They were heady days, the 1960s. Back then nothing seemed too big to engineer on Earth. Or off it.
When the moon race began in 1961, humanity had barely begun to step into space. But the job was done – twice. The Soviets had a serious programme, but started late, were under-funded, and work was divided between rival bureaux. Then Sergei Korolev died. With him died any chance of their N-1 moon booster working. The US equivalent, Wernher von Braun’s Saturn V, won the day.
Both derived from technologies von Braun pioneered in the 1930s. The Saturn V was a direct descendant of the V-2, with the same arrangement of traditional rocket engines and massive fuel tanks.
What that added up to was weight. It’s why a conventional single-stage rocket can’t make orbit with useful payload; too much mass is taken up in structure. Von Braun’s Saturn V managed a mass-ratio of 22 because it had three stages. The problem was that each stage was discarded after one use. Costs were astronomical.
However, they weren’t the only way ahead. In 1964, Douglas Aircraft engineer Philip Bono proposed a ‘plug nozzle’ engine that did away with the combustion chamber and complex cooling systems. Fuel (liquid hydrogen) was stored in jettisonable external tanks, with the oxidiser (liquid oxygen) inside the booster.
Bono called it ROMBUS – Reusable Orbital Module-Booster & Utility Shuttle. The design he and his associates came up with was enormous, with a launch mass of just over 6,300 tonnes. That was nearly twice the mass of a Saturn V, but the mass-ratio available in ROMBUS was good enough to fly to orbit in one hit, dropping external tanks along the way. What’s more, it could re-enter using the plug as a heat shield, pumping residual fuel across it as a coolant. And fly again, up to five or six times per booster. It was a different approach from carpeting the bottom of the Atlantic with dead Saturn stages.
Bono calculated that ROMBUS could put 450 tonnes into low Earth orbit, nearly four times that of Saturn V. The Moon was within reach of the system – and then Bono came up with a plan for flying one of his colossal boosters to Mars and back.
Bono estimated that ROMBUS could be flying by 1975 and drop launch costs to $12-per-pound to orbit, in 1964 terms. That compared wonderfully with the $150/pound of Saturn. Development costs were estimated at nearly $4.1 billion in 1964 dollars, this when the entire Apollo project was budgeted at $18 billion.
Technical issues relating to the plug nozzle would likely have taken some solving. Still, we can imagine the what-if scenarios. Project Selena looked towards a 1000-person lunar colony by 1984, and – providing ways could be found of stopping the cryo-fuels from boiling off during the 800-day mission – Project Deimos would have landed six astronauts on Mars by November 1986.
Bono’s huge rocket was a vision of its age – a vision of the 1960s, a vision of the era before humanity lost the dream, when anything seemed possible. But it never came to pass – and I can’t help thinking that today, that vision simply isn’t there.
Copyright © Matthew Wright 2014