Hi Charlie,
For the solenoid valve selection, just make sure all the wetted parts of
the valve are compatible with your propellants. You'll have to dig in the
spec sheet of the valve you're looking at, and figure what the material is
used for each parts that will get in contact with the propellant, then do a
Google search on the compatibility, for example: "EPDM GOx compatibility"
to get started. Over time you'll find some really useful references that
you'll want to bookmark because you'll end up doing this type of research
very often.
If the valves are inexpensive, you could do some quick compatibility tests
with it. For example, have some IPA sit in the valve for a week, then check
if the valve is working properly. If a specific components are specially
concerning (for example you can't find information on its compatibility or
you're finding conflicting information from different sources), maybe take
the valve apart and let the component bath in IPA for days/weeks and look
for swelling, discoloring, softening, etc.
You have to be fairly prudent with GOx as it will react with a lot of
material so make sure to use Oxygen compatible materials. Moreover, you'll
need to have parts kept really clean since GOx could ignite with something
as simple grease from your hand. I recommend looking up "oxygen
cleanliness" or "oxygen service" for more info on this.
Also if you're going to use check valves as pressure relief devices in your
lines, makes sure their cracking pressure is high enough to not open under
nominal conditions. Pressure relief valve is normally used for this
application.
Fittings are fine so long as they are properly installed and compatible
with your propellant. You'll probably want to "leak check" your lines
before putting any propellant in. A good first step is to pressurize your
lines with nitrogen at low pressure at first and spray soapy water around
each of the threads. If there is a leak, you'll see bubbles forming.
Whenever using nitrogen, be sure to be a well ventilated area as Nitrogen
can displaced breathable air if you're in a small space and make you pass
out.
Fittings are a whole topic of their own and it can be quite overwhelming at
first. Probably the most easily available fittings around you will have NPT
threads so maybe build your system around that. It's not the best but
should get you started. You will need some PTFE thread seal tape. Again,
use Oxygen service PTFE tape for your GOx side as well.
Sorry for the brain-dump but hopefully this helps. As you can see, there is
a lot of things to take into account but a way to deal with the complexity
is to split your system into smaller simpler sub-systems and make each work
independently before moving on to the next one. At the end, you put all the
working solutions together and hopefully it all work together as well.
And don't hesitate to test, test and test! You willl have a lot questions
as you build your rocket on what will work or not. Most often the only or
best way to find out is to test it.
Good luck and keep it fun always!
Miguel
On Wed, Feb 3, 2021, 12:19 PM Charlie Jackson <charliejackson8629@xxxxxxxxx>
wrote:
Hi everyone,
I’m looking into various parts for the plumbing side of my engine (valves,
pipes, regulators etc) and I have a few questions.
1)Can generic, fairly inexpensive solenoid valves be used for
fuel(isopropyl alcohol) and Gox lines on the inlets? I’m not concerned
about high pressure as all lines will have a safety check valve downstream.
For fuel tanks I certainly will have high pressure valves.
2)I intend to implement a microcontroller for autonomous abort options,
any tips on ways to actively read combustion chamber properties like
temperature and pressure electrically with a sensor and how would I prevent
it from getting damaged?
3)Some parts of the plumbing will be quite awkward to bend into various
directions so I’ll have to use fittings, is this prone to leakage? I’m
using nitrogen, gaseous oxygen, and alcohol. And if so, how should I
mitigate the leakage?.
4)How do you suggest I implement ignition sources into my design? I’m
looking for engine re-start capability so things like electrical matches do
not suffice
Apologies for the non-stop questions I ask on here. I’m fairly young (14
years old) and I love learning about rocket propulsion so I can’t
articulate how thankful I am to all of you.
From Charlie.