Radios are a possibility but I would not use common frequencies.
I would want some type of handshake (modem) for security.
-------- Original Message --------
Subject: [AR] Re: Safing of liquid vehicle
From: qbert@xxxxxxxxxxxxxxx
Date: Tue, November 10, 2015 10:42 pm
To: arocket@xxxxxxxxxxxxx
433 and 900mhz radio modems are a dime a dozen
and a very easy way to control just about
anything via your servo actuated ball valve or
even simpler, a 2.4ghz RC radio and receiver tied
into your abort system. Run them on a completely
separate circuit with their own power source and your golden.
Robert
At 06:13 PM 11/10/2015, you wrote:
Here's a less destructive idea for venting the
fuel tank - if it's still on the pad, pop the
burst disc with a pellet gun from 50 feet away
or so. The tank will be full and incompressible
so it shouldn't be too much energy
release. Might be tough to hit that small of a
target though (1/2 inch). Maybe an external
mechanism to pop the disc would work but it
would have to not interfere with the fins. Could
one of the super duper high power lasers burn a
hole in it? Probably not since it's an aluminum disc in an aluminum holder.
If power is still available but just no comms,
LEDs across the ball valves can indicate
solenoid states. Microswitches might work to control LEDs for the ball
valves.
-Bob
On Nov 10, 2015, at 19:01, Robert Watzlavick
<<mailto:rocket@xxxxxxxxxxxxxx>rocket@xxxxxxxxxxxxxx> wrote:
If I lose comms after closing the vents but
before launch, the LOX tank will self vent at
abt 750 psi through a burst disc. That should
bleed down most of the helium through the LOX
regulator and the now open burst disc outlet.
The pressurized fuel tank is a little more
difficult as it will require a manual drain. If
it's still intact on the pad, no big deal. The
tank I'm using has about 2.5x factor of
safety. If it's crashed somewhere or blown up
on the pad, I'm not so interested in walking up
to it and the rifle may be a better
solution. However once the engine starts, I
plan to never close the main valve so everything should eventually bleed
down.
If I lose comms after a valve command, I see
where you're going, hmmm, for a skinned vehicle
where everything is internal, it would be hard
to tell the position of a ball valve
externally. The valve outlets are flush with
the skin so you can always look at the ball to
see if it's open our closed but that would
require putting your eyeball up to the
vehicle. Maybe some sort of flag attached to
the valve shaft but you'd have to have a window or viewing port to see it.
- Bob
On Nov 10, 2015, at 18:37, Paul Breed
<<mailto:paul@xxxxxxxxxx>paul@xxxxxxxxxx> wrote:
The real issue is what do you do when you've
lost communication with the vehicle and its in unknown state.
Some external visual clues as to its current state would be very useful.
With blue and silver the main vent valve would visually pop open....
A good scoped rifle is a remote depress of last resort...
From 50 yards you should be able to reliably depress in a 2" circle.
For a liquid rocket I would retain such
capability and ensure that I'm clear down range...
Nothing worse than sitting in the bunker
waiting for the lox tank to go boom with no way to change the outcome....
I watched one group go out to a
crashed burned pressurized lox rocket and
manually open a vent valve.... this was a
vehicle that used cheap fire extinguisher
tanks... so the cost to ventilate the tank was
low. I offered them other tools... alas hoplophobia wins out over common
sense.
Paul
On Tue, Nov 10, 2015 at 3:23 PM, Robert
Watzlavick <<mailto:rocket@xxxxxxxxxxxxxx>rocket@xxxxxxxxxxxxxx> wrote:
The opto controlled relays provide that
capability. To enable power, the switch
providing power to the opto LED high side has
to be on (either a switch or shorting plug)
and then a bit from the onboard computer has
to be set appropriately for the LED low side.
For the smart servos, you also have to send a
command to get them to move (they power up in
standby). The only potential issue is that
you're assuming the MOSFET on the output side
of the relay won't get turned on by itself.
Seems really unlikely to me but still a potential failure mode.
I was considering the Molex Mini-Fit Jr series
of connectors (same series as ATX power
supplies) for power. They have a latch for
internal onboard use (vibration resistant)?and
I can break off the latch for the ground
supply connector so it pulls away on liftoff.
-Bob
On Nov 10, 2015, at 16:35, Pierce Nichols
<<mailto:piercenichols@xxxxxxxxx>piercenichols@xxxxxxxxx> wrote:
I agree that any rocket should be able to sit
on the pad under ground power all day long.
If its power draw is low, you could use a
1/4" phono plug -- they're cheap, low
profile, have some spring retention for wind
etc while still being easy to pull straight
out, and they can handle a few amps.
It seems like we need parallel safing systems
-- a 'soft' system that can be engaged and
disengaged remotely and a 'hard' system that
requires some sort of physical intervention
(pins, plugs, etc). So, in the re-safing
scenario, the operator engages the soft
system and then someone runs up to the rocket
quickly and engages the hard system.
-p
On Tue, Nov 10, 2015 at 1:46 PM, Paul Mueller
<<mailto:paul.mueller.iii@xxxxxxxxx>paul.mueller.iii@xxxxxxxxx> wrote:
Seems that a safe/arm system may have to be
at least partially dependent on onboard
power, and then the question becomes how do
you make onboard power as reliable as
possible for various failure scenarios? One
way would be a ground-based charging
connection much like a laptop (runs on ground
power and keeps onboard batteries charged
until you disconnect it). That way you could
sit on the pad, powered up, all day long if
you need to, as long as you have gas for your
ground generator! You could have a magnetic
connection like an Apple laptop, which could
be fairly easily reconnected if needed with a
rotating arm. Then do your arming/safing
remotely via something like a TV remote
control or even a laser pointer aimed at a
photoreceptor on the side of the rocket. It
would also be smart to have LEDs indicating
the arm status of your various systems (visible through binoculars).
On Tue, Nov 10, 2015 at 2:33 PM, Paul Mueller
<<mailto:paul.mueller.iii@xxxxxxxxx>paul.mueller.iii@xxxxxxxxx> wrote:
The re-safing problem seems to be the most
difficult, as the concepts so far seem to
involve pulling a pin or a rare earth magnet
with a long string. It's hard to "push on a
rope" to reinstall a pin, etc. from a
distance if necessary. I'm at a loss to
figure out a contraption that would allow you
to remotely arm and safe the rocket
mechanically. Maybe a rail-mounted rotating
arm that would return to the same spot
(assuming the rocket didn't move during a launch attempt, misfire,
etc.)...?
On Tue, Nov 10, 2015 at 10:59 AM, Pierce
Nichols <<mailto:piercenichols@xxxxxxxxx>piercenichols@xxxxxxxxx> wrote:
Here's a (half-baked) thought:
Make the shorting switches mosfets instead of
physical switches and drive the mosfet gates
either with a single shorting plug or with a
hall effect switch. The cool thing about the
hall effect switch is that you can place it
in the skin of the rocket with a small piece
of steel. Then your shorting plug become a
rare earth magnet stuck to the outside of the
rocket... which can be easily pulled off with
a long cord when it comes time to arm the
rocket. On the flip side, as long as there's
nothing else ferromagnetic near it, you can
re-safe the rocket by tossing a small magnet at it.
-p
On Tue, Nov 10, 2015 at 9:24 AM, Robert
Watzlavick <<mailto:rocket@xxxxxxxxxxxxxx>rocket@xxxxxxxxxxxxxx> wrote:
I have 5 opto relays I need to disable so I
would need multiple contacts - GOX igniter
solenoid, fuel igniter solenoid, CDI module,
servo power, and recovery motor power. I
could do a multi-pin connector and shorting
plug or go with a switch that grounds the + lead for all the optos.
-Bob
On Nov 10, 2015, at 10:11, Paul Breed
<<mailto:paul@xxxxxxxxxx>paul@xxxxxxxxxx> wrote:
The Short across the opto with an external
plug does not have to be to ground, just
short across the opto input pins. The 820
ohm resistor will be more than enough to isolate the cpu from damage....
On Tue, Nov 10, 2015 at 7:04 AM, John Dom
<<mailto:johndom@xxxxxxxxx>johndom@xxxxxxxxx> wrote:
Actually, âFailure is not an optionâ is
a Gene Kranz book. Not C. Kraft.
jd
From:
<mailto:arocket-bounce@xxxxxxxxxxxxx>arocket-bounce@xxxxxxxxxxxxx
[mailto:arocket-bounce@xxxxxxxxxxxxx] On Behalf Of Nels Anderson
Sent: dinsdag 10 november 2015 13:48
To: <mailto:arocket@xxxxxxxxxxxxx>arocket@xxxxxxxxxxxxx
Subject: [AR] Re: Safing of liquid vehicle
Something similar was considered, though not
actually done, when NASA's first attempt
launch a Mercury capsule resulted in a
four-inch flight in November 1961. From
Wikipedia
(<http://en.wikipedia.org/wiki/Mercury-Redstone_1>en.wikipedia.org/wiki/Mercury-Redstone_1):
"[T]he fully fueled and powered-up Redstone
was now sitting on LC-5 with nothing
securing it to the pad. Various other
dangers existed as well such as the
capsule's retrorocket package and the
<https://en.wikipedia.org/wiki/Range_safety>r
ange safety destruct charges. Furthermore,
the capsule's main and reserve parachutes
were hanging down the side of the rocket,
threatening to tip it over if they caught
enough wind. Fortunately, the weather
conditions were favorable. Amid the panicked
atmosphere in the control room, the launch
team was unable to come up with quick and
viable options to rectify the situation.
Chris Kraft, the now-frustrated flight
director, rejected several unsafe
interventions, including getting a rifle and
shooting holes in the booster's propellant
tanks to depressurize them. He eventually
took the advice of one of the test engineers
to simply wait out the battery discharge and let the oxidizer boil off."
Wikipedia cite's Kraft's biography, _Failure
is not an Option_, as its source.
On 11/09/2015 02:58 PM, Ben Brockert wrote:
Only an 'unreasonable' person would
carefully shoot off a vent cap with a .30-06
when the servo-actuated normally closed vent
on their spherical peroxide rocket doesn't actuate.
On Monday, November 9, 2015, Robert
Watzlavick <<mailto:rocket@xxxxxxxxxxxxxx>rocket@xxxxxxxxxxxxxx> wrote:
I've heard similar anecdotes - has this technique ever actually been
used?
-Bob
On 11/09/2015 01:40 AM, Michael Clive wrote:
.3006 will safe it pretty good and solid.
--
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