Hydrogen & Oxygen Production & Liquification

This first stage of the ULSF project is the production and liquification of Hydrogen and Oxygen. The objective here is to estimate a first experiment.

The ULSF goal is to minimize capital intensity and maximize reproducibility for any effective degree of efficiency in establishing its technology kernel. Applying these principles to this area, we're looking for a low energy solution to the production and liquification of Hydrogen and Oxygen. Energy and material capital consumers of concern include pumping gas to high pressure, which would be avoided if possible.

Hydrogen and Oxygen production is planned with a Hoffman Apparatus powered Solar Photovoltaic Cells.

The general scheme is shown here. Gas O₂ and H₂ is produced on the left and collected in gas reservoir tanks for each liquifier. On the right is an air liquifier, which needs to supply liquid air to the H₂ and O₂ liquifiers.

From what I understand, a single column Joule Thomson cooler can liquify air. The critical parameter is the effect of the expansion of gas in the column, either heating or cooling. This is determined by pressure and temperature, and is detailed in "Joule Thomson Inversion Curves and Related Coefficients".

The interior of a liquifier is a set of heat exchangers.

In this diagram, the two column liquifier on the left is shown with a column for the working fluid on the right. Within the two column liquifier, the right hand column is cooled by an evaporating volume of the liquid working fluid. The left hand column is cooled by the expansion of gas from the bottom of the column. According to the temperature of the gas, some part will liquify in expansion.

The liquifier and gas must be cooled to a temperature under the inversion curve in order that the gas expansion is cooling. And in order to reach the temperatures required, the liquifier requires vacuum containment and radiative shielding.

The expansion valve is shown in the bottom of the left hand column. A "porous plug" is employed to serve a couple purposes. It maintains a pressure differential between the interior of the column and the interior of the heat exchange tubing within the column. And it serves to cause some period of time to accompany the expansion. This writer wonders whether an interesting course of experimentation would be to employ a capillary tube that could be measured and reproduced with particular precision.

Work to be done includes developing an understanding of "Curves and Coefficients", grasping the temperature- pressure relation, and an experimental definition of pressures within the components.

Thanks to the Space Tweep Society for supporting this work

A cryogenic H2+O2 technology set

The objective of this white paper is to outline a technology set for basic capabilities in open source space flight engineering.

Composite materials and cryogenic H2+O2 propulsion make possible an ultra light economy of scale for performing work in space including the deborbiting of space debris, the videography of space events, and the flight and return of experiments in systems and materials.

In traditional, large scale space flight systems, there exists an economy of scale in the large, where the marginal cost of additional mass to orbit is decreasing. This fact made possible the Apollo missions in the Saturn V, and promotes the efficacy of Heavy Lift Vehicles today.

At the opposite end of the spectrum is another kind of economy in the small scale. Very light weight, robotic space flight vehicles are practical via current technology and modest budgets for small groups of engineering hobbyists and small technology businesses.

As open source engineering has done for software on the internet, the internet itself, the world wide web and for millions of web sites and desktops around the world, open source engineering can do for space flight today.

Kernels of technology for independent development can bridge the gap between the blank page and effective known solutions.

Composite materials and cryogenic H2+O2 propulsion can achieve these goals.

As one of the first of its kind, the project is an end to end space flight program in the large number of steps required to develop and demonstrate the various technologies required to perform space flight, videography, and then the disposal of space debris.

The ultra light space flight objective requires only a basic and effective level of efficiency, as subsequent work across the internet may refine and enhance these initial products.

• First, there is the production, liquification and storage of Hydrogen and Oxygen.
  Current planning includes solar photovoltaic O2 and H2 production, a two column Joule-Thomson liquifier in an air, hydrogen and oxygen cascade, and a single column storage system.


• Second, is the development of a very small (1 to 15 N) cryogenic propulsion system with very fine flow control (1 to 4 grams per second).


• Third is the development of a hover test vehicle. Current planning is for a roughly 25 centimeter diameter model employing one main 14N engine and three 1N attitude control engines in H2+O2. The object is to hover above ground effect altitude for roughly thirty seconds, ascending and descending as slowly and as smoothly as possible, to demonstrate control and function.

From this point, the remainder is relatively straight forward. The technology kernel will be complete and engineers across the internet may pick up the pieces for increasingly advanced developments, tests and flights. The possibilities are potentially endless and the internet community at large may develop them as desired.

The principle is to document research and development activity for the reproduction of results. The primary objective for open source engineering writers is sharing or comprehension, and secondarily precision in reproducibility -- communication is fundamental, and precise reproduction can be prohibitive to publication.

A tool set for collaborative, knowledge- based engineering is in design and may be developed.

Milestones

• Production and liquification of Hydrogen and Oxygen

  
  This stage is the construction of the fairly well known Joule-Thomson liquification cascade. Virtually any level of efficiency in production is adequate.



• Storage maintenance of cryogenic liquids

  
  This stage is optional, as it is redundant to the primary liquifier. A single column liquifier is interesting due to a substantial savings in the power requirements for long term storage of cryogenic liquids, and possibly for application to flight.



• Composite materials production and fabrication

  
  This stage is to identify or develop a carbon- phenolic resin for completely reproducible results. The resin embeds Carbon Tow for the fabrication of small integrated structures including tank, combustion chamber and fuselage members. Ideally, fuel and oxidizer lines and valve bodies are also constructed with similar techniques in the same material.
  
  A single material approach simplifies a number of systemic relations from the sharing of knowledge of the production of the material to the design and use of the material. A carbon- phenolic composite is expected to be capable of satisfying thermal, mechanical and mass properties across the primary structures in an ultra light robotic craft.
  
  Fabrication methods and tools are also products of this stage.



• 15N engine

  
  The larger engine will be easier to develop than the miniature engine required for attitude control. Regenerative cooling drives a fuel and oxidizer pump. A concentric injector is expected. Chamber shape may be a straight tube, hemispherical at the injector.



• 1N engine

  
  A very small engine with identical development and test requirements including sustained operation at full power.



• Integrated flight propulsion system

  
  This stage develops bench results into a flight unit, tightening the requirements on test articles into a final form.



• Integrated flight control system

  
  An objective flight control system integrates sensors and actuators with its programming. An objective is an altitude, attitude and time in a general frame of reference. When the whole craft is designed to simplistic robotic objectives, the flight control system is fairly simple.
  Actuators are solenoid needle valves acting against fluid and gas pressures.



• Hover flight

  
  The flight has two objectives, flying altitude and landing altitude.



• Construction

  
  The envisioned technology set is planned as one primary material employed with one primary construction technique: carbon tow embedded in a carbon- phenolic resin.
  
  This material will be applied to tanks, engines and fuselage; perhaps even to lines and valves. Valves are envisioned as solenoids in a needle configuration. Lines and valves will be sized to the required power range.
  
  If fabrication techniques and tolerances can support all components, then the integrated flight system will be far simpler to produce.
  
  Cryogenic interior and craft exterior surfaces will be skinned in mylar or aluminum foils to reflect radiated heat. Spaces between the fuselage outer walls and tank exteriors will be evacuated to a high vacuum to insulate the cryogenic system from conducted and convected heat. Craft interior structural ribs and spans will be minimized for conduction and mass.

General application safety for ultra light robotic systems design

The security principle for this novel domain in general application ultra light robotic systems follows from organic systems theory. When the whole robotic unit is not completely under control, it is completely dead.

For example in an ultra light propulsion system the dead unit principle translates into valves powered - closed, and dead - open (venting). A dead unit is relatively safe.

Thanks to Lucile Delheimer for work on editing this paper.

Thanks to the Space Tweep Society for general support in the production of this paper