Tuesday, 29 May 2012

DH-1 Dimensions

In preparation for making a CFD model in OpenFOAM, I have put together a drawing showing the main dimensions of the combined stage 1 and stage 2 vehicle. This gives me the data points to create a 2D model.

DH-1 Dimensions

Wednesday, 23 May 2012

CADAC Variable Locations

In the Fortran code for the CADAC4 software, variables are defined with a specific location. The number range is in the manual, however which variables are stored in which number location is not summarised. To help with this I wrote a Perl script to scan all the Fortran user modules and put together a list of all the names and locations. This helps me to know which spots are free for adding my own code, and means that if I do use a parameter it will have the same location.

CADAC4 Variable Locations

Updated Rocket Engine Data

I have been working on updating my summary of Rocket Engine Data. I have added in the Russian RD-192 engine, as it is about the right size for the main boost engine for the DH-1. I have been trying to find as much data on this as I can, because it runs on the Methane/LOX mixture which is of interest for the first stage.

I am also working on trying to get the OpenFOAM CFD software installed to try and get some basic numbers for the drag coefficients. At the moment the CADAC software is using the same coefficients from the basic sounding rocket example. Also the thrust calculation is a bit wrong because it assumes the exit pressure of the rocket will be the atmospheric pressure (Pe = Patm). However this is not the case especially for the sustainer RL-10A-4 engines.

Thursday, 26 April 2012

Pictures of the DH-1

Using the dimensions specified in the book, I have put together a quick CAD model of what the DH-1 would look like. This is useful to get a feel for the size of the structure, and by putting a manikin into the scene it also gives an idea of the actual space inside as well. I will be working on this over time to improve it, but for now this is what I anticipate a fully reusable, two stage space launch vehicle to look like!

DH-1 Both stages. The porthole for 1st stage cabin is visible between the two jet engine pods
View from the rear. The 3 large purple objects are the main boost engines.

A closeup of the 2nd stage cabin area. The curved base of the heat shield, and the cutout for the boost motor are shown. The fuel tank for the second stage would be in this lower part of the structure.
Side profile of the first and second stages together. The manikin shows where the second stage cabin area would be between the two planes.


The two input files for the ROCKET.EXE executable are the HEAD.ASC and the CADIN.ASC. The HEAD file looks something like this:

      51    REARTH       E Radius of the Earth = 6370987 - m
      52    CRAD         E Conversion factor = 57.29577951 (Deg/Rad)
      54    AGRAV        E Acceleration due to gravity @ sea level             =
      58    WEII3        E Earth Angular rotation = 7.2921154E-5 (rad/s)
     200    MAIR         D =0:Std Atmosphere, =1: Weather Deck
     201    TEMPK        G Atmospheric temperature - degK
     202    PRESS        O Atmospheric pressure - Pa
     203    RHO          O Atmospheric density - kg/m^3
     204    VSOUND       G Sonic speed - m/sec
 *   205    GRAV         O Gravity acceleration - m/s^2
     206    VMACH        O Mach number of rocket - ND
     207    PDYNMC       G Dynamic Pressure - Pa
    1200    MAERO        D =|MAERT|MAERV|, MAERT=1:Type, MAERV:Stage #
 *  1201    CD           O Drag coefficient - ND
 *  1202    CL           O Lift coefficient - ND
    1203    ALPHAX       D Angle of attack - deg
 *  1206    CA           G Axial force coefficient - ND

The original file is generated from the MKHEAD3.EXE program parsing the MODULE.FOR code and extracting all the parameters. However in order to get some output from the run, some of these parameters need to be marked as outputs. This is done by putting an asterisk ('*') in the second column. If there is no asterisk then this variable is not written to the TRAJ.ASC output file.

Tuesday, 24 April 2012

Finding Customers for Aerospace Startups

The hardest part of developing reusable launch vehicles isn't the engineering work. It is because there are no customers for the vehicle when it is designed, built, and tested. This week I was watching the YouTube video Why Accountants Don't Run Startups: Steve Blank. Although the lecture was about technology and Internet startups, the most interesting point was about finding the right business model through testing assumptions about customers and then rapidly pivoting in a new direction as new insights came through. By remaining flexible in the early stages of the search, the direction of the company and the product can be adjusted rapidly to find a profitable business model.

This contrasts with the way in which people have searched for ways to enable low cost access to space. The focus has been completely on the engineering model and technical design. The lack of customers has been assumed to be a problem which will be solved once the brilliance of the chosen approach becomes obvious. However if we take a leaf out of the Steve Blank "Customer Development" model, then we should not start with the engineering but rather with the customers. We need to find what the customers want, and even who they are, before we spend the money doing the engineering.

This is incredibly difficult because there are no customers out there. The customers for the new type of launch vehicle will be companies and business models which also dont exist yet. There is one new option though: Planetary Resources. The announcement that this new company will be working towards mining asteroids means that there is at least one customer in the medium to long term who will be looking for lots of low cost launches. If they develop as planned then this will particularly be the case once they start looking at launching the robotics necessary to actually do the mining. This will be a significant amount of payload the be launched.

So now the question is, can we build the DH-1 so that it meets the future requirements that Planetary Resources will have for their payloads? Since their plan is to use robotics and not manned missions, then on first reading it seems like the compromises made in the design of the DH-1 will be acceptable. This is to do with the size and shape and location of the payload bay.

If we could get some funding to map out further how the DH-1 would work, and at the same time be building links with the Planetary Resources guys to feed the information back then it may be possible to use this new option as the main launch customer for the DH-1.

Tuesday, 10 April 2012

RL-10 Engine Data

One of the proposed rocket engines used in the DH-1 is the RL-10. To help get some good figures, I have used a summary of data about this engine, along with a few further figures on mass flow rates and the characteristic velocity. These numbers will be used in the simulations to make sure that the thrust and mass flow rates used are correct.

Rocket Engine Data

DH-1 Flight Profile

This document shows what the flight profile of the DH-1 will be for both the first and second stages. I am slowly filling in the numbers for height, speed, weight, etc as I complete the analysis using CADAC4. Updated versions of this will be posted as I get some good figures.

DH-1 Flight Profile

Monday, 9 April 2012

CADAC4 Software

I have been learning to use the CADAC4 software, which is available for download from the AIAA or as part of the self study CD:

Fundamentals of Six Degrees of Freedom Aerospace Simulation and Analysis in FORTRAN and C++

Library of Flight
2004, CD ROM
ISBN: 9781563476907
The Fortran version of the software is available from the AIAA. However I found there were a few issues when using the code under Windows and compiling with Gnu Fortran (gfortran). To fix this I had to edit some of the files especially to do with reading and opening files. I will upload the corrected versions of these files here.

Reference link: http://arc.aiaa.org/doi/book/10.2514/4.102523


Monday, 26 March 2012

DH-1 Detail Data

DH-1 Detail Data

I have put together some summaries of all the relevant figures for the DH-1 vehicle as per the data in the book. In the version I have the are some inconsistencies with the figures used so this puts it all together to make it clear.

DH-1 Detail Data 

Thursday, 22 March 2012

Why Does Space Inspire Us

I have just been reading more about SpaceX and this clip from Elon Musk is very useful. Why Does Space Inspire Us - Elon Musk

The Rocket Company Book

This book was the one which finally confirmed to me that it was actually possible to engineer a space launch vehicle which was low cost and fully reusable. Please read a copy of this book, as it contains all the details of the business plan and the DH-1 reusable launch vehicle. This is the baseline for my analysis, and I hope to fill in more of the engineering details as I go to confirm the viability of this design.

The details of the book are below:

The Rocket Company (Library of Flight Series)
Author: Patrick J.G Stiennon
1563476967 978-1563476969


This blog is the first step in achieving my goals.

There are three aims for this blog:
  1. Contact other people with a vision to build low cost reusable rockets
  2. Share information about low cost reusable rockets and the business methods behind them
  3. Provide a platform for charting my progress
I am a 32 year old Aerospace Engineer who works as a software developer. I believe that there is a revolution occurring in the space industry, as the transition from government development to private development occurs. This transition has many exciting opportunities that I want to be part of.

Therefore I have opened this blog as the first tangible step in this process. Please contact me if you wish to share ideas, thoughts, or information.