The list of spacefaring nations remainssmall, but thanks to continuing advances in technology that promise to reducethe financial and logistical hurdles involved,the numbers are set to increase. One country that could be joining the club, ifthe University of Queensland (UQ) and Heliaq Advanced Engineering get their way, is Australia. The two are teaming up on a project intended to deliver payloadsweighing from 50 to 500 kg (110 to 1,102 lb) into orbit.
Called Spartan, the planned three-stage project is aimed at riding the surge of interest in the smallsatellite market. The first stage consists of a reusable rocket booster calledthe Austral Launch Vehicle (ALV). This would launch vertically carrying the upperstages of a rocket to scramjet take-over speed of Mach five before releasingthem at an altitude of around 25 km (15 mi).
The ALV would then deploy a swiveling,oblique wing and nose-mounted piston engine to return to base using wings andpropellers as the hydrogen-fueled second stage Spartan scramjet accelerates toMach 10, releasing the rocket-powered third and final stage at an altitude ofaround 40 km (25 mi) before it glides back to base for a conventional landing.
"This is aonce-in-a-generation opportunity for Australia’s hypersonic industry to jointhe space community," says Professor Michael Smart, the Chair ofHypersonic Propulsion at UQ's Centre for Hypersonics. "Currently, thereare about 1,265 satellites orbiting in space, but the cost to launch a singlesatellite is astronomical. "Our project aim is to reduce this cost and makeit more economically viable for smaller nations and organisations to launchtheir own satellites and monitor their own space activity through thedevelopment of a reusable space launch system."
The reusable ALV and Spartan scramjetstages would allow 95 percent of the system to be reusable, while reducing reliance on converted Russian missile launchers or hitching rides with larger satellites that are launchedinto much higher orbits. Satellites placed into orbit would be able to be monitored nationally orinternationally.
The project team is developing sub-scaleALV and Spartan technology demonstrators, and expects to fly an ALVdemonstrator (ALV-0) boasting a three-meter (9.8-ft) wingspan by the end ofthis year, which is intended to demonstrate systems deployment and low-speedhandling.
"It willtake off like a normal aircraft, stow the wings and then redeploy them,"says Professor Smart. "This test flight will focus on the slow speedhandling to prove that this prototype can actually work. We are trying toconcentrate on the new things, not the classic rocketry things that have beendone before."
The team will thenlook to follow up with a rocket-powered demonstrator (ALV-1), but this is stillin the funding stages. These initial phases are expected to be carried out asadvanced academic research projects aimed at reducing risk and provingfeasibility of the concept at a minimal cost. Subsequent phases, including thedeveloping and testing of an ALV-2 full envelope test vehicle and commercial operationof ALV-3 vehicle, are expected to be commercial endeavors.
Source: University ofQueensland, Heliaq Advanced Engineering
http://science.nasa.gov/science-news/science-at-nasa/2000/ast07sep_1/
The idea that a purely air-breathing propulsion system can be a more efficient and cheap way into orbit stumbles on the reality of thermodynamics. *Any* heat engine has a maximum efficiency, described by Carnot's equation. That is, ...The highest temperature in the engine minus the Lowest temperature in the engine, all divided by the Highest Temperature. (Units in degrees Kelvin)
The low temperature in an air-breathing reaction engine is the inlet temperature, while the high temperature is the exhaust temperature. That means that at near orbital velocity the *low* temperature is about 4-5,000ºK, while the high temperature must be above that. Too far above that, and all materials the engine could be made of melt or vaporize. This means that in the last 30% of its acceleration, as pure air-breather, it sinks below 30% efficiency, and gets worse the closer it gets to orbital speeds.
By contrast, most pure rockets are between 95% and 98% efficient throughout their flight. Thus, I am strongly skeptic of "efficiency" and low-cost in attempts to use the atmosphere as oxidizer.