Address

Author Topic: Rockets!  (Read 3740 times)

f00bard

  • FamiLAB Member
  • Newbie
  • *
  • Posts: 0
  • Da Real MVP
    • View Profile
Rockets!
« on: July 10, 2012, 11:13:30 PM »
Thomas McNeill is a member of the public that's visited us a few times.  He came to Micro Monday once to show off these PIC modules he makes, and also had a booth at Maker Faire.  The story with his PIC modules is that he designed them for a rocket he would like to build.

I know Hybridsix has always wanted to build a rocket, and I'm in the same camp.  I chatted with Darkmoonsinger this evening and she's attending a class on HPR in the near future.  Thomas has asked if we'd like to build a rocket motor and eventually a rocket.

Here's his recent email after a discussion we had at open house:

Quote
I put some numbers together.  We can make a 500lb thrust engine
rocket engine using Liquid Oxygen and Kerosene.  The shop lathe won't
be able to handle making a 250lb engine though.  The biggest the chuck
can grab is 2.5" OD.  I'd have to machine that stuff on my own.  Fami
could definately make the test stand and could do the plumbing and
testing.  The liquid oxygen would have to be stored in a dewar but the
kero could be purchased on the drive over before testing.  A helium
bottle would also need to be stored on site in a bottle.

Now I could put together a hybrid engine that could be built using the
tools you guys have.  Plastic and Nitrous Oxide so that would be cool
as well.

I'm thinking we'd start with the hybrid plastic/nitrous engine and work our way up to a liquid fuel rocket.  We'd need to build a testing frame to hold the motor.  Eventually we'd work on a rocket and avionics with eyes towards a real launch!

So I'm posting this preliminary info in hopes of gauging interest and getting people talking about this, and I'm hoping to get Thomas weighing in at some point.

Looking forward to your responses!

ThantiK

  • FamiLAB Member
  • Full Member
  • *
  • Posts: 237
  • Resident 3D printer guru.
    • View Profile
Re: Rockets!
« Reply #1 on: July 11, 2012, 03:46:40 PM »
The chuck on our lathe can grab stuff from an inner diameter too.  It's not just for clamping the outsides.  I'm majorly interested in this, but have literally 0 knowledge on the subject.

darkmoonsinger

  • Treasurer
  • Administrator
  • Hero Member
  • *****
  • Posts: 741
  • I am no one but all that I am.
    • View Profile
Re: Rockets!
« Reply #2 on: July 11, 2012, 06:28:04 PM »
We can all learn together.  :D

johnbentcope

  • FamiLAB Member
  • Hero Member
  • *
  • Posts: 584
  • I make technology into art and art into porridge.
    • View Profile
    • JohnBentCope
Re: Rockets!
« Reply #3 on: July 11, 2012, 06:41:43 PM »

Everyone learn together now!
I like colors.

willasaywhat

  • Administrator
  • Hero Member
  • *****
  • Posts: 987
    • View Profile
Re: Rockets!
« Reply #4 on: July 11, 2012, 11:52:07 PM »
Would be cool to do some "research" with hobby engines... Think we could get away with setting off a few in the field? ;)

electrimod

  • FamiLAB Member
  • Newbie
  • *
  • Posts: 19
    • View Profile
Re: Rockets!
« Reply #5 on: July 12, 2012, 10:25:38 PM »
Start Here:  NASA SP-125: "The Design of Liquid Propellant Rockets"  2. edition by Huzel and Huang 1971

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19710019929_1971019929.pdf[/url]

And a little more simple:
http://www.cientificosaficionados.com/libros/cohetes.pdf

Hybrids are a lot less documented though.  They do simplify some aspects with the trade off predictability.  You only have one fluid to work with in a hybird.  You can use Nitrous Oxide or Liquid Oxygen.  The N2O will be self pressurized.  That is nice but tanks/body are heavy due to it being very high pressure. See http://encyclopedia.airliquide.com/Encyclopedia.asp?GasID=55  In Florida our temperatures push the limits on it as well.  Tanks need blow off valves and burst disks for safety.  The density here in FL can be very low due to our higher temperature.  Some people keep their tanks in ice baths before filling to reduce pressure and increase density.

One problem with Nitrous Oxide is that when it breaks down it is exothermic, creates heat/energy, and if there is any excess friction in the lines or a hard water hammer effect from a valve the shock wave or heat can cause it to breakdown.  This then cascades and it goes boom.

Liquid Oxygen is very cold.  You have to work with cryo and rent a dewar.  Very cheap though.  Probably the best performance but you will need to pressurize it with Helium.  Nitrogen would be nice but it dissolves in LOX and will really mess up your run performance and stability.

Hybrid fuels can be anything.  Wood, Plastics, or Wax.  The main concern is regression rate.  The material has to burn away at a sufficient rate to yield fresh un burned fuel for the oxidizer to burn.  If this doesn't happen you can't get the performance you really want.  Nitrous benefits from this because it does good from 12:1 to 2:1 Oxidizer for Fuel ratio but LOX likes to be near 2:1.

Here is some videos of a bipropellant motor I helped build.  It ran on Nitrous and Propane.
http://www.exoge.com/mambo/content/view/26/46/
Electrimod.com - Modular Electronics
Exoge.com - Modular Simplicity

electrimod

  • FamiLAB Member
  • Newbie
  • *
  • Posts: 19
    • View Profile
Re: Rockets!
« Reply #6 on: July 17, 2012, 12:27:45 AM »
One big details that is really essential to an oxidizer choice is the density.  Nitrous has a great density of 1222kg/m3 (70lbs/ft3) at its melting point which is -88.5C.  At room temp the density is terrible.  It is under 50lbs/ft3.  That means you need way more tank to carry the oxidizer needed.  Most fuels are around 50lbs/ft3
Liquid Oxygen has a good density since it comes from the dewar cryogenic.  Nitrous oxide can be chilled to lower the density but then you lose the vapor pressure which is one of the reasons to use it so you have to pressurize it and then you might as well just use LOX.
 
 
 
Electrimod.com - Modular Electronics
Exoge.com - Modular Simplicity

f00bard

  • FamiLAB Member
  • Newbie
  • *
  • Posts: 0
  • Da Real MVP
    • View Profile
Re: Rockets!
« Reply #7 on: July 17, 2012, 01:02:19 PM »
And a little more simple:
http://www.cientificosaficionados.com/libros/cohetes.pdf

This PDF was very accessible.  Good stuff.

Also checked out this video on the latest rocket that the guys at Copenhagen Suborbital tested: http://www.youtube.com/watch?feature=player_embedded&v=bqASqda0ylc

I find it both amusing and awesome that the tech they're working with is basically 1950s era NASA tech.

electrimod

  • FamiLAB Member
  • Newbie
  • *
  • Posts: 19
    • View Profile
Re: Rockets!
« Reply #8 on: July 18, 2012, 12:22:06 PM »
In order for us to proceed we need to a few things and have a few decisions
I.  Build a Test Stand
     A.  Vertical
          1.  Pro: Vertical is good because engine fly in the same orientation and fuel or oxidizer can't pool in the engine
          2.  Con:  You don't want to burn holes in the ground so you need a deflector
               a.  Red fire bricks
               b.  Cement blocks
               c.  Both will be consumable.
          3.  Con:  Height is an issue because you don't want the flame and heat deflected back up toward the engine and electronics
          4.  Pro:  Anchoring only requires the stand to be weighted down
     B.  Horizontal
          1.  Con:  Fuel or oxidizer can pool in the engine if a valve doesn't fully close and lead to hard start/explosion
          2.  Con:  Stand needs to be anchored so that the thurst doesn't push the stand.
               a.  Could be bolted to the side of the loading dock
               b.  Anchored in to parking lot or dirt using hurricane anchors
          3.  Pro:   There will be plenty of room for the flame to extend fully without be disturbed
II.  Engine Type
     A.  Hybrid Engine
          1.  Pro:  Easy implentation
               a.  Less Plumbing
               b.  Less valves
               c.  One less transducer
               b.  One less propellant tank
          2.  Con:  Not easily characterized
               a.  Performance data requires multiple runs
               b.  regression rate requires multiple runs with multiple chamber lengths
                    regresssion is the rate the fuel burns.  It is based on melting point
                    and the surface area and many many factors.
          3.  Oxidizer
               a.  Nitrous
                    1.  Con:  Can be dangerous due to high pressure
                    2.  Con:  Florida's summers don't help keeping the pressure low due to heat
                    3.  Con:  The liquid is near or at it's critical point due to temperaure which means very poor density
                         a.  Bad for launching
                         b.  Flow can be two phase in plumbing and injector, liquid and gas, which makes for poor performance.
                    4.  Pro:  Self pressurized
                    5.  Pro:  Oxidizer to Fuel Ratio is anywhere from 12:1 to 2:1 which same performance
                         a.  Pro:  Most of the energy comes for the breaking of the N2O and not from the burning of the fuel
                         b.  Pro:  Less solid fuel required
                         c.  Pro:  Makes getting the fuel surface area numbers correct due to good performance over a wide O/F range       
               b.  Liquid Oxygen
                    1.  Con:  Cryogenic
                    2.  Con:  Dewar rental
                    3.  Con:  Requires narrow O/F range
                    4.  Pro:   Better overall performance
                    5.  Pro:   Better density which is good for flight
                    6.  Con:  Requires a pressurant system that uses Helium
     B.  Liquid Bipropellant
         1.  Pro:  Easier to calculate performace
             a.  Calculations much closer to actual real performance
             b.  O/F Mixture ratio's are easy to get right
         2.  Con:  Two tanks each with a pressurant unless Nitrous is the oxidizer
         3.  Oxidizer:  Same choices as the hybrid
         4.  Fuel Choice
             a.  Kerosene/Diesel
                 1.  Pro:  Good performance
                 2.  Con:  Spills harder to cleanup
                 3.  Con:  Leaves oily mess
                 4.  Con:  Not as green, Cartman hates hippies
                 5.  Pro:  Easy to get
             b.  Ethanol/Methanol/Isopropyl
                 1.  Pro:  Evaporates to leave no mess
                 2.  Pro:  Greener
                 3.  Pro:  You can run the engine on everclear or 151 for fun
                 4.  Con:  Lower performance
                 5.  Con:  Harder to get in large quantities
                 
Electrimod.com - Modular Electronics
Exoge.com - Modular Simplicity

ThantiK

  • FamiLAB Member
  • Full Member
  • *
  • Posts: 237
  • Resident 3D printer guru.
    • View Profile
Re: Rockets!
« Reply #9 on: July 18, 2012, 05:26:56 PM »
I don't know if we have any place for a vertical test stand.  But explosions are bad.  Getting sufficient room for a vertical test stand seems the safest route.


As far as engines go, Liquid Bipropellant + LOX + Kero/Diesel seems the easiest to get materials for.  While the implementation is harder, the calculations, etc are easier and florida heat less of an issue.  Assuming electrimod has the knowledge and can suitably mentor us, I say this is the way to go.

electrimod

  • FamiLAB Member
  • Newbie
  • *
  • Posts: 19
    • View Profile
Re: Rockets!
« Reply #10 on: July 18, 2012, 08:23:14 PM »
I was the advisor on this senior design project
http://www.exoge.com/mambo/content/view/26/46/
I will not say I know everything but it's only rocket science right?
 
Electrimod.com - Modular Electronics
Exoge.com - Modular Simplicity

electrimod

  • FamiLAB Member
  • Newbie
  • *
  • Posts: 19
    • View Profile
Re: Rockets!
« Reply #11 on: July 18, 2012, 08:47:11 PM »
Download and take a look at this program.  It allows you to calculate performance of an engine given some basic information.   We usually use it to estimate the performance of the fuel and oxidizer mixture ratio.
 
http://www.propulsion-analysis.com/downloads.htm
 
Electrimod.com - Modular Electronics
Exoge.com - Modular Simplicity

darkmoonsinger

  • Treasurer
  • Administrator
  • Hero Member
  • *****
  • Posts: 741
  • I am no one but all that I am.
    • View Profile
Re: Rockets!
« Reply #12 on: July 18, 2012, 11:01:06 PM »
Cheers, dude, that beats the spreadsheet that I have that sort of wings it. *g*

electrimod

  • FamiLAB Member
  • Newbie
  • *
  • Posts: 19
    • View Profile
Re: Rockets!
« Reply #13 on: July 20, 2012, 12:23:17 AM »
How about a torch style igniter as a project?  I have built many of them from standard plumbing pieces but I say we machine this one from stock stainless steel.  They are in reality miniature rocket engines because the combustion is inside the chamber unlike a normal torch.  What makes them difficult is they are not cooled so run time is limited.  Another problem is typically they use a gas fuel and oxidizer.  This can be problematic for the math part since a gas is compressible.  Compressible flow is always fun.  Luckily I have already done the spreadsheets years ago.  I even happen to have the neeed K bottles just sitting around doing nothing.  I am sure the oxygen bottle is now empty so I will need to fill it and then propane is just a shelf item at most stores.
 
Electrimod.com - Modular Electronics
Exoge.com - Modular Simplicity

ThantiK

  • FamiLAB Member
  • Full Member
  • *
  • Posts: 237
  • Resident 3D printer guru.
    • View Profile
Re: Rockets!
« Reply #14 on: July 21, 2012, 10:08:31 PM »
Is there an existing design you have in mind?