Big Dumb Boosters – The Low Tech Path to Orbit

By Earl Hunsinger

Would you spend five dollars on a single disposable paper cup? What if it was the lightest, best engineered cup in the world? How about if it was made out of exotic, imported paper? If something is made to be disposable, you expect it to be cheap. You expect the company that manufactures it to keep the cost down by using a simple design and inexpensive material. On the other hand, if you spend five dollars on a cup, you expect something that’s designed to be reused.

That same kind of common sense approach can be applied to the space industry. The guiding principle when building rockets has always been to reduce weight. After all, if you can reduce the weight of the rocket itself by a pound, you can carry a pound more of payload. However from a cost standpoint, this may not make as much sense as you would initially think. The boosters used in multi-stage rockets are built to be disposable, like our paper cup. Does it make sense to spend huge amounts of money on precision engineering and exotic materials for a rocket stage that is going to be used once and dumped into the ocean?

In the 1960s another school of thought was proposed, that of minimum cost design. In other words, instead of saying that money is no object when it comes to reducing weight, why not design a rocket that is cheaper to fly, even if it means sacrificing efficiency. This proposal was officially presented in a paper by A. Schnitt and Col FW Kniss in July of 1968. The paper was called "Proposed Minimum Cost Space Launch Vehicle System," but their concept came to be known as Big Dumb Boosters, or BDBs.

Basically the idea is the same as our disposable paper cup, since we are going to throw it away anyway, why not use the simplest and cheapest design and materials possible. In the case of a rocket, the initial suggestion was to use giant tanks made out of ordinary steel and filled with kerosene. These tanks would use gas pressure fuel feed systems instead of turbo pumps, which are more complicated and expensive. The simplicity of design is why these are called "dumb" boosters. Although kerosene, which would be burned with liquid oxygen or LOX, is not as efficient a propellant as other fuels, it is relatively cheap.

Would BDBs be a better way to reach orbit? Are they even feasible? The paper Big Dumb Boosters – Can we build them? presents some rough math that seems to prove their viability. In addition, 1997 and 1998, Arthur Schnitt wrote a series of columns on Minimum Cost Design spacecraft, or BDBs, which are available on Dunn Engineering’s website. These also show the benefits of using this type of system.

So why isn’t NASA building BDBs? In several of his columns, Mr. Schnitt describes his experiences with the Office of Technology Assessment, the technical/scientific arm of Congress. He says that these experiences convinced him "that Congress was more interested in maintaining the status quo desired by industry and the procurement agencies rather than in lowering the cost of space operations."

Of course, the ultimate goal in the space industry is to forget about boosters entirely and just build an SSTO (Single Stage To Orbit) system. This is the idea of spending five dollars on a nice cup that can be reused instead of a paper cup that is thrown out. The space shuttle was supposed to be a step in that direction, yet it still uses boosters that are dumped in the ocean. While these are later recovered and refurbished, it has been argued that the cost of doing so equals or exceeds the cost of mass producing them for one time use.

Perhaps giant kerosene cans are the answer. Maybe Big Dumb Boosters would save the taxpayers money and make it more feasible to establish a serious presence in space.