The market for smaller satellites grows strongly, the quest for low cost launches for satellites at the smaller end of the spectrum has led to various concepts to be considered – as least some of which may come to fruition. On the one hand, dedicated multi-stage expendable rockets always seemed expensive, sharing launches is famously be troublesome, and yet, when it comes to reusability the relatively low flight rates currently flown do not justify it.
Perhaps the biggest question is about launch price and how low can you go with current rocket technology. The US firm, Microcosm, seems to have the answer with their Scorpius rocket series. At the Reinventing Space Conference (RI Space) held at the Royal Society in London in November, Jim Wertz explained that Microcosm’s technology tweaks in combination with deliberately aiming to optimise for cost rather than outright performance was the key to having a cheap to operate expendable launch system.
These included LOx/kerosene pressure fed rocket engines and an advanced “High Performance Pressurisation System” (avoiding the need for expensive-to-manufacture turbopumps), using ablatively cooled combustion chamber and composite nozzle technology (avoiding the need for expensively braised pipework for regenerative cooling), and composite fuel tanks (cutting the rocket empty weight to give the relatively poor performing rocket a payload boost), and finally, making the rocket family very modular, to allow the same rocket stages to be used on several different vehicles (a high enough number of stages to allow the cost benefits of assembly line manufacture). Wertz noted that a key technology, and one that the recently cancelled US Army SWORDS low cost launch vehicle stumbled over, was the manufacture of the composite tanks which would have to cope with cryogenic temperatures of -196 degrees Celcius. The rocket stages would all employ gimbal steering for its 7,000lb thrust engines which Jim Wertz noted would give the launch vehicles “an absurd amount of control authority.”
So how close is Microcosm to launching an orbital launch vehicle? Having already flown two suborbital test rockets as technology test vehicles, Wertz remarked that the first orbital flight of the smallest version of the Scorpius family, the “Demi-Sprite” which would have a payload of 160kg to LEO for a price of just US$3.6 million , would occur “in 30 months’ time”. This rocket would, in turn, lead to the full Sprite rocket which would have a payload of 480kg to LEO (300kg to Sun-synchronous orbit) for a launch price of under US$6 million. Later rockets in the family would have payloads above 2,000kg.
While “air breathing” rocket and reusable technology is planned for large launch reusable launch vehicles such as Reaction Engines’ Skylon design, using it for smaller launch vehicles is thought by many to be impractical.
Adrian Schutte’s team of part time scientists and students of Heliaq Advanced Engineering based in South Africa, have been working on a demonstrator to show how practical it would be to operate fly-back reusable boosters as a first stage for a three-stage satellite launcher design, called Austral. The solid rocket powered test booster will have a slew deployment wing, butterfly tail and a foldable propeller. While that device is not intended to reach high Mach numbers, later versions should reach Mach 5 during launch before separating and decelerating to the subsonic regime for a straight wing flown recovery.
The firm has now teamed up with the University of Queensland for possible use of a scramjet (Supersonic Combustion Ramjet) to act as the Mach 4 to Mach 12 second stage. Dawid Preller of the University of Queensland reported present test plans in the Hifire programme including a Mach 7 flight of HiFire 8 in 2017. Preller added that using a Scramjet 2nd stage as part of the Austral with a conventional rocket final stage would allow the injection of a 500kg payload to a Sun-Synchronous Orbit. Launches would take place from Cape York in Australia.
While there were other contenders presented at RI Space most noticeably the Rocketplane XS-1 first stage rocketplane concept, and the Nammo North Star three-stage hybrid rocket, the real spectre at the feast in the way of developing a dedicated low cost launch competitor are shared or piggy back launches on current launch vehicles.
Gerry Webb of the satellite launch arranger, Commercial Space Technologies (CST), explained that piggy back and shared launches remain, in effect, be the main competitor to dedicated launchers with their very low prices (US$6 million for a 200kg to a Sun-synchronous low Earth orbit) being similar to those being mooted for future light launch vehicles. Nevertheless, Gerry Webb said shared and piggyback arrangements did have downsides including the difficulty in coordination, not being able to fly to exactly the orbit you want, and being treated as second class payloads including sometimes being delayed by the main launch payload. This happened to the UK’s UKube 1 and Techdemosat with their launch being delayed by nearly two years.
Gerry Webb also noted that some of the former missiles currently being used as launch vehicles, Rockot, Dnepr, Strela, would soon be coming to an end as these missiles are becoming time expired with little support from the Russian military. Webb noted that they might be able to carry on to 2020 but that 2017 was a more realistic date. CST still has very strong connections with the Russian launch authorities including Roscosmos and Rosboronexport. As such, CST still expects to continue to be able to offer piggyback or shared launches on those Russian and Ukranian rockets still operating including Soyuz, Tsyklon 4 (Cyclone 4) and hopes to offer launches on the smaller versions of Angara. Of course, Webb explained that CST would like to be able to broker launches on any new Western launch vehicles that arrive on the scene as well.
Note: The author is a small shareholder in Reaction Engines Limited. Seradata cooperates with CST on consultancy and data.
