Meet Saturn V's successor – the Space Launch System
Sen—When it comes to rockets, bigger is better. The farther you want to travel into space, or the more you want to put there, the more powerful the engine you need, the more fuel you need to power it and bigger the rocket you need to build to house everything.
The last time mankind ventured any further than low-earth orbit was during the Apollo era and it’s no coincidence that the rocket that lofted those Apollo astronauts into space, the mighty Saturn V, is still the largest and most powerful rocket ever built.
Now, after more than three decades of operating what amounts to a low-Earth orbit taxi service, NASA has its sights set once again on deep space—and, this time, the Moon will be one of the less ambitious targets.
After revisiting the Moon and capturing a near-Earth asteroid (yes, they really have plans to do this), NASA has ambitions to send astronauts to Mars by 2031—to achieve all this, they are building a new rocket, the largest and most powerful ever built.
In its ultimate ‘Block II’ crew-carrying configuration, the rather prosaically named ‘Space Launch System’, or SLS, will stand seven metres taller than the 110-metre-tall Saturn V; will generate 20 per cent more thrust; and will be capable of lofting 130 metric tons of cargo into the heavens. Even in its initial 70-metric-ton ‘Block I’ form, the SLS will stand 98 metres tall and will generate ten per cent more thrust than Saturn V.
Having abandoned the ‘reusable’ ethos of the ambitious, but flawed Space Shuttle system, SLS harks back to the multistage crew launchers of the Apollo and pre-Apollo era—although some of its components, such as the main engines and solid rocket boosters (SRBs), have been borrowed from the Space Shuttle.
Main thrust will be provided by the vehicle’s ‘core stage’. This will be common throughout the SLS’s evolution and will house four Shuttle-derived, liquid hydrogen/liquid oxygen-fueled, RS-25 engines. The main engine’s thrust will be augmented by two Shuttle-derived SRBs, which have been upgraded from four segments to five but will no longer be recoverable. Instead, they will sink to the bottom of the Atlantic. NASA will eventually move away from the Shuttle’s SRBs and develop new solid/liquid-fueled boosters.
When the SRBs and core stage have dropped away, the SLS’s upper stage takes over. In its ‘Block I’ guise, thrust will come from NASA’s venerable RL-10 engine, which has been in service since the 1960s and is still employed to power the upper stages of United Launch Alliance's Atlas V and Delta IV rockets. This will be uprated to an upper stage made up of four RL-10 units—original designs included NASA’s new J-2X engine, which was developed for the cancelled Constellation programme’s Ares launcher, but this was mothballed by the agency.
To allow the ‘Block II’ SLS to carry 130 metric ton payloads, the Upper Stage will receive a more powerful, as yet unspecified, upgrade in around 2030.
When it’s not hauling cargo, the SLS’s crew components, the Orion Multi-Purpose Crew Vehicle (MPCV), will sit atop the upper stage.
The MPCV spacecraft is based on the Orion Crew Exploration Vehicle from the cancelled Constellation programme and will carry a crew of four astronauts beyond low-Earth orbit for exploration of the Moon, asteroids and Mars. It will consist of two main modules—the Orion command module and the Orion service module.
Derived from the European Space Agency’s Automated Transfer Vehicle (ATV), the Orion service module, provides maneuvering thrust to the MPCV and environmental support to the crew module.
The crew module, despite looking like it was dug up from the Apollo programme’s parts bin, is claimed by NASA to be one of the most technically advanced spacecraft ever built. It will transport four astronauts on deep-space assignments and then carry them back to Earth – protecting them from the rigors of reentry with the largest heat shield ever built.
NASA are hoping to get SLS test flights off the ground in 2018 and launch the first manned missions in 2020/2021.
Whilst NASA continues to build its new rocket, its worth noting that not everyone agrees that SLS is the way to go in light of progress being made by private space. For example, SpaceX—which has had success with its Falcon 9 rocket used to launch its Dragon cargo ship to the space station— expects to start testing its new heavy-launch vehicle, the Falcon Heavy, as soon as 2015 and, while it won’t have the raw lifting grunt of the SLS, it will still be able to carry more than 50 metric tons of payload into low-Earth orbit and it could potentially do so at less cost to NASA. Its too early to say whether such considerations will have any impact on NASA's plans for SLS.