denying that it *does* complicate manufacturing and ground
handling a bit. A few Atlases and Centaurs were written off or needed
major repairs because of loss-of-pressure accidents.

I think the biggest reason why they never got more use, apart from sheer
institutional prejudice, was that designers never again felt quite that
pressed to get maximum performance from a single stage. Much of the
incentive to accept inconveniences for the sake of performance went away
when staging -- more specifically, engine ignition at high altitude --
became routine practice.

The technology of lightweight structures also advanced considerably,
making balloon tanks less necessary. Titan II and the shuttle ET have
quite remarkable mass ratios with non-balloon structures.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |

"Pat Flannery" wrote in message
...

Should have saw that one coming a mile off... :-)
The real problem with the missile though was that, like an egg, it could
only be elevated into the vertical position on the spring and fall
equinoxes- a severe operational constraint. The United States and Soviet
Union got around this problem by putting theirs in silos. Since the sun
didn't shine on them, they were unaffected by its influence; but they
were still liable to misbehave at the time of full moons, due to tidal
effects on their gyroscopes- causing them to behave in an erratic manner.

Being British, the sun shone out of its .. er .. Rolls-Royce end, so that
was no problem either

In article ,
Neil Gerace wrote:
missile's body with the exception of the LOX area uses _external ribs_ for
strengthening.

Doesn't the Saturn S-IC stage have external ribs as well? I don't have any
photos handy though.

External stiffeners are not uncommon. The S-IC tanks weren't stiffened,
but the non-tank parts of the stage -- the lower skirt, the intertank
ring, and the upper skirt -- were. (And just to add insult to injury,
I'm told that the three different stiffened sections had three different
stiffener counts, making life difficult for the guys running wiring
tunnels etc. up the exterior.)

The shuttle ET's intertank ring has external stiffeners.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |

Henry Spencer wrote:

However, I would think that said conductive cooling is likely to be pretty
effective, with a cryogenic fluid just the other side of the skin...

But this is going to occur in a very short period of time, virtually
instantaneously as the LOX hits the wall of the tanks- the ribs are
going to take several seconds to cool down via conduction, varying by
what they are made out of, and its conductivity.
Did this missile start out being intended for kerosene/hydrogen peroxide
propulsion by any chance? Because the balloon tank looks like something
that got changed from the original design.



Have there been cases of "bathtub drain" vortices forming in rocket
propellant tanks during flight?



Yes, and it's fairly routine to put a vortex baffle at the tank outlet.


I've seen those in cutaways.

Pat

wrote:


They were there mainly as belts and braces to stiffen the structure.
The idea was that if for any reason the kerosene tank had to be drained
with the LOX still in place, then the missile would still be
structurally safe


Now that's a weird scenario; was that in case they had an aborted
launch, and wanted to safe the missile before ground crew were let near it?

In practice they did seem to be redundant, but as far as I know, no one
ever bothered to do any subsequent investigation as to whether they
were still necessary.

There were 48 of them: what that came to in terms of weight I have no
idea.

Only Blue Streak and Atlas ever used the stainless steel balloon
concept. Structurally, they were both very efficient. Ayone any idea
why it was never used again [except that von Braun didn't like it]?



Having to keep the rocket pressurized with gas at all times was a pain
in the rear- any leak when it was in the vertical position and it would
crumple up under its own weight (like happened to the Centaur stage a
few years back when it was accidentally punctured while on the pad). I
imagine that there were problems that arose in transporting it in this
condition also; varying height above sea level and air temperature
changes would change the pressure in the tank. You'd need a emergency
overpressure relief valve, and a way of topping up the tank's pressure
if it fell too low.

Pat

wrote:

The major difference
was that the Blue Streak design was a U tube; Titan II a Y shape.



Actually it was a "W" shape, with the missile over the center point of
the "W". The exhaust came up a duct on either side of the silo.

Pat

In article ,
Pat Flannery wrote:
Did this missile start out being intended for kerosene/hydrogen peroxide
propulsion by any chance? Because the balloon tank looks like something
that got changed from the original design.

Although there was considerable interest in peroxide, there seems to have
been a decision quite early that funding simply would not permit building
up British large-engine expertise quickly enough for Blue Streak. That
meant licensing US engine technology, and that implied LOX/kerosene. So
I don't think it likely that there was a mid-stream propellant change.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |

Neil Gerace wrote:

Doesn't the Saturn S-IC stage have external ribs as well? I don't have any
photos handy though.


Both intertank and interstage areas on the Saturn V used ribbed
construction for strength*; which got me thinking about the temperature
contraction aspect, as the external walls of the propellant tanks don't
use external ribs. The obvious reason for choosing ribs is that they add
strength at low weight in the sections where they are used; so there
must be some reason that you don't use them over the whole vehicle, and
temperature contraction effects would be an reasonable explanation for that.

* From the bottom up: first stage- ribbed motor housing, smooth
kerosene tank, ribbed intertank structure, smooth LOX tank, ribbed top
interstage support. Ribbed interstage. Second stage- ribbed second stage
base structure, smooth LOX/LH2 tankage, ribbed top interstage support
structure. Ribbed interstage. Third stage- ribbed third stage base
structure, smooth LOX/LH2 tankage, ribbed spacecraft support structure.

Pat