Four Innovations That Will Make Space Travel Affordable
The Holy Grail of Space Technology is in Sight
Is a trip to space in your future? Space is only 250 miles away, but the cost of launching rockets has long been a barrier to space vacations. Expensive rockets are built and expended with each flight….imagine the ticket price of your last vacation if the plane you flew on was dumped into the ocean each way. With the recent advent of propulsive landing, Elon Musk’s Spacex and others are demonstrating that it is possible to partially reuse rockets. But if space is to be truly affordable, we need the holy grail…full and rapid reuse. This is precisely what Spacex Starship is hoping to achieve.
The key to achieving the “holy grail” of rocketry comes down to one word: efficiency. Traditionally, only 1% of the mass of a rocket was payload, with the remaining 99% of mass needed to propel it into space. This leave no extra mass margin for a return trip to Earth. Therefore, the less mass used to place a spacecraft into orbit, the more mass you can use for the equipment/fuel necessary to bring that rocket safety back to Earth. Here are four innovative ways engineers are tackling the efficiency problem.
Many rockets today use hydrogen fuel because it burns extremely efficiently. Rockets of the future, however, will use a less efficient fuel…methane. Odd choice right? Although it burns less efficiently, methane has other advantages over hydrogen. Methane is more energy dense than hydrogen, meaning smaller, lighter, and more compact fuel tanks. It also doesn’t require as much thermal management ( less insulation to keep it cold). Taken together, this makes methane the most efficient choice of fuel despite lower combustion efficiency.
Rockets try to minimize weight to maximize their efficiency, so building them out of heavy stainless steel would seem illogical compared to traditional materials like aluminum or super light carbon fiber. Stainless steel, like methane, hits a “sweet spot” that the “logical” material cannot match.
Steel is relatively cheap, easy to work with, and doesn’t corrode or rust easily. More importantly though, some kinds of stainless steel gain strength when cold. This works out perfectly. When the rocket is sitting on the launchpad it is under the greatest structural strain because it is fully fueled with cold propellant. That added strength allows for a thinner/lighter structure.
As an added bonus, however, stainless steel is also very heat resistant. When the first and the second stages are reentering the atmosphere at high speed on their return trip to Earth…they get very hot. Since steel can take most of the heat on its own, there is a greatly reduced need for heat shielding, saving an enormous amount of weight. This fact ultimately makes steel construction lighter than aluminum or other alternatives that would require heavy heat shielding.
New Control Surfaces
To reuse the upper stage of rockets, it is necessary to find a way of controlling the stages while they are reentering the atmosphere. Body flaps appear to be the way to go. Movable flaps can help guide the rocket toward the landing site. Body flaps also help spread reentry heating across a larger surface area, and reduce reentry speeds to limit maximum heating, easing the strain on the heat-shield and further reducing the need for heavy shielding.
New Sizes: Bigger is Better
Size isn’t strictly an innovation but that does not negate its importance. In rocketry, size matters. As a rocket grows larger, the available fuel (useful mass) grows faster than the surface area of the tanks needed to contain it (dead weight) in accordance with the square cube law of mathematics. In other words, larger rockets will have better fuel mass fractions that make them more efficient. This fact is not lost on the industry, as a number of massive rockets are in development.
With all of these amazing new innovations coming down the pipeline, the next decade of space exploration looks bright….and affordable. Entire new industries may open up, creating new and previously unforeseen sources of jobs and economic growth.
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