Last week, SpaceX took the first step in its quest to build a reusable launch vehicle. The goal is to create a rocket that can autonomously return to the launch site and land vertically on dry ground. Refurbishing and reusing a rocket stage is much more cost efficient than rebuilding a new stage for each launch. The prototype vehicle that demonstrated the technology behind this idea is called Grasshopper, and it’s made its maiden voyage.
The 106 foot tall Grasshopper, so called because of its spindly insect-like legs, is a vertical takeoff and landing test vehicle (VTVL). It’s made of a modified Falcon 9 first stage with a Merlin 1D engine. The Merlin 1D, which burns kerosene and liquid oxygen and can generate up to 147,000 pounds of thrust, is an upgraded version of the Merlin 1C that generate 78,000 pounds of thrust at sea level.
Last Friday’s test (September 21) was a successful demonstration flight SpaceX’s test facility in McGregor, Texas. But it wasn’t exactly a simulated landing from stage cutoff after launch. It was a small hop. The vehicle rose just six feet off the ground before landing gently on its legs. Still, it’s a step in the right direction and a critical milestone in the quest to develop a fully reusable booster system. Having a reusable first stage will also complement the reusable Dragon capsule spacecraft, ultimately making the whole SpaceX system more cost effective.
SpaceX plans to follow last week’s short hop with more small hops in the coming months. The next tests will be conservative, though larger than the six foot hop. The first tests will reach between 200 and 240 feet and last less than 1 minute. From there, Grasshopper’s flights will get progressively more daring. The vehicle will get as high as 1,000 feet. At that height, it will demonstrate its ability to hover before making a soft landing. Later tests will likely see the Grasshopper climb as high as 11,500 feet on a 160 second flight before making the same smooth vertical landing.
Meanwhile, SpaceX is continues to work on qualifying the Merlin 1D engine for flight. Right now, full-duration firing tests are pending and currently scheduled for November. If these tests are successful, the Merlin 1D will power a Falcon 9 into orbit in March or April 2013.
The only rocket stages that have been successfully recovered and reused after launch were the space shuttle’s solid rocket boosters (SRBs). These two stages on either side of the main fuel tank provided more than 80 percent of the thrust needed to kick the space shuttle into orbit. They fell away two minutes after launch once their fuel was exhausted and splashed down in the ocean. The casings were successfully reused on subsequent missions to cut overall program costs.
If SpaceX does manage to turn the Grasshopper into a fully autonomous vertical landing rocket stage, this, combined with the reusable Dragon capsule, could see a major change in the landscape of spaceflight. Cheaper missions could mean more launches.