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RE: [PSUBS-MAILIST] Stopping Flaps, deep flight - Snoopy collision
I thought I'd elaborate on that collision scene, because there's obvious
lessons in it.
The camera was low in the cabin looking through the forward viewport,
but I was looking through the hatch dome. Unfortunately that means the
camera had an much better view than I did. I couldn't see the cable even
after hitting it, when I half got on the floor to look through the lower
viewport. The reaction time available to the pilot was zero, even though
visibility was considerably better than zero.
When that video was shot, I was using the two side thrusters for forward
propulsion. They have on/off switches and no speed control, so I use
them in bursts. But you just go too fast. I've since changed to using my
stern thruster for forward motion. Snoopy has a tiny stern thruster, and
unlike the side thrusters its wired with speed control. So now I can go
slowly. If I happened across that cable today I would still crash into
it, just more gently.
The other thing I've changed is buoyancy control. In the video I flooded
VBT until negative and then blew VBT until neutral after landing on the
bottom. That made for a nice descent shot, but isn't the way I'd
normally do things. I flood VBT until the apex of the dome is level with
the surface, and from then on unless there's a change in crew it's just
up and down all day using rotated side thrusters. In the sub I'm
building I'm planning on using only soft VBT, because there really isn't
any need to blow VBT at depth when you drive up and down on thrusters. I
suppose one may need to flood a tiny bit more if you hit a thermocline
on the way down. But the new sub also has a fixed vertical thruster with
speed control, which will make things even easier than in Snoopy.
Cheers,
Alec
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From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of
jonw@psubs.org
Sent: Wednesday, August 27, 2008 18:25
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] Stopping Flaps, deep flight
Hi Andy,
I attended UI, but missed Hawkes. I was only there for the one day that
I was speaking and I think Hawkes spoke the day before. Dan Lance was
there for Hawkes presentation though and could probably comment on it.
Dean, check out Alec Smyth's video from the 2006 convention when
"Snoopy"
ran into an underwater cable that was suspended about a foot or so off
the bottom. The cable is first visible at about time mark 2:23, and
collision occurs at about time mark 2:25. Assuming Alec had a speed
brake of the kinds that have been discussed, he would have had about two
seconds to react, throw the switch on the brake, and then have the brake
deploy and actually start working. In the film, it appears obvious that
Alec never saw the obstruction and therefore couldn't have reacted to it
to deploy a brake.
You'll notice that the motors on "Snoopy" are still running even after
first contact with the cable. With the force of the motors continuing
to push "Snoopy" against the cable, it "snaps" upward which makes a loud
noise and gets Alec's attention. Then you hear him stop the motors and
the tension in the cable pushes the sub backwards. I'm not very good at
guessing speed through water, but I suspect he was doing no more than 3
knots. Even in clear deep water, visibility may be limited to the
distance your lights are thrown.
Jon
-----Original Message-----
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org]On Behalf Of Andrew
Goldstein
Sent: Wednesday, August 27, 2008 4:56 PM
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] Stopping Flaps, deep flight
Jay,
Agree with the points in last email, still seems somewhat within the
realm of possibility to do it. But might be silly to discuss it
further, at least without putting some numbers on everything. Esp.
without a reason to be going fast near obstructions and or wanting to
stop really fast.
In regards to Deep Flight. Graham Hawkes gave a talk at last UI about
progress he was making. I wasn't there, but I think maybe jon was?
Anyway, I probably don't have any more info than you do. I know the
first Deep Flight I was successful enough to help secure funding for
further subs. The also did (do?) have a "flight school" for the deep
flight aviator which probably brought in some cash. He has sold the new
one "super falcon" for $2,000,000. I suppose it depends how you measure
success. There were certainly more k-250 hulls built so if # of hulls
is the metric than....But I guess I would say if the sub comes back up
and helps the builder go on to build more subs that it was a success.
It is pretty cool no mater how you look at it. But very $$$$ which may
also limit the number of hulls and
cause the owner to be very very careful with it. Also, I think more
often
than not most uses of subs preclude fast hydrobatic type vehicles (like
making movies or doing science
etc.) so something like Deep Worker, JSL, or a k-250 will get more
operational time.
He did get a cameo on the opening theme to that last short-lived star
trek tv show...:)
-a
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