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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