Small hydrogen/oxygen rocket flowfield behavior from heat flux measurements

The mixing and heat transfer phenomena in small rocket flow fields with fuel film cooling is not well understood. An instrumented, water-cooled chamber with a gaseous hydrogen/gaseous oxygen injector was used to gather steady-state inner and outer wall temperature profiles. The chamber was tested at 414 kPa (60 psia) chamber pressure, from mixture ratios of 3.41 to 8.36. Sixty percent of the fuel was used for film cooling. These temperature profiles were used as boundary conditions in a finite element analysis program, MSC/NASTRAN, to calculate the local radial and axial heat fluxes in the chamber wall. The normal heat fluxes were then calculated and used as a diagnostic of the rocket's flow field behavior. The normal heat fluxes determined were on the order of 1.0 to 3.0 MW/meters squared (0.6 to 1.8 Btu/sec-inches squared). In the cases where mixture ratio was 5 or above, there was a sharp local heat flux maximum in the barrel section of the chamber. This local maximum seems to indicate a reduction or breakdown of the fuel film cooling layer, possibly due to increased mixing in the shear layer between the film and core flows. However, the flow was thought to be completely laminar, as the throat Reynolds numbers were below 50,000 for all the cases. The increased mixing in the shear layer in the higher mixture ratio cases appeared not to be due to the transition of the flow from laminar to turbulent, but rather due to increased reactions between the hydrogen film and oxidizer-rich core flows

Weight savings in aerospace vehicles through propellant scavenging

Vehicle payload benefits of scavenging hydrogen and oxygen propellants are addressed. The approach used is to select a vehicle and a mission and then select a scavenging system for detailed weight analysis. The Shuttle 2 vehicle on a Space Station rendezvous mission was chosen for study. The propellant scavenging system scavenges liquid hydrogen and liquid oxygen from the launch propulsion tankage during orbital maneuvers and stores them in well insulated liquid accumulators for use in a cryogenic auxiliary propulsion system. The fraction of auxiliary propulsion propellant which may be scavenged for propulsive purposes is estimated to be 45.1 percent. The auxiliary propulsion subsystem dry mass, including the proposed scavenging system, an additional 20 percent for secondary structure, an additional 5 percent for electrical service, a 10 percent weight growth margin, and 15.4 percent propellant reserves and residuals is estimated to be 6331 kg. This study shows that the fraction of the on-orbit vehicle mass required by the auxiliary propulsion system of this Shuttle 2 vehicle using this technology is estimated to be 12.0 percent compared to 19.9 percent for a vehicle with an earth-storable bipropellant system. This results in a vehicle with the capability of delivering an additional 7820 kg to the Space Station

Advanced APS Impacts on Vehicle Payloads

Advanced auxiliary propulsion system (APS) technology has the potential to both, increase the payload capability of earth-to-orbit (ETO) vehicles by reducing APS propellant mass, and simplify ground operations and logistics by reducing the number of fluids on the vehicle and eliminating toxic, corrosive propellants. The impact of integrated cryogenic APS on vehicle payloads is addressed. In this system, launch propulsion system residuals are scavenged from integral launch propulsion tanks for use in the APS. Sufficient propellant is preloaded into the APS to return to earth with margin and noncomplete scavenging assumed. No propellant conditioning is required by the APS, but ambient heat soak is accommodated. High temperature rocket materials enable the use of the unconditioned hydrogen/oxygen in the APS and are estimated to give APS rockets specific impulse of up to about 444 sec. The payload benefits are quantified and compared with an uprated monomethyl hydrazine/nitrogen tetroxide system in a conservative fashion, by assuming a 25.5 percent weight growth for the hydrogen/oxygen system and a 0 percent weight growth for the uprated system. The combination and scavenging and high performance gives payload impacts which are highly mission specific. A payload benefit of 861 kg (1898 lbm) was estimated for a Space Station Freedom rendezvous mission and 2099 kg (4626 lbm) for a sortie mission, with payload impacts varying with the amount of launch propulsion residual propellants. Missions without liquid propellant scavenging were estimated to have payload penalties, however, operational benefits were still possible

Hydrogen/oxygen auxiliary propulsion technology

A survey is provided of hydrogen/oxygen (H/O) auxiliary propulsion system (APS) concepts and low thrust H/O rocket technology. A review of H/O APS studies performed for the Space Shuttle, Space Tug, Space Station Freedom, and Advanced Manned Launch System programs is given. The survey also includes a review of low thrust H/O rocket technology programs, covering liquid H/O and gaseous H/O thrusters, ranging from 6600 N (1500 lbf) to 440 mN (0.1 lbf) thrust. Ignition concepts for H/O thrusters and high temperature, oxidation resistant chamber materials are also reviewed

Storm-water management in low-income countries

Rapid urbanisation coupled with a changing climate is increasing surface run-off in many cities in low-income countries. Badly managed run-off has a disproportionate impact on the poor. In a series of ten research projects the state of storm-water management in Vietnam, Nigeria, Uganda, Kenya, Pakistan and India has been examined, including issues of management, maintenance, health impacts (such as malaria) and design standards. The findings show that institutional issues such as urban planning, financing, management responsibility and skills levels are areas that require attention if storm-water is to be controlled effectively. Integrated approaches are required, making institutional coordination critical. Technical issues also need to be addressed, with silt and solid waste being a significant design problem

Surface water in temporary humanitarian settlements

In the Humanitarian Innovation Fund Gap Analysis for water, sanitation and hygiene issues (Bastable and Russell 2013), field staff identified environmental management of surface water as an area of concern, although this was not reflected at a head office level. This difference of perspectives could be an under reporting of this aspect of environmental sanitation to the global humanitarian community or a failure of experts to communicate the required response to surface water management in camps for displaced people. Reviewing core humanitarian engineering texts and global standards, this paper sets out the current state of the art and shows that there is a lack of clarity in the “ownership” of the problem and the established responses are disjointed and poorly articulated, especially at field staff level. Since the core texts have been written, there has been a change in the way surface water is being managed in urban areas. Sustainable urban drainage practices may have potential in resource poor but densely populated situations such as some refugee camps. The paper highlights the lack of adequate advice in both content and delivery mechanisms. More gaps and challenges were identified than solutions, but this is research narrowed down the gaps identified in 2013 to more specific issues, which is a step further to solving the problem

Exploring the capacity building ladder

Prompted by several visits providing support to universities in Africa, the author explores the challenges in delivering appropriate training to WASH professionals that is both accessible locally and sustainable in terms of time, finance, and human resources and physical facilities. The paper explores the two extreme scenarios of short-term local training courses and longer-term educational programmes in training centre or universities. As educational theory (pedagogy) has a jargon that may not be understood by the WASH sector, analogies are used to compare course design with the use of the "ladder" model, in particular the design of household and centralised water treatment systems and the challenge of moving from one model to another

Design of a digital signal processing system on chip for an eddy current probe

In 1965 Gordon Moore, co-founder of Intel, observed that the number of transistors per square inch on integrated circuits had doubled every year since the integrated circuit was invented. Moore predicted that this trend would continue for the foreseeable future. In subsequent years, the pace slowed down, but data density has doubled approximately every 18 months, which is the current definition of Moore\u27s Law. The Semiconductor Industry Association roadmap derived from Moore\u27s Law promotes continuation of the decrease in minimum feature size and wafer size increase as the bases for the semiconductor industry\u27s successful future. This continuation of the decrease in minimum feature size and increase in wafer size has a number of important implications. One such important implication is that there will be an increase in chip manufacturing cost. This increase in die manufacturing cost has caused chip designers to investigate the implementation of single chip systems instead of the traditional design of multiple chip systems. The benefit of having a single chip system is that it can provide the same performance yet consume less space and power than multiple chip systems, which in turn cut manufacturing cost. The research conducted describes the design and implementation of an integrated circuit digital signal processing system for an eddy current probe. For this project a digital signal processing system that removes noisy signal components and amplifies the signal produced by an eddy current probe was designed. The purpose of this system is to have the ability to detect cracks in a material and to output that information to an ADC, which then is used to provide digital information to a computer for interpolation. In order to create a digital signal processing system capable of this, multiple building blocks are needed. This includes the design of a low pass filter, a variable gain amplifier which incorporates an operational amplifier and digital-to-analog converter, a current bias cell, and a shift register. An analysis and discussion of the design and fabricated integrated circuit in a TSMC 0.18 micron process is presented

High-Performance Monopropellants and Catalysts Evaluated

The NASA Glenn Research Center is sponsoring efforts to develop advanced monopropellant technology. The focus has been on monopropellant formulations composed of an aqueous solution of hydroxylammonium nitrate (HAN) and a fuel component. HAN-based monopropellants do not have a toxic vapor and do not need the extraordinary procedures for storage, handling, and disposal required of hydrazine (N2H4). Generically, HAN-based monopropellants are denser and have lower freezing points than N2H4. The performance of HAN-based monopropellants depends on the selection of fuel, the HAN-to-fuel ratio, and the amount of water in the formulation. HAN-based monopropellants are not seen as a replacement for N2H4 per se, but rather as a propulsion option in their own right. For example, HAN-based monopropellants would prove beneficial to the orbit insertion of small, power-limited satellites because of this propellant's high performance (reduced system mass), high density (reduced system volume), and low freezing point (elimination of tank and line heaters). Under a Glenn-contracted effort, Aerojet Redmond Rocket Center conducted testing to provide the foundation for the development of monopropellant thrusters with an I(sub sp) goal of 250 sec. A modular, workhorse reactor (representative of a 1-lbf thruster) was used to evaluate HAN formulations with catalyst materials. Stoichiometric, oxygen-rich, and fuelrich formulations of HAN-methanol and HAN-tris(aminoethyl)amine trinitrate were tested to investigate the effects of stoichiometry on combustion behavior. Aerojet found that fuelrich formulations degrade the catalyst and reactor faster than oxygen-rich and stoichiometric formulations do. A HAN-methanol formulation with a theoretical Isp of 269 sec (designated HAN269MEO) was selected as the baseline. With a combustion efficiency of at least 93 percent demonstrated for HAN-based monopropellants, HAN269MEO will meet the I(sub sp) 250 sec goal