#### Oxygen Life Support Systems in a Spacecraft

##### Introduction

Looking into the very near future, tourists traveling into space no longer seems like some fantastic science fiction. The Blue Origin and the Mojave Aerospace Ventures companies are ready to operate their respective manned suborbital spacecrafts in the coming year[1]. While, The Boeing Company and the SpaceX are finishing the certification of their crewed spacecrafts to deliver people at the Low Earth Orbit. This is only the tip of the iceberg in the great competition.

The next ambitious goal of the space industry is to create space hotels (see Figure 1). For example, NASA already has announced opening the ISS for tourists. These objects are long term human habitations and as such have specific requirements for oxygen life support systems (OLSS). If these requirements are not met, people can die. Small variations in the chemical composition of a mixture of the gases all influenced by, pressure, temperature, a humidity and etc.[2]  can have disastrous effects. The work of some of these partial system can be analyzed and optimized using AxSTREAM NET™.

##### Types of life support system of a spacecrafts

The type and complexity of OLSS depends on the duration of the tourists staying in the artificial environment. For example, let’s consider the oxygen life support systems. A hypothetical manned spacecraft has an internal volume 15 m3 (530 ft3) and can carry six space tourists. The amount of the oxygen for the metabolism of one person is 0.830 kg/day[4] (Figure 2). The atmosphere should consists of 19.5 to 23.5 % of an oxygen[5]. Also, the amount of the reserve oxygen should be 0.035 kg (0.077 pounds) per human/hour. If our six space tourists start their journey with the environment gas in the craft at 23.5 % of the oxygen , it will take 3.5 hours to reach critical level. It’s enough time for a suborbital flight, and the oxygen life support system would only be needed as a reserve source. Read More

#### Unsteady Flow Simulation in Hydraulic Systems

An unsteady flow is one where the parameters change with respect to time. In general, any liquid flow is unsteady. But if a hydraulic system is working at constant boundary conditions, then the parameters of the fluid flow change slowly; thus this flow is considered steady. At the same time, if the parameters of the fluid flow oscillate over time relative to some constant value, then it called quasi-steady flow 1.

In practice, most fluid flows are steady or quasi-steady. Examples of the three flows are presented in Figure 1. Steady flow is presented by a simple pipe. The quasi-steady flow is represented by a sharpened edge channel. The unsteady flow is presented by an outflow from a reservoir.

##### Different Cases of Unsteady Flow

During operations, hydraulic systems act for long intervals at steady conditions which are called operating modes. Change between two different operating modes occurs over a short time interval (called a transient mode). If any hydraulic system works more than 95% of the time at these operating modes though, why is the unsteady flow is so important? Because the loads depend on time intervals. If the load is less, then the maximum system pressure is higher. Read More

#### Gas Turbine Lubrication Systems

Gas turbines have had a presence in many industries for more than a century. They are a unique technology for either producing an energy or propelling a vehicle and the efficiency of modern gas turbines is being improved continuously. One of them, a cooling system, has been described in earlier blogs. Another is the lubrication system of a gas turbine which we will cover in this blog. This  system, similar to that of a piston engine or a steam turbine, provides lubrication to decrease mechanical losses and prevent of wear on friction surfaces. Another function is the removal of heat released during friction by high rotational part and transmitted from the hot part of a turbine.  The basic units which need lubrication are the bearings supporting a shaft of a gas turbine 2.

##### Elements for lubrication

In a common case, gas turbine installation contains three main journal bearings used to support the gas turbine rotor 3. Additionally, thrust bearings are also maintained at the rotor-to-stator axial position 4. Click here for additional information about optimization of journal bearings. The bearing has important elements in its construction to prevent leakages from a lubrication system. The work, design and analysis of labyrinth seals is describe here.