A Look at the Proposed Space Launch System

With the Constellation debacle seemingly behind us, NASA administrator Charlie Bolden proudly announced the successor to the Space Shuttle Program: the Space Launch System (SLS). Assuming that the SLS receives the proper funding, research and development (and that's a BIG assumption), what can we expect from this architecture?

The SLS is a shuttle-derived system. This means that the high-level configuration leverages the existing Shuttle tank and SRB, and thererefore launch infrastructures. This obviously speeds up development time and lowers overall programme cost, but most importantly it lowers risk.

To sum up, the SLS is basically a space shuttle minus the Orbiter (the white, airplane bit) and with the top part of a Saturn V bolted to the top. So you can see what NASA mean when they refer to "legacy architecture".

Lowering costs, risks, and development time is all well and good, but what capabilities will the SLS deliver? Will we still be stuck in the same Low Earth Orbit (LEO) that the Shuttle program doomed us to?

The SLS and MPCV infographic

The short answer is, "no". The SLS will be decidedly powerful enough to propel the MPCV (Multi Purpose Crew Vehicle) and the up to seven Astronauts inside it into "deep space". This opens up the option of manned missions to NEOs like comets and asteroids, or even to The Moon or Mars.



To achieve this, the SLS utilises SRBs for initial lift-off. These are identical to the Shuttle SRBs (the white boosters on the side of the orange tank) apart from that they have an extra segment, meaning longer burn time and heavier lift capability.

The External Tank (orange bit from the Space Shuttle) is equipped with LOX rocket motors,  slated to be the same as the RS-25 SSMEs from the Shuttle Orbiter. However, while the Shuttle used just three RS-25s, the SLS will be equipped with up to five.

Finally, the exciting part. The upper stage will utilise modified versions of the J-2 engines from the Saturn V moon rocket of the 1960s. The more modern version, the J-2X is slated to produce up to 1,300 KN of impulse for over 430 seconds, more than enough to top any feat accomplished in the 1960s!

The J-2 Engine from the London Science Museum

This summer I got to stand in front of one of the original J-2 engines at the London Science museum. As you can see, it is one mighty rocket motor. So it will be exciting to see what the J-2X is capable of.

NASA estimate a program development cost of ~$18 billion, including the MPCV. The sad thing is that the current plan is for the 70 metric-tonne to orbit capability, with full 130 tonne missions not to begin before 2030. Martian missions would need the latter, so don't expect to see american boot-prints on Mars before 2035. At best.

My personal opinion is a little pessimistic. Given the current commercial developments pioneered by SpaceX and Boeing, NASA could partner with Russia and invest those billions on a replacement for the ISS. That replacement, though, would not be a lab like its predecessor. It would have the dual purpose of being a construction site and a propellant depot. Here, astronauts would construct simple modular deep space vessels, fuel them, and launch interplanetary missions.

That may sound like science fiction, but the work but the International Space Station has given us more than enough data to make this a reality.