Rocket boffinry in pictures: Gulp the Devil's venom and light a match
How scientists sup from Wernher von Braun's cup
Feature It's been more than 70 years since the first successful test flight of the German Vergeltungswaffe 2 (V2) - the weapon that paved the way for subsequent rocket-based efforts to escape Earth's surly bonds.
On 3 October 1942, a team headed by Wernher von Braun watched its creation rise from the launchpad at Peenemünde, little suspecting that within three years it would conduct similar test flights for the benefit of the United States.
Wernher von Braun at Peenemünde in 1942, and in his office in the US
Von Braun's work on the V2 was vital to America's space ambitions, and he successfully guided the country towards the mighty Saturn V, which lifted Apollo missions to the Moon.
In the 43 years since Neil Armstrong planted his boots on the lunar surface, we've honed the art of the rocket launch, enabling us to establish bases in Earth orbit, send probes to distant worlds and ring our planet with satellites and telescopes giving a tantalising glimpse into the vast universe beyond our tiny blue marble.
However, all of these achievements are underpinned by technology that hasn't changed much since the V2, for all the advances in fuels, materials and electronics.
Spot the difference: V2 and Soyuz launches
The V2 was powered by a liquid ethanol/water mix and liquid oxygen (LOX). The Russian workhorse Soyuz has, since the 1960s, been lifting payloads with a blend of LOX and kerosene. In both cases, the initial propellant/oxidant mass constitutes a large percentage of the total vehicle mass, and this seriously limits the rockets' ability to lift large loads.
The use of solid rocket boosters (SRBs) can provide extra oomph, as shown in the US's space shuttle programme, although this "light the blue touch paper and stand well back" approach has its risks.
Whether a rocket is powered by liquid or solid propellant - or a combination of both - the quantities of potentially explosive material required just to get off the ground makes vehicles prone to spectacular - and sometimes tragic - failure. The 1986 Challenger disaster was caused by a seal failure in one of the orbiter's SRBs, which in turn ruptured the external liquid hydrogen fuel tank, resulting in a catastrophic explosion.
Nonetheless, space agencies worldwide continue to put their faith in rockets, in the absence of a workable alternative. In the next part of our series, we'll look at some theoretical technologies which may one day render the grandchildren of the V2 obsolete. First, here's a quick overview of various current international capabilities.
In 2003, the communist state put itself on the orbital map with its Shenzhou 5 mission, becoming the third nation to develop an independent manned-spaceflight capability.
"Taikonaut" Yang Liwei was lifted aloft by a Long March 2F rocket burning the hypergolic melange of dinitrogen tetroxide (N2O4 - aka nitrogen tetroxide, or "NTO") and unsymmetrical dimethylhydrazine (UDMH) in four main engines and four strap-on boosters. The final stage packed a single N2O4/UDMH unit.
A Long March 2F lifts Shenzhou 5 at Jiuquan Satellite Launch Centre in 2003
Development of the Long March series began back in the 1960s, based on the country's intermediate-range ballistic missile (IRBM) and intercontinental ballistic missile (ICBM) programmes.
The Long March 3 and 4 series - mostly rolled out for satellite launches - also use N2O4/UDMH motors, although the final stage of the 3 variant is reportedly a liquid hydrogen (LH2) and LOX powerplant.
The Long March 5, 6 and 7, currently in development, will switch to LOX and kerosene for the main stages, sticking with LH2/LOX for the final stage. Exact details are not forthcoming, since the Chinese National Space Administration is remaining tight-lipped on its capabilities.
Hypergolic rocket fuels work on the spontaneous combustion on contact between propellants, such as N2O4 and forms of hydrazine (N2H4). The engine of Germany's Messerschmitt Me 163 brought together a mix of 80 per cent concentrated hydrogen peroxide and 20 per cent oxyquinoline (T-Stoff) with methanol blended with hydrazine hydrate (C-Stoff) to provoke the required reaction.
Such fuels have a reputation for toxicity and instability. Soviet scientists honoured nitric acid plus hydrazine with the name "Devil's venom" for its corrosive and poisonous properties.
Although stable, Devil's venom claimed the lives of 92 people in October 1960 at Baikonur test range, when the second-stage engine of a prototype R-16 rocket fired on the launchpad, provoking a massive explosion. The event is the worst disaster in the history of rocketry.
The European Space Agency's (ESA) Ariane 5 has a heavyweight reputation in the commercial launch sector, and its 2011 lift of the 20.06-tonne Automated Transfer Vehicle (ATV) Johannes Kepler - carrying supplies to the International Space Station - showed it has the clout to mix it with the big boys.
The heavy-lift Ariane 5 ECA
Ariane was spawned in a 1973 agreement between France, Germany and Britain. While the the 1-4 models evolved from ICBM technology, the 5 series represented a virtually complete redesign intended for tasks such as carrying the proposed Hermes spacecraft into orbit. The Evolution Cryotechnique type A (ECA) variant, seen above, is a satellite-lifting workhorse capable of hefting 10 tonnes, while the more powerful ES (Evolution Storable) model is responsible for ATV duty.
Since 1996, the Ariane 5 has performed 68 launches, with four failures. It relies on LH2/LOX for single main and second-stage engines, backed by two SRBs.
These boosters are - in common with those from the space shuttle programme and small motors regularly used by amateur rocketeers - packed with ammonium perchlorate composite propellant (APCP).
This is a solid mass of oxidising ammonium perchlorate and aluminium powder, held in a binder - commonly hydroxyl-terminated polybutadiene (HTPB), which is also a fuel in its own right for some hybrid rockets.
In the case of the Ariane 5, the boosters provide 92 per cent of thrust at lift-off, with each burning 138 tonnes of APCP until separation at an altitude of about 60km.
SRBs provide plenty of bangs per buck, although their obvious disadvantage is they can't be turned off once you hit the igniter button.
APCP will continue to give the Ariane 5 a leg-up for the foreseeable future. The ESA hopes to have an "ES Galileo" version of the rocket ready by 2014, able to put four Galileo global navigation system satellites into orbit in one hit.
Since its establishment in 1969, the Indian Space Research Organisation (ISRO) has overseen the subcontinent's advance from its first satellite - 1975's Soviet-launched Aryabhata - to the 2008 Chandrayaan-1 lunar orbiter and impactor mission.
Chandrayaan-1 was launched atop a Polar Satellite Launch Vehicle (PSLV), and the ISRO website offers overviews of this and the country's other operational lifter: the Geosynchronous Satellite Launch Vehicle (GSLV).
India's Geostationary Satellite Launch Vehicle (GSLV) blasts off from Satish Dawan Space Center at Sriharikota in September 2004
The PSLV's range of thruster types is interesting. The first stage boasts "one of the largest solid propellant boosters in the world", tipping the scales at 139 tonnes of fuel. It's assisted by six strap-on solid propellant motors, four fired on launch and two in the air.
The second stage "Vikas" engine is a N2O4/UDMH unit, while the third is once again fuelled by solid propellant. The fourth stage has two engines fuelled by the hypergolic reaction between monomethylhydrazine (MMH) and nitrogen oxides.
The three-stage GSLV has the same solid propellant first stage as the PSLV, but with four Vikas engine boosters strapped on. The second stage is propelled by a single Vikas engine, and the third has a liquid hydrogen/LOX motor.
The ISRO is currently developing the Geosynchronous Satellite Launch Vehicle Mark-III (GSLV III), with two solid boosters, a liquid-fuelled second stage and a final LH2/LOX push capable of putting satellites weighing anywhere between 4,500kg and 5,000kg into orbit.
In 2007, the country announced it will put a pair of astronauts into a seven-day low-Earth orbit in 2016, thereby becoming the fourth nation in the extra-atmospheric manned mission club.
Japan's first forays into space - such as its first satellite Ohsumi, launched in 1970 - relied on purely solid rocket motor technology.
However, as the Hayabusa probe blasted off en route to the Itokawa asteroid in 2003, propelled by a M-V solid-fuel rocket, the country was struggling to get its HII liquid-fuelled programme off the ground.
The National Space Development Agency of Japan (absorbed into the newly formed Japan Aerospace Exploration Agency - JAXA - in 2003) suffered two early failures of the LH2/LOX rocket, and it wasn't until 2005 that a HIIA model enjoyed its first successful flight.
In its standard configuration, the HIIA's single main engine is augmented by two "polybutadiene composite solid propellant boosters", lifting the second stage and its LH2</LOX engine heavenwards.
JAXA's H-II B on the launch pad in July 2012
The mightier HIIB has two first-stage liquid motors, plus four solid boosters, and a LH2/LOX second stage.
According to JAXA, the HIIB's two primary roles are HTV operations and multiple satellite launches. The HIIA is also capable of lifting multiple kit, as it showed back in January when it deployed two satellites, including the Information Gathering Satellite (IGS), designed to warn of hostile missile activity.
With its tried-and-trusted Soyuz system, Russia is currently the only nation able to deliver astronauts or cosmonauts to the International Space Station (ISS). The venerable Soyuz lifter dates back to 1966, a development of the Vostok rocket family, which in turn evolved from the world's first ICBM - the R-7 Semyorka.
Soyuz TMA-5 spacecraft blasts off from Baikonur Cosmodrome in Kazakhstan on October 14, 2004, carrying astronauts to the space station
With over 1,700 lift-offs under their belt, the Soyuz's kerosene/LOX engines have proved a reliable and economic means of getting off the ground. The vehicle has six motors, one for each of the second and third stages, with four bolted to the second-stage core in their familiar conical housings. The Soyuz-2 variant has an optional N2O4/UDMH third stage, allowing it to launch satellites into higher orbits.
Soyuz's long career has not been without its low points. In August 2011, an unmanned Progress vehicle was lost after a rocket malfunction delivered it to Siberia rather than the ISS. In January this year, mindful of Soyuz's creaking bones, the Russian Space Agency (Roscosmos) announced it would spend £43bn on an "energy transportation module with a promising propulsion installation that will be ready for testing by 2018".
In the meantime, Soyuz will slog on, as will the long-serving Proton heavy lifter, which mostly earns its keep as a commercial satellite transport.
A proton carries the DIRECTV 12 satellite aloft in 2009
The Proton's maiden flight was in 1965, after the Soviet Union scrapped its initial plan to use the design and its N2O4/UDMH powerplants as a "super ICBM".
No less than ten hypergolic motors - six in the first stage, three in the second and one in the third - give the current Proton M variant the capability to lift 22 tonnes to low Earth orbit, or 3.2 tonnes into geostationary orbit.
The Proton is slated to be replaced by the Angara 5 rocket - part of a family of various lifting capacities built on a kerosene/LOX-powered "Universal Rocket Module" concept, where more modules bolted to a common core provide more lift. The second stage will carry either a kerosene/LOX motor, or the Proton's N2O4/UDMH engine.
Over the past couple of years, there's been less talk about what the United States can do in terms of rocket lifting, and more focus on what it can't do.
Following the retirement of the space shuttle, America no longer has the capability to put people into space, and relies on the Russian Soyuz to do the job.
While it works on a homebuilt alternative, though, it's business as usual for the US tech sector charged with aerospace grunt work. The Atlas V has been a quiet success story since its first flight in 2002, suffering just one anomaly (early shut-off of its Centaur upper stage motor) in 37 missions.
A United Launch Alliance Atlas V rocket prepared for launch in 2002
The Atlas V is built around a "standard common core booster", around which up to five SRBs can be bolted according to requirements. The core comprises a Russian-built RD-180 keresone/LOX engine and Centaur second stage.
The Centaur commonly packs a single LH2/LOX motor, although two is an option if required. The 552 configuration (5.4m wide payload fairing, five SRBs and two Centaur engines) has the power to raise 20,520kg into low Earth orbit.
Plans are afoot to bring the Atlas V up to NASA "human-rating" standards. Boeing is eyeing the rocket as a lifter for its CST-100 (Crew Space Transportation) capsule, for private space flights and trips to the International Space Station.
Snapping at Boeing's heels in the race to get astronauts back into orbit on US-built kit is SpaceX, whose Falcon 9 has made headlines of late by successfully launching its unmanned Dragon capsules to the ISS, and successfully returning them to Earth.
Falcon 9 lift-off from Cape Canaveral, Florida
The Falcon 9's power comes from nine kerosene/LOX "Merlin" engines in its first stage, and a single Merlin in its second. Since the second stage is simply a scaled-down version of the first, with both sharing common components, SpaceX reckons the resulting construction savings are reflected in the rocket's "lowest cost per kilogram to orbit". For those considering sending something aloft, the company offers fixed-price launches for a modest $54m.
Drink the Devil's venom? No thanks...
This quick trip around the world of big-lift rocketry indicates we shouldn't expect any ground-breaking advances in the near future, at least on the fuel front.
That SpaceX relies on a simple blend of kerosene/LOX is significant. It's tried-and-trusted stuff, used for years on Soyuz and Atlas, and now proposed for the Russia's Angara rocket family, which will replace the hypergolic-powered Proton.
Similarly, China looks set to make the switch from hypergolic juice to kerosene/LOX for future models in its Long March family, with LH2/LOX powering the final stage, in common with the Atlas V's Centaur.
Accordingly, liquid hydrogen/oxygen mixes have a assured place on the launch pad - albeit with the problems associated with cryogenic fuels. SRBs, meanwhile, will continue to be the low-cost powerhouse of choice for going that extra mile.
In the end, though, for all the advances in design, composite materials, and control and computer systems, getting into orbit is still basically a matter of injecting a flammable substance and oxidiser into a combustion chamber and putting a match to it. In that sense, the Falcon 9 is simply a V2 with less sinister aims.
In the next part of this series, we'll investigate technologies offering an alternative to the rocket, and ponder whether we'll ever escape Wernher von Braun's long shadow. ®