Small externally visible pressure gages would work...
Something like..
http://www.mcmaster.com/#atmospheric-pressure-gauges/=zr9l0h
What you really want to know is still presurized or not...
On Tue, Nov 10, 2015 at 5:13 PM, Robert Watzlavick <rocket@xxxxxxxxxxxxxx>
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 <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 <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 <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 <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 <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 <
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 <
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 <
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 <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 <johndom@xxxxxxxxx> wrote:
Actually, “Failure is not an option” is a Gene Kranz book. Not C.
Kraft.
jd
*From:* arocket-bounce@xxxxxxxxxxxxx [mailto:
arocket-bounce@xxxxxxxxxxxxx] *On Behalf Of *Nels Anderson
*Sent:* dinsdag 10 november 2015 13:48
*To:* 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 (
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 range safety
<https://en.wikipedia.org/wiki/Range_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 <
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.
--
____________________________________________________
