Monday, December 21, 2015

Flight of 12 19 15

Some background on GPS.... this post is chronologically challenged as it flips back and forth)

I have three approaches to getting the GPS to work.
They are somewhat related.....

1)Use a Swift navigation PIKSI with custom firmware.
I've flown this unit with stock firmware twice, and with custom firmware once.
Flight 1 Stock firmware, lost lock at ~5 gee, marginal GPS in all cases.
Flight 2 Custom firmware with wide open GPS tracking loops... over did it as the units were tracking sats that were not there.....
Flight 3a) (12/19/15)
Newer version of Stock firmware GPS performance much improved, still lost lock at 6 gee, but recovered at burnout...
flight 3b)Same flight different piksi hooked up to intel compute stick to log RAW signals from the front end.

2)Use a RTL SDR dongle with GNSS-SDR and write custom firmware..
Thanks to some help from a follower/friend I have this runnign on the ground with my survey grade 35DB trimble antenna, but not with the flight weight antennas, I'm waingin for some low nosie amps to make this work wiht the flight weight antennas.

3)Build my own GPS with full IMU tight integration.
This will use the same Maxim GPS front end as Piksi, but with the Zynq CPU.
I have all the prototype pieces in work....

After action...

Thursday, Friday and Saturday I had a bad sore throat and cold.
On Thursday I determined that the RTL-SDR was not going to work without the LNA I did not have.
So I switched to trying to record the raw signals from the piksi...
After napping much of the day Friday to get better I finished the Piksi raw record  about midnight Friday.

Saturday I got up at 4:45 rechecked that everything was working, packed all the stuff into the car and drove to the airport.  I took off about 7am in the 182 Headed to FAR , I landed on the private dirt road next to FAR at about 8:15.

Started prepping the HPR for the flight using one of John Newmans ~M experimental motors.
one of the Altimeters failed the deployment charge conductivity test, took me about 2 hours to find the broken wire down inside the avionics module.  Launched the rocket at 11:07:26  It went to ~12K ft. The GPS experiments and batteries added a lot of weight to the nose cone and I did not upgrade the main chute retention nylon bolts. So when the drouge deployed at appogee the main also deployed.   After driving around in  the desert on the quad for an hour gave up looking for the rocket and switched to the airplane.... it took us about 5 min in the 182 to find the rocket. It was 4 miles from launch and withing 25 ft of a paved road.  So we landed back at FAR and Ted took me to get the rocket in his jeep.  Kind of fun to ride in a really capable off road vehicle...  The rocket barely fit in the jeep and on the way back to far we jumped over a rock pile the rocket came loose and broke Ted's window ;-(  When people try to budget projects like this and understand costs no one puts things like Jeep windows in the budget.....

Once back at FAR I took the GPS modules out of the nose cone, I  packed up and flew to Oceanside...(OKB) The flying club I'm part of had its Christmas party Saturday afternoon and I had promised I'd give breezy rides, so I left the 182 at OKB and took the Breezy to CRQ... it was too cold and I had no breezy ride takers.... so I took the breezy back to
OKB put it away and flew the 182 back to CRQ unpacked and drove home.  I got home about 6 pm and went to bed early. It was a long day...

Saturday I downloaded the data from the GPS modules.  The SBP format file  from the first Piksi is here: SBP format Datafile The SBP format is defined here

Decoding that the Piksi with the current stock firmware lost lock at about 6 gee and regained lock at burn out.

The second piksi was recording raw RF from the front end via the intel compute stick... from time to time it had a FPGA fifo error and the sampler would restart.... inside this zip file are a bunch of raw data files.  The file ending in 110731 has the first 4 seconds of flight. The File 110822 has the balance of the boost phase.  

These dat files are supposed to run in the swift nav peregrine software GPS receiver, alas my linux fu is not working and I'm unable to get peregrine working as it looks like swift has moved its library python bindings from a separate module into the libswiftnav, alas that integrated version python will not build on my VM....
If anyone wants to play with this you can find info on peregrine here: Peregrine

That's all for now. I'll update when I manage to get some info from the raw data.

Sunday, December 06, 2015

After Action report...

So this was  a FAR weekend.
I had intended to do three tests, only got one done.

I fired the 3D printed motor with larger diameter plumbing on the main valve and a turbine flow meter so I can measure C* and ISP.

Results are mixed....
The test stand I'm using is an amalgamation of an old test stand and a bunch of valves from the silver ball.  In short it is a mess. I worked on making it better this week. (largely why I only got one of my tests done)  We hydroed the basic structure and tested the relief valve a few weeks ago, and all of that is solid.  The new valves and arrangements form the main outlet to the motor are solid.

The valves for the fuel side and the pressurization system are 100% Silver ball leftovers.
They largely worked two weeks ago when we ran it, this weekend two of the fuel side valves were frozen and the actuators died.  I had one spare actuator with me so I replaced the fuel valve actuator and changed the fuel side vent to manual operations.

The 2nd deficiency of the system is that all the wiring is an unreliable mess. I hope to clean that up repackage the electronics and make it all a solid solution before I use the stand again.
I  left the test stand at FAR but brought all the valves and sensors home.
The actuators are all dynamixel RX-64, 18V actuators  run off a 5 cell lipo and an ac power supply to keep things topped up.  I have a nice 40V  13.8V AC powered supply, thinking about trading the RX-64 for MX-64 that would be happy running at 13.8V. This is a $1K decision, I need to sleep on that.

My old sureflow pump for loading oxidizer died this year. I bought an air powered diaphram pump from McMaster car to replace it as the model of sureflow pump is not longer made.
The problem with this pump is that is really pulses, the flow is not smooth so hoses jump around and do unpredictable things.  I mounted the pump to a 3 hp roll around aircompressor and added a remote dead man switch activated valve to turn the pump on/off.  I also changed the loading procedure form opening the top of the tank to having a separate valve and a hard connection on the bottom for fueling, no ladders involved. These changes mostly worked as designed and I'm happy with them. much less risk drama in oxidizer loading.  I need to do something similar for the fuel side and will do so.  I still have hope that I can find a good steady electric self priming oxidizer pump..... I've ordered a couple of candidates, we will see how they turn out.

The firing ran well about 78 seconds. The CAT pack worked well and I got good data. The feed pressure was up about 20 psi from last time, the chamber pressure was up about 10, not sure where the other 10psi went.... motor ran at about 180 PSI target is 200. On shutdown the fuel feed pressure stayed up witht he fuel valve closed.  So I suspect that rebuilding the fuel side of the system in the mojave dust introduced enough material to clog the fuel orfices.  I've ordered a small sintered 10 micron fuel filter to add to the system.  Well see when I examine the engine this week....

I forgot to do a final last minute tightness check on all the plumbing. Got distracted by a rocket launch that required everyone under cover and for got to tighten one pressure transducer... sprayed peroxide all over everything...this part was after the main valve so was not part of the pre-fill leak check.

Then wheil disassembling things I dumped fuel all over the open ox inlet port on the motor.
So before I run it again it needs to come apart and be properly lcleaned for oxidizer service.

Things to do before next test:
Rebuild and test all the valves and actuators.
Package the electronics in a more robust manner.
Add flow meter to the fuel side.

I'll probably run another motor test the first FAR event of January that should be Jan 2nd
For the Far event on the 19th of December I'm going to try and fly my GPS experiment and test the little TJ-20A turbine as a potential first stage motor.  

I'll try and post some of the test data when I have looked at it later this week.


Friday, November 27, 2015

Working on full layout

Looking at various possible layouts for the bottom of the Third Stage.
(IE the one where weight really matters....)

Friday, November 20, 2015

motor design...

Here is a quick note about the Motor we are going to fire on Saturday...

The Grey is the 3D printed motor.
The Light Blue is the part I turned and machined (4 times)
The Gold is the peroxide going down the cooling passages...
The Red is the peroxide coming back up the cooling passages... (The gold and red connect at the right end of this drawing.
The Green is the Catalyst pack that turns the oxidizer from liquid to Steam and hot Oxygen.
The Yellow in the band around the middle and in (two shown) the four fuel injectors that inject fuel just below the cat pack.

Monday, November 16, 2015

The big chunks...

Trying to do a minimalist amateur sputnik....
We need to build a vehicle light enough with a good enough performance to get to orbit.
We need to make sure we can make it go in the desired direction.
We need to involve the regulatory agency so we can do this legally.

How do these three base requirments break out into bigger tasks...

0)Conceptual Design...
 Spread sheet and simple performance model says 4" diameter 16" long OTRAG tube rocket can get to orbit.

1)High mass ratio Air frame...

  • I have tested representative tanks with the required  mass ratio.

In process:

  • I have one full size sample, I still have to test that.
To do:

  • Finish Detail design of Full Airframe.
  • Static test one full tube with fill drain, gimbal etc...
  • Build Cluster.


  • Designed Motor and had it 3D printed in Aluminum.

In Process:

  •   Finishing hte machined parts to go with the motor, adding cat pack and instrumentaion
  •   Using old Test Stand from 2011

To Do:

  •  Test Motor and refine design, iterate
  • Design and test high expansion ration version.
3)Good high quality vehicle simulation for performance optimization and HIL testing.
 Selected Simulator (JBS Sim) and contracted to have a good initial model built.

In Process:
    Waiting initial model and simulation form person contracted to do the work

To Do:
   Optimize and evolve to full HIL simulator...

4)Build and Code Avionics:
 Pick an archetecture (I think 75% confidence) we will use one of the tiny  pixhawk  clones for avionics.

In Process:
  Find a light weight GPS that will work without co-com limits at high acceleration.
 We have flown Piksi on a HPR twice continue to work on that aspect.

To Do:
   Design the full code set and test in HIL

5)Build and test GSE..
 Conceptual GSE concept that minimizes weight on the airframe.
Uses single "Tube" to fill and pressurize remotely.

 Design airframe QD and ground GSE.
Test Concepts via static tests...

Done Regulatory concept...
  • Will do inital testing at FAR up to 50Kft.
  • Then will do suborbital flights offshore.
  • When time to go over 200K lb/sec or to orbit:
  •      First stage constrained by physics from hitting anything.
  •      2,3,4th stages made of low temperature tolerant composites, so incapable of high speed flight in the atmosphere.
In Process:

To Do:
    Start discussion with FAA for orbital licensing requirements.

Saturday, November 14, 2015

Today's progress...

Spent the first half of the day cleaning the shop.... I have way too much stuff.

Then I machined the soft jaws of the three jaw chuck to grip the end of the 3D printed motors...

Then machined

Thursday, November 12, 2015

Jet Packs... aerodynamics questions and thoughts....

If you follow such things the Jet pack from  was subject to all geek discussion last week. Today I say an article here:

This describes the controls of the jet pack.....

Notice that the only video we have seen is of it flying somewhat low over water. This means in the mind of the designer its not safe over anything hard.

There is pitch and yaw control, but no roll control other than weight shift.
To me this means that the output from the two jet engines must be really closely matched.
Loose either  engine to something as simple as an air bubble in a fuel line and your spinning wildly out of control.

So how would you build a safe useful jet pack?

Minor expected faults won't kill you.
Single engine, sensor or actuator failures wont kill you.

Able to fly at whatever altitude fuel will allow over any surface.

In my mind a safe useful jetpack would have the following:

Flyby wire artificial stability.
Engine out failure recovery from any altitude.
Safe escape from and single engine,sensor  battery or actuator failure.

This implies to me multiple engines with some kind of thrust vector control.
You need enough  control authority to maintain stability with one engine out.
You need enough control authority to maintain stability with one actuator or motor in hard over failure.

You don't have to always land, you can have failure induce a rapid climb to an altitude that ballistic parachute can deploy. (300 ft or so)

Rather than two motors I would think at least two per side. This means that if you loose an engine on one side all of the the other engines must have enough control authority to keep thrusting through the center of mass.  If the control authority point is above the CG (like their jetpack) then the gimbal on the good side will have to point toward the passengers legs, probably frying them.  To me this imples that the jet point of thrust vector control must be below the CG. IE the jets must move down on the human.  Then the thrust vector to compensate for rolling (or pitching) moment from a failure on the other side would point away from the pilot.  It also implies that each side have enough thrust so that if 1 motor fails it can hold up its side......

So I see something like 3, 4, or 5  smaller motors per side.

With 5 motors a side I believe you might be able to control the vehicle with just thrust throttling...

If you need thrust vectoring then a flap that you can deploy into the exhaust stream that deflects it in the  direction of the semi circle away from the pilot.

In thinking about things one of the scariest failures would be bearing failure where the motor dumps all its built up momentum in the free flying vehicle as its thrust goes away.....

I just don't see how the Jetpackaviation jet pack we have all recently seen could be made "safe" for flight over hard surfaces.

Some random observations:

From their images JB-8 was more of a flying sled. Its real clear that the JB-8 used two TT-100 247lb thrust jets, the same as the sonix jet uses.  These are about 50K each.

Its also clear that the JB-9 uses two smaller engines... AMT Nike motors.(24K Euro each)  I wonder if the motors  counter-rotate, or if they don't how much rolling moment pitch changes make given the gyro coupling.... since the  designer and test pilot are both helicopter pilots they will be very familiar with the 90 gyro force motion phase shift....

In looking at the middle of their three videos the "Gopro" one that they are using standard box stock RC turbine ECU displays for the engines mounted on the stick grips, these displays are on the tether flight video, but not the NY harbor one... or the promotional jet pack pictures.

On the tether flight video one can clearly see a large LIPO battery pack connected to the engine ECU under the cover.

Also in the NY harbor video there looks like an added frame to keep the tether training cable from getting wound around the pilots head....

Needless to say I want one...

P.S. I want to see their blooper reel...
Edited to add info on what motors they are using.

Monday, July 20, 2015

GPS on several fronts...

This week end I flew an open source Piksi GPS on an HPR to see if it could be made to keep
lock at high acceleration without any imu aiding. I modified the tracking constants of the piksi software .(actually used # defined for wide bandwidth tracking already in the latest software)

It lost lock at boost, got lock again at apogee (strong winds at FAR apogee horizontal V was 204knots!)  This pulled the electronics bay out of the vehicle when the drogue deployed at that speed.  Fortunately its a sturdy rocket and it survived a no main chute deploy with minor damage.

There were some issues I think I set the lock detection too too optimistic and it tracked some noise...
I will fly a Piksi again recording the Raw RF some time in early Aug.
(I'm also going to change out the TCXO for one with lower G sensitivity see discussion below)

On a 2nd GPS front PSAS flew a software GPS receiver on their rocket on Sunday.
They gathered raw data, but they don't have the full GPS solution working yet.
They posted the following graph

It shows doppler shift in the tracked sats.
I actually question that a little bit...

Doppler is what makes a trains whistle change tone as if goes past.
If you change the velocity with respect to a radio transmitter the frequency will shift.

There is another effect that can also effect this data... the RF system on a GPS uses a very precise clock (usually a TXCO)  in the receiver.  That clock may have acceleration sensitivity.
IE the frequency of this oscillator may vary with applied acceleration...

I'm somewhat suspicious that the graph above shows this more than Doppler shift.
I have not looked up the orbits of the gps sats at the time of flight or the position of PSAS flight, but I'll make some assumptions...

The GPS sats are scattered randomly about, ie some are almost straight up and some are at the horizon.  If the rocket flies straight up one would expect a bigger doppler shift for the sat straight over head and much less shift for the sats at the horizon as their relative velocity changes less.
Also if the rocket turns into the wind and has some horizontal velocity one might even expect a doppler shift in the other direction for the sat you are flying toward/away from.

However if the frequency shift is due to g effects on the reference clock one would expect all the doppler shifts to move the same direction....

So it looks like they got a shift of about 1400 hz  at 1.5Ghz that would be a velocity of  140 m/sec or so... at 1.5 Ghz. So the magnitude is withing the realm of possibility...

(The graph also shows an overshoot at the end of the rocket burn this is the acceleration changing direction from the perspective of the GPS receiver.)

There are vendors that specifically sell clock oscillators with low G sensitivity...

Given their data the PSAS should be able to determine this.
With a full GPS solution derived from the data (they have not done this yet)
They will get position velocity and time....
They also have sample of data precisely clocked out via their reference oscillator...
The difference between the time in the solution and the time via their local clock can
be measured and will give an idea of clock drift.

They can also calculate the expected doppler between them and the individual sats and see how that compares with the   measured doppler any difference is clock error...

All of these data extractions require they get a full solution running....

There is a quick and dirty test they can do with just what they have...

Run their gps sampler system on the ground with a fixed  stationary antenna...

Now take the GPS board and orient it it differently in the 1g gravity field.
6 combinations IE board component side up, component side down, tipped on its end, pointing up, down right left....

 and generate the doppler graph above...  if the doppler shifts with orientation of the sampler board then they probably need a more stable clock.

  At  bare minimum this test will show them what axis has the lowest clock sensitivity....

In any case I really applaud what the PSAS guys are doing!

Monday, July 06, 2015


Over the last two weeks John and I have built and failed 10 or so short tank samples.
We have a tank solution... fully allocated with fittings and end caps we have a MR of about
15 at 795 PSI burst. (16 at 500 psi)

Now we have to put together the tooling to make flight length tanks , ie longer than the samples.

I did a 3d printed regen motor design and sent off to have a SLS nylon version printed to evaluate.
That should be here today.

Not sure if I want to put gimbal at the nozzle (as test print) or up at the top of the motor...
Been busy....

Tuesday, June 16, 2015

Tanks again

I finished fabricating all the parts for the tank test V2.
I should be able to assemble and test this evening.
This is a short piece of test carbon tube with reinforced ends for additional load bearing,
The end caps are 0.075" domes with AN-8 o-ring ports on them.  The outside of the dome had to be cut with two different cutting tools, so you can see a line/step of about 0.010" where I changed tools.

Update I put it all together and hydro tested it this evening.
It failed at about 850PSI.  The bag and end caps leaked profusely until about 300psi when the o-rings seated. At 500 PSI it held pressure with zero leakage.  The primary failure seemed to be a radial  split down the center.


Wednesday, June 10, 2015

Slightly OT How to get from old world to new world (parts and vendors)

Twenty years ago everything slightly technical came through a distributor that provided technical support.  Today the internet is a source of that support, so what function does the distributor provide?

I was looking to buy some tooling for my lathe. (Names not included to protect the innocent)
I found the exact thing I wanted where a vendor had a nice description of how to use the tool and had captured the exact thing I was looking for...

I emailed the vendor, they entered my information in their system and one of their technical people provided me with a quote and some nice technical information on the proper usage of the part....

So far we are happy everything is golden....

The problem is there was no way to order the part.  On their website their was a list of 29 distributors for their stuff in CA.  I called one at 2:15 pm they said the factory is closed I can't get you delivery info.... I'll call you back on Wedensday.... After some more searching I found no on-line vendor for this "Exactly what I wanted part"  So I went to MSC direct and figured out what I needed to order to do the job, probably not as well as the part I wanted, but I placed the order  at 4:59 pm.

Today I received a call back from the distributor at 1:15 pm saying the part was not in stock.
I got the parts from MSC delivered to my house (UPS ground from NV) at 1:57pm.

So here is a vendor with good marketing an a quality product that failed to make the sale.
Why?  They aren't stupid they know this process is killing them why no online ordering or stock check?

They are a successful company that was actually profitable and doing well before the internet.  100% of their revenue comes via distribution and if they open an online store they kill all their distributors and loose most of their existing business flow.   If they offer their product line through some existing on-line distributor they upset all of their existing customers. Its sad, but they are trapped.

In my day to day life I see a lot of these....

Its one of the things that's changing in the world,  it takes a lot less people to run a few centralized where houses set up to ship quickly than it does to have a real human at a distributor in every city.

Just this past weekend our dryer died, in years past this would have involved a drive down to the appliance parts store in Chula Vista on Monday morning..... This time I ordered a new dryer belt from amazon Saturday at 9PM and had it at 9:30am Monday morning.

The internet and automation is going to eat a lot more jobs before its done. Its not just automation replacing specific workers, its a new structure of doing business that is decimating a whole layer in the supply chain that used to employ millions of people.  May you live in interesting times...

Tuesday, June 09, 2015


One of the failings of silver ball was that I never got an accurate hardware in the loop simulator running.
On this project I'm not going to make the same error. 

After evaluating a number of possible solutions I've decided to use JSBSim  and I've secured the assistance of the 
Jon Berndt,  Development coordinator and chief architect for the JSBSIM, in getting that done. (I've made an arrangement where he will help me get started for a consulting fee, his time permitting)

One of my questions to him was:

>A details question.... I realize that JSBSim was built to be a flight simulator.
>I'm trying to repurpose it as a rocket simulator....

>Internally you seem to use ECEF coordinates.... I have not dug deep enough to figure out 
>if you model the inertial effects of a rotating earth...
>will one see a performance difference between an equatorial launch and aa polar launch?

>If I have a vehicle attached to the surface of the earth will it show the rotation rates of 0, or will it show the 
>the rotations rates one would see in an Earth centered inertial frame?

His answer greatly increased my confidence that I made the correct selection...
And, yes, JSBSim had a full overhaul of its EOM many years ago for full and complete EOM. It was the only non-NASA sim used in a large check case development effort that is published here:

The EOM integration takes place in ECI, full rotation effects are factored in and – yes – you would see the benefit from an equatorial launch compared to a higher-latitude launch. It is a full, vehicle simulator that can model anything from a rocket to a ball to a blimp to a sub/supersonic aircraft.

The vehicle sitting on the launch pad should show no Earth relative motion, but should show a translation and rotation relative to inertial. This was one aspect that was compared across NASA sims and JSBSim in the check case effort, and the comparison effort investigated tiny differences to make sure we were all on the same page and using the same Earth rotation rate. At this stage, I am very confident in JSBSim. That’s one nice thing about open source and broad use: the more people use it in different ways, the better the development effort goes, and the more robust the code becomes.

The simulator in general is designed to be data driven via external XML files. So one can model things like autopilot loops etc...I really want this to be a hardware in loop simulator so one of the modifications I'm asking Jon to help me put my c/c++ code into  the control loop. Eventually this will entail me taking the current state, simulating the IMU and GPS outputs feeding it into flight avionics and then taking the response from the flight avionics and giving it back to the sim to have it operate on the commanded changes.

Monday, June 08, 2015

Update on the week...

During the week I got my "paper" 4" otrag rocket to orbit.
This was a 2D rotating earth model including blow down pressure effects and atmospheric drag.
I assumed drag was the same as a sphere with the same frontal area as my otrag stack.
This was from 30deg latitude.

The classic otrag square 4:12:20, triangle otrag 3:12:20  and single tube last stage 1:6:12 all got to orbit. The single tube unit had the most margin.

I broke the trajectory into 2 segments for first and 2nd stage and 3 for third then did a brute force search of the space for optimum trajectory.... where my optimization fitness was horizontal velocity at 250Km with vertical velocity >=0.

I have a couple of other people doing modeling to "check my work" Ed Lebouthillier is one of the people helping me check my work with performance sims.  He put together the following picture...

I also reopened a discussion with the FAA on what it takes to do part 101 launches offshore...
and got a really favorable answer. On their request I'll publish more when the FAA resolves one remaining question. (Its really good news in any case)

Friday I got and assembled the pieces for a sunlight readable laptop... (pixel QI 10.1" screen and Samsung netbook) and swapped screens. Tested this in the Mojave on Saturday and it worked well.

Saturday I went out to FAR and almost finished cleaning up the old propellant.
This involved using a large "can opener" to open the tops of drums, removing the poly liner and getting the drums recycled.  The down side is that the can opener only works on about 50% of the drums. For the rest of the drums removal involved a  45 minutes, a cold chisel and a small sledge hammer... Did 9, have 5 left.

While I was at FAR I picked up a new carbon tube from John, with end reinforcement for better end cap retention at the desired 4" size. Will test this tank some time this week when I finish machining the end caps.

How to attach your plumbing to fabricated parts is always a challenge. With welded tanks we just welded on AN bungs.  But if your going for minimum weight welding really destroys the aluminum strength.  So the two remaining choices are machine AN fittings directly into the aluminum or put in an AN o-ring sealed port. Bought a port reaming tool and tried that Sunday night...
The tailstock on my lathe is a replacement and about 0.010" too high, with no adjustment.  So this caused the super rigid port reaming tool to chatter  screwed up the bore leading to bad threads... so I'll make another end cap tonight and probably do the port machining on the mill where I can indicate in center....

I may take the tailstock apart and try to machine off 0.010 between the base and the tail stock...
Need to set up to fully indicate the tailstock quill to see if its just too high or has parallel issues as well. (Quick run out test says parallel is ok and its just too high.)

Next up is to farther flesh out the detailed design of the paper rocket with respect to fill and drain, valves and gimbal actuators...

I'll try to post something at least once a week....

FAR has another event in two weeks, I may try to fly a PIKSI on my HPR to see how well it holds lock with with acceleration.

That's all for this week in unreasonable rocket land.

Sunday, May 31, 2015

Quick tank update...

The goal for the composite tanks are 250PSI operating 500 psi design burst and 375psi qualification.
Today the tank I tested failed at 375psi.  When I blew one end out, I did not re-bond the opposite end, the opposie end then failed. (Sort of expected)  When it failed it also split lengthwise.

John is gong to make me some new tubes to test.. with a peel ply layer at the bonding ends and an additional layer on the ends for additional strength on the end caps.
We may add enough material to have bolted ends as that allows you to disassemble and inspect etc...

I also need to slightly rework my seals as the tank seeped until the pressure came up and the seals seated hard. (IE it seeped at 50psi, but stopped at 125 or so)

The current conceptual launcher uses bundles of 4" tanks so the next tube samples will be 4" The current sample is 3"

Thursday, May 28, 2015

hardware again...

My  current concept for a flight weight tank is a carbon tube with a poly liner inside.
I machined some end caps and John Newman gave me a flight weight carbon tube.
The first test failed because the retainer plug on the end had the glue fail, so I sanded the area better and I'm waiting for the glue to dry to try again.

Thats hardware project #1.   hardware project #2 was my idea, but the majority of the work was done by Monroe King.  its the spectra operated valve concept I posted about a week or two ago.  Monroe machined a beautiful valve and I then proceeded to make it ugly. First I just used a 1/4 20 bolt with a slot cut in the head and  filed smooth for the retaining rod.   Second I needed 8 fittings to get from the 1" diameter valve body to the right fitting for my hydro tester. I also did not have any nicrome wire so I used some 0.032 stainless safety wire instead. Attached is a you tube video of the successful valve test...

Wednesday, May 27, 2015

What follows below is a "mind map" I put together 2 weeks ago to think about how to get to orbit.
Not every leaf of every branch needs to be evaluated. On some branches I only need one leaf to work the other can be abandoned.
The currently Active leaf's are Red

Decision Tree
Tank Technology:
Welded Aluminum
Irrigation Tube
HP 6061
Rolled Sheet
Electroformed Sphere
Wellmate Stock (Acquired samples)
Wellmate Re-wound
PET Stock/Reblown (acquired large PET bottles)
Pet Reblown inside Shell
RotoMolded in shell
Poly Bag Liner Test hardware has been fabricated

3D printed Regen
Aluminm A motor design was quickly done and sent out for quote. 3D printed price was acceptable. More than 3:1 variance in differnt vendors.
Fabricated Regen
Plated close
Saddle Jacket
Poly Heat Shring
Poly Cast
AL Tube?
HP Solid for Last stage Asked one of my solid friends to look at this.
GPS Selection
Piksi If we have a GPS it will likely be this.
Fiber  (ordered surplus fiber gyro from ebay wil use to evaluate different mems sensors.)

Presurization System
Blowdown with one intermediate valve
Liquid nitrous
       Presurized bottle and regulator.(If our composite tank ideas work as well as they seem to then this is not really a win as the blowdown tank tech from a mass standpoint is almost as good as hightech carbon wound presurant bottle.

PayLoad  (Cubesats have used CC1100 based radios to communicate so its a reasonable choice)
CC1100 based Custom
BigRedBee I have one of their 70cm tranmitters in hand, payload < 50gms possible.

Architecture trades
Custom C++
Trajectory Design
Custom C++
JSBSim (I think I've secured some help here that is very familiar with JSBSim) 
Control Laws higher fidelity sim
Hardware in Loop Testing
Mission Design
Wild Ideas
  Jet Lifter
Propellant Selection
Pressurant Burining?
Launch Location (Within in a month when the archetectures starts to shake out its time to go to FAA and start discussing this)
On a Boat?
On a Plane?
Traditional Range?
NM Space Port?
Space Fl?
Intermediate Testing
Limits to what can be tested at FAR?

Monday, May 18, 2015

Rocket Motors...

In an ideal world I'd just have the rocket motors 3D printed.
I believe (I've sent out a sample file to be quoted) that they will be prohibitively expensive.

If I could figure out how to make shapeways 3D printed metal parts work that might be affordable.
(Long time followers will recall that the shapeways process does not work for internal cooling passages, so the inner and outer need to be assembled from separate parts, and if you then weld them together they get porous as the high welding temperature drives out the brass used to infuse the stainless powder.)

So one of the tests that I might do is to see if I could  make a 3D printed rocket design that Shapways could make, then I would solder or low temp braze the outer shell over the motor.
Another possibility might be to plate the resultant leaky welded motor ... a number of things to try...

One could always build saddle jacket motors.

Friday, May 15, 2015

Another way....

Low cost access to space.....
Many believe that reusable vehicles will ultimately give us  low cost access to space. The Shuttle was supposed to do this.  Spacex is rapidly approaching this goal with the first stage. I  assume that once the 1st stage is recovered they will soon try to recover 2nd stages, capsules, solar panels, trunks, payload fairings, all the way down to minutiae like GSE cables and dust covers. The eventual goal being airline like reuse. This will eventually lead to a beautifully refined optimized jewel like perfectly executed complex space launch system.  Every component will be reusable, repairable, refurbishable .

Right now if a vacuum Merlin has a bad day you loose the whole mission. In the airline industry engine failures are a regular occurrence, but since they have robust intact abort capability and procedures we don't hear about it. If a rocket is going to achieve airline like  operations it will need this capability as well.   Once the value of the reusable vehicle is as great or  greater than the payload intact abort gets even more compelling.

Some large helicopter systems may require 60 hrs of maintenance for  every flight hour.
How much maintenance will a reusable space craft require?

Amortizing the cost of developing the reusable space craft will need to be recovered, fixed and variable operations costs, rebuild and overhaul costs etc.... etc... etc... all of this will need to be covered.  Suppose spacex does 100 flights a year and the rocket is 100% reusable and propellant is free....  They currently have ~4000  employees this means with all other costs at zero the standing army at 100 launches a year will cost $4M a launch if everything else was free.

Even with this best case scenario this is a long path and with chemical propulsion the gravity well is deep.

I can buy any number of Rolex watches (lowest cost on on the page is $31K) .  I expect it to be a fine example of swiss craftsmanship. If it ever breaks or misbehaves it will be delicately repaired by a skilled artisan.  It will be a family heirloom for generations to come. If I go on amazon I can find digital watches starting at $3. By my estimation the $3 digital watch probably keeps time as well as the very best all mechanical Rolex. (For an apples to apples comparison the lowest cost mechanical watch I could find is $20.00)
No one is going to repair a $3 watch, you just throw it out and get another. Even if you think throwing it out is wasteful, is it really more wasteful than the standing army of rolex dealers and repair centers that stand behind the use forever rolex?

With the early microcomputer , all of the chips, and boards were replaceable. If a ram chip died it would be individually replaced.  Now the fabrication is so cheap dead motherboards go to scrap. No one seriously considers repairing them.  (Amazon lists 28,000 motherboards under $25.00)

What if space craft were so cheap that if one failed it wasn't a big deal? You just launched another one...My guess is that if there is a production failure on the $3 digitial watch they do no rework.
For some kinds of cargo this is not acceptable (Humans for instance)

My friend Joe Caroll has a saying to reduce the cost of space we need reusable rockets, or reusable rocket factories.  Without reuse things just get simpler. At some point if you can build them cheap enough in an automated way, expendable is cheaper than reusable.(How may of you gray hairs remember TV repair shops?)

A rocket is a complex item with first, second,  third stages, different engines,tanks, fittings etc...Each one optimized, a reusable rocket factory will need a flight rate high enough to justify this factory. If your only building 10 a year does it make sense to build a fully automated factory? How about 640?  You will use a lot more automation building 640 than you will building 10.

This brings me to my favorite rocket that almost was, OTRAG See here, here and here. Each 1 Ton rocket had 64 identical Common Rocket Propulsion Units  (CRPU) . Each otrag CRPU had one moving element a single ganged on-off throttle valve.

One of the concepts I've personally explored for a small launcher is an  otrag launcher sized to launch a 3U cube sat.    Instead of having to design 3 stages with 3 different  tanks, valves, motors,  fill ports, testing procedures and handling and transport I only need to design one. I can spend three times as much in optimizing each  element and still be ahead. To be fair they are not identical, you would probably have to hack saw off the nozzle on the "First" stage, and the pressure to do additional lightening on the upper stage would be extreme Some ways this could shake out, a common blowmold liner for tanks with upper stages wound with carbon and lower stages wound with glass....

Also the increased drag and many of the square/cube scaling issues that are bad for Otrag are much worse for a nano-otrag.

Monday, May 11, 2015

Concept for a light weight clean electrically actuated valve.

Pyro valves have(an article written my Tom Mueller on amateur pyro valves) a long history in rocketry. The problem is they are not very reusable and for the amateur testing them and maintaining the system cleanliness necessary for a peroxide oxidizer are challenges.

One of the strongest man made fibers is Spectra or Dyema. One problem with spectra is that is very weak at elevated temperatures.   Here is my concept on using this to make an electrically actuated valve:

The golden thread is a Spectra loop with some nicrome wire wound in it.  Hit the nicrome with a electrical current it gets hot and the spectra fails.

Here is a split view of the closed valve:

When the spectra fails the purple plunger is released and the blue piston moves down the fitting. The purple plunger guides the piston to keep is from cocking while it moves down. When it hits bottom the purple piston falls away.  Here is a split view of the open valve. 

Not sure if this will work, but some time in the next few weeks I will fabricate a test article.

Friday, May 08, 2015

Waking up from a long slumber.

A Story in many parts...

I've been searching for a good rocketry project. The one I really want to do is start up a nano sat launcher business.  Every person I presented my business plan to had the same response, no way you can build a successful  orbital launcher for lest than $XX million dollars. Everyone's XX was different but they were all  at least two digits.

I was not planning to go to SpaceAccess this year.  I had nothing to present and I felt I know what most of the people presenting were going to present and felt the whole thing would be somewhat depressing watching power point after power point saying we are going to fly real hardware "real soon" With the exception of the few groups building real hardware (all of which I have personal friends on the inside) One sees same slides every year with different logos on it, and dam little real hardware.   My wife was visiting her sister in Canada and I woke up Friday morning feeling like maybe I should go to SA15 after all.   The hotel still had rooms for Firday night so after work I borrowed by friend Jeff's Mooney and flew myself to Space Access. (all of my airplanes were rented ).  A lot of people were really happy to see me. After 5 years it still amazes me the impact that my little garage project called "unreasonable rocket" has had on people.  One of the people I was looking forward to seeing at Space Access was Charles Pooley... he did not attend, more on that later.
I did not watch many space access presentations, I spent far more time sitting outside talking to people. One subject of discussion was what I call amateur sputnik, ie what would it take for an "amateur" group to orbit the equivalent of sputnik, ie  the smallest radio transmitter that can be easily detected on the ground.

After returning to San Diego several of us were worried about why Charles had not come to Space Access and why he did not answer his phone. On Monday we learned that he had died in his apartment.  Charles was in his mid seventies and had spent countless hours helping my son and I on the unreasonable rocket project.   He had a vision for small launchers that he and Ed Labouthiller turned into a book (MicroLaunchers). While I disagree with some of his technical designs  (I felt they were too complicated) and disagreed with reluctance to use computers, I did agree with most of the big concepts in Charles microlauncher concept.

I'm I'll be 53 this year, not young, not old, sort of in that neither region were I can see both camps and hints of inevitable entropy introduce themselves to you most mornings.  In the past past three years I've lost my Dad, My Step Mom and my Step Grandmother.  Seeing Charles dream extinguished without a real shot at doing it was just another sign pointing at the impermanence of life.

Building an orbital vehicle is om my bucket list, so all of this adds up to the inevitable question if   not now when. So I guess its now.  In the last week I've started several balls rolling, I have 4 or 5 concepts for composite flight weight tanks.

  1. Our previous flight weight tanks had liner leakage problems dues to bad resin, the trial batch of resin worked the 55gal special order did not. . One of my new  concepts is to build unlined tanks, then take them to a roto-molder and have the insides coated with polyethylene. 
  2. We tried to re-blow a large PET bottle and then cover it in carbon. The fact that we did this as two seperate steps made the resulting tank too heavy as there were fillers and excess to match the carbon support to the liner.  So the current concept is to make a flight weight high temperature composite cover for the PET bottle and then blow the bottel into the flight weight shell in a single step.
  3. I've had the concept of a long composite tubes lined with polyethelene heat sealing bag and high quality machined aluminum end caps.
  4. For a vacuum stage the pet bottle is almost good enough all by itself. So one concept is to just provide a tiny bit of carbon enforcement to the stock pet bottle around its girth and use that as a 100 psi tank.
I've restarted my tank project so that in the next few months I should have at least one of each of these concepts to test.

Additionally if these don't work I have two more concepts to try:

  1. Take a aluminum an tank form. Have it powder coated with thick clear powder coat.Wind a carbon shell over that. Use Lye do dissolve out the inner aluminum shell leaving a carbon shell with thin uniform poly liner.
  2. Wellmate makes really light poly lined fiberglass water tanks for residential use. I used one of their tanks as the fuel tank on silver.  They are almost flight weight as a stock COTS item.  One coudl do much development work with the stock tanks and for the final flight weight version one could aquire the un wrapped liners and wind carbon instead of eglass over them and.

In addition to restarting the airframe tank work I've started the ball rolling to get some fresh propellant delivered to FAR.

In the very short term I need to get my Garage cleaned up, I'm just going to pack and remove anything not rocket related and put it in storage.

Over the next month I will formulate a plan, a rough schedule and list of tasks.  Many people have offered to help, some have almost begged me to organize an effort they can participate in. 
I'm not good at delegation I like to get in there and do it myself, if this is going to work I will need to work on that. At the same time having the project turn into a free for all doesn't work either.

Some things I know I will need help with:

  • I need the smallest transmitter that can be detected on the ground and last for at least a week with batteries, it can have solar panels if they are lighter.
  • The current notional concept has a guided 2nd (or 2rd) stage that points, spins up and ignites an unguided solid final stage that puts the  transmitter in orbit. I think I need someone that can build a final stage high mass fraction solid to be the final stage, I think I have someone for this, but if this is your area of expertise I'm open for talks.
  • I need someone to help me put together a good simulation  ie to simulate the rocket getting to orbit. And hopefully to eventually do hardware in the loop simulation...
  • I'll need help on GNC, I can do GNC hardware and understand the concepts, but my GNC stuff was not great.
  • I need someone local to help video,photograph and blog things.
  • I will need help at FAR (two people) twice a month starting in September for at least a year.
  • I need someone that likes data, I gathered lots of test data in my last effort, I just never found the time to take this gathered data and put into presentable form, ie I'll provide a file of raw sensor data... it would be nice if this could be calibrated, trimmed to show the interesting parts and put in nice graphical form....
  • I need someone that likes to fabricate things.... to help with some of the development. For example I have some concepts for really light robust actuated valves, I could spend three weekends fabricating several sets, or I could spend an hour or two describing the concept to someone and let them fabricate and test. 
  • If someone wants to own the FAA part of this project I'm not sure its possible to deligate this, but I'm open to suggestions...
  • I'm open for someone that might want to help raise social media funds, ie kickstarter, indigogo, subscription access to the progress blog two weeks early etc... so anyone with ideas or a desire to do this would be helpful.
If you see anything on this list you want to help with, or other ideas you think you can help with 
I'm more than willing to entertain the idea.  At this point this is an amateur not for profit project to get something tiny in orbit. When that succeeds I will want to turn it into a proper business, how to give the volunteers involved with this project a share and value in the follow on potential company is something to be worked out upfront and I'm open to ideas.

In the next few weeks I'll do follow on posts with an outline of the notional vehicle,  and a number of the detail concepts that I am in the process of fleshing out.