Deeper into Jeopardy! XLVII: Oxygen – $1200

Jeopardy! category: OXYGEN (30-6-2015)

$1200 clue: The turboram type of this engine on certain planes mixes liquid oxygen with the fuel to support combustion

Correct response

The gist: I’m not even going to pretend to be able to explain how this works. Turborams are a type of jet engine that combines aspects, appropriately of both the turbojet engine and the ramjet engine. Jet engines, on an extremely simple level, work by compressing air from the atmosphere, combining it with some fuel, and then igniting said fuel, which causes the air to heat up and expand very, very quickly and shoot out the business end, creating thrust that pushes whatever the engine happens to be attached to forward.

Sadly, if that thing happens to be an aircraft, this introduces an important limitation. As an aircraft increases its altitude, the concentration of oxygen gas in the air around it decreases – if the craft goes too high, there can be insufficient oxygen to ignite the fuel that expands the gas. Turborams solve this problem by carrying the gas with them – usually a mix of liquid hydrogen and oxygen – and injecting the liquid into the combustion chamber when needed. This is the same principle that drives a rocket engine, which carries with it all the propellant it requires. A turboram goes one step further, however. Where a regular turbojet engine uses an axial compressor (that big fan thing inside a jet engine) to compress its air, a ramjet engine works at high enough speeds that it doesn’t require a compressor – it just relies on its speed to compress the air inside it. This is much simpler to use and more efficient than a turbojet, but needs to be accelerated before it can work. A turboram is meant to combine the strengths of both these types of engines, using the turbojet to accelerate from a standstill and the ramjet when it gets up to speed.

A complicated-looking diagram of the two stages of a turboram. At the top, the air passes through the compressor, like in a regular jet engine. At the bottom, the intake guides have redirected the air around the compressor, relying on the craft's speed to compress the air, like a ramjet.

A complicated-looking diagram of the two stages of a turboram. At the top, the air passes through the compressor, like in a regular jet engine. At the bottom, the intake guides have redirected the air around the compressor, relying on the craft’s speed to compress the air, like a ramjet.

The clue: Besides the fact this clue reads terribly, it really goes out of its way to hide the salient details. Most people, seeing a question about planes and engines, will logically guess “jet,” but it’s not really clear that that’s the sort of thing it’s looking for. I suspect that it was the writing, and not the subject matter, that led to this one going down as a Triple Stumper.

In Jeopardy!: For such an awesomely cool invention, I’m surprised that the jet engine is in just 20 regular and one FJ! clue in the J!Archive, and there really isn’t much common ground between them. It’s often used as a comparative for volume, or as an example of a product made by some company or other (like GE, Rolls Royce, BMW, or Pratt and Whitney), or for physics questions. Remember, jet engines produce thrust (in three clues), and they involve air compression (another three). That’s really, strangely, most of the commonalities between them. Take a look.

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