The First Internal Combustion Engine To Go Into Outer Space

July 7, 2016 9:50 AM

At 600 cubic centimeters and 26 horsepower an internal combustion engine under development by Roush Fenway Racing is among their smallest and least powerful. It also will be the first internal combustion engine to go into outer space.
posted by Rob Rockets (44 comments total)

We're going to put a straight 6 into space.

This is quintessentially 'Murica.
posted by NoxAeternum at 9:57 AM on July 7, 2016 [10 favorites]

I wonder what they're doing about lubrication? Earthbound applications for piston engines, even airplane engines, rely on gravity to some extent to keep oil recirculating. A dry sump with some kind of check valve, mist accumulator, and multi-point pumping?
posted by 1adam12 at 10:03 AM on July 7, 2016 [5 favorites]

Plus, the best part of all is that running the combustion engine is essentially free: the engine runs off the hydrogen and oxygen that normally is lost to boil-off, anyway.

That's very clever.
posted by Anticipation Of A New Lover's Arrival, The at 10:03 AM on July 7, 2016 [5 favorites]

Changing the oil every 3000 miles is going to get expensive
posted by kleinsteradikaleminderheit at 10:08 AM on July 7, 2016 [12 favorites]

Rocket 88 was prophetic. Alternatively.
posted by dances_with_sneetches at 10:11 AM on July 7, 2016

There goes the window for Top Gear's Reliant Robin experiment, I guess.
posted by Holy Zarquon's Singing Fish at 10:15 AM on July 7, 2016

Take that, Elon Musk!
posted by leotrotsky at 10:16 AM on July 7, 2016 [1 favorite]

Just how retro are they willing to go?

"Although modern guidance systems are incredibly accurate, we opted to pair the internal combustion I6 with a vintage Delco 'three on the tree' shifter and BorgWarner manual transmission to allow for better propulsion system modulation during close maneuvers.

"The pine-shaped air freshener was Bob's idea."
posted by mosk at 10:21 AM on July 7, 2016 [8 favorites]

Four-on-the-floor with a classic Hurst shifter or GTFO
posted by Greg_Ace at 10:38 AM on July 7, 2016 [2 favorites]

You've got H2 and O2 right there and somehow all those moving parts are a better answer than a fuel cell?
posted by Western Infidels at 10:44 AM on July 7, 2016 [2 favorites]

I wonder what they're doing about lubrication? Earthbound applications for piston engines, even airplane engines, rely on gravity to some extent to keep oil recirculating. A dry sump with some kind of check valve, mist accumulator, and multi-point pumping?

Also the degradation of the lubricant. Even though they're burning hydrogen and oxygen they're still going to have minor amounts of lubricant in the combustion chamber being burned off both as a matter of physics and to provide the sacrificial layer of ash on a valve to prevent recession. It's not going to last forever.
posted by Talez at 10:45 AM on July 7, 2016

You've got H2 and O2 right there and somehow all those moving parts are a better answer than a fuel cell?

The idea is that exhaust pressure can be used as an altitude control system and for axial thrust, something fuel cells can't do at all.
posted by Talez at 10:48 AM on July 7, 2016 [4 favorites]

It's not going to last forever. True, but to be fair, it doesn't need to. The odometer on your vehicle might be spinning like a slot machine but you're probably not going to need this thing to still be chugging one year later.

I have to admit that I was kind of primed to hate this idea but it looks promising. I definitely have questions, but it's clear that smarter people than me are working on it. That's the great thing about rocket science.
posted by phooky at 10:55 AM on July 7, 2016 [2 favorites]

I just realized a few minutes later that this engine won't have valve recession burning pure H2 and O2. Since there's no sulphur in the fuel you won't get SOx and because there's no nitrogen in the air you won't get NOx. No SOx and NOx means no acid which means no reason to coat the valve in a base like ash or use detergents in the fuel.
posted by Talez at 11:01 AM on July 7, 2016 [3 favorites]

Wish it was Hendrick Motorsports and not Rousch Fenway, but it is very cool nonetheless. (Not for Junior, but for Chase Elliot, son of Awesome Bill from Dawsonville!)
posted by AugustWest at 11:04 AM on July 7, 2016 [1 favorite]

Currently, rockets use a combination of heavy batteries and solar cells for electrical power, hydrazine for attitude control and tank settling thrusters, and helium for tank pressurization. It’s a lot of complex, separate systems that take up a lot of weight—often around 15-20% of total spacecraft mass. That’s a lot.

What IVF hopes to do in ULA’s Vulcan rocket upper stage is to eliminate the complexity and mass of the current way of doing things by limiting fluids to liquid hydrogen and oxygen, and using an internal combustion engine—like the ones used in cars for over a century—to provide electrical power, heat for vaporizing fluids to act as pressurants, and settling thrust from exhaust, all for much less weight than batteries and multiple fluid storage tanks.

Or like Alton Brown is always saying, there's no room in this rocketship for a unitasker.
posted by notyou at 11:07 AM on July 7, 2016 [3 favorites]

Hot Rods in Space!

As much as there are many alternatives, generating electricity from a generator is often the most effective technology.
posted by sammyo at 11:16 AM on July 7, 2016 [2 favorites]

The idea is that exhaust pressure can be used as an altitude control system and for axial thrust, something fuel cells can't do at all.

Using the exhaust from an IC engine can't be the most efficient way to get thrust from hydrogen+oxygen, though—surely a small combustion chamber and rocket nozzle would be lighter and produce more thrust.
posted by The Tensor at 11:29 AM on July 7, 2016

Using the exhaust from an IC engine can't be the most efficient way to get thrust from hydrogen+oxygen, though—surely a small combustion chamber and rocket nozzle would be lighter and produce more thrust.

Indeed but this ICE both runs on the boil off from the tanks that would normally be not wanted/unusable by a rocket engine and vented into space and also performs auxiliary power functions as well all in the same unit.
posted by Talez at 11:44 AM on July 7, 2016 [3 favorites]

Oh and LH2/LOX combustion requires an ignition system which makes it particularly useless for a thruster for attitude control.
posted by Talez at 11:50 AM on July 7, 2016 [2 favorites]

Rocket 88 was prophetic. Alternatively.

Or these guys from around 30 AD.
posted by Harald74 at 12:02 PM on July 7, 2016

1adam12: "I wonder what they're doing about lubrication? Earthbound applications for piston engines, even airplane engines, rely on gravity to some extent to keep oil recirculating. A dry sump with some kind of check valve, mist accumulator, and multi-point pumping?"

I would really like to see some details on this. How the heck are they preventing the lubricant from being whipped into foam by the bottom of the pistons while still lubing the cylinder walls? Some sort of positive crankcase scrubber?
posted by Mitheral at 12:06 PM on July 7, 2016

How is this not the first legitimate application for the hilariously named Wankel engine?

Better weight-to-power ratio, no vibrations, fewer moving parts/points of failure... And since fuel is free, efficiency doesn't matter. Also in space, nobody smells the unburnt fuel in the exhaust stream.
posted by kleinsteradikaleminderheit at 12:09 PM on July 7, 2016

The article explains that the Wankel was ruled out due to producing too much heat.
posted by bdc34 at 12:16 PM on July 7, 2016 [3 favorites]

Zero and negative G engine lubrication systems are used in piston-driven aerobatic airplanes. Basically a combination of flexible pickup and check valves.

Interesting stuff about the torque and intake consistency of the straight 6 design, and not needing a flywheel.
posted by maniabug at 12:16 PM on July 7, 2016

How is this not the first legitimate application for the hilariously named Wankel engine?

Because they can't just head up there and rebuild the engine when the apex seals start to fail.
posted by Talez at 12:16 PM on July 7, 2016 [7 favorites]

bdc34: "The article explains that the Wankel was ruled out due to producing too much heat."

I think it's actually the opposite. Or at least that the I6 produces more easily harvestable heat. Also I think an I6 is where you start being able to easily design a four stroke engine where at least one intake port is open at any one time. That is a pretty big benefit with gaseous fuels.
posted by Mitheral at 12:29 PM on July 7, 2016 [2 favorites]

"Now, if you just slip into that suit right there and hook up a tether, Jerry, we can step outside and pop the hood."
posted by CynicalKnight at 12:30 PM on July 7, 2016 [1 favorite]

The article says the I6 gives you more surface area to extract waste heat than a Wankel, allowing for a more efficient cooling system.
posted by cardboard at 12:33 PM on July 7, 2016 [1 favorite]

Indeed but this ICE both runs on the boil off from the tanks that would normally be not wanted/unusable by a rocket engine and vented into space and also performs auxiliary power functions as well all in the same unit.

Suppose you have hydrogen and oxygen boiling off from tanks, and you want power and thrust. Consider two options:

1. Plumbing to carry H and O gas to the IC engine, which produces power, then more plumbing to carry the exhaust gasses to attitude jets.
2. Plumbing to carry H and O gas to a fuel cell, which produces power, and more plumbing that carries H and O gas to attitude jets.

How can the first option be less weight and complexity than the second? Does an equal-power IC engine weight less than a fuel cell, so they're trading weight for complexity?
posted by The Tensor at 12:40 PM on July 7, 2016

I don't know, but they're literally rocket scientists, so I'm sure they know what they're doing.
posted by Monochrome at 12:56 PM on July 7, 2016 [2 favorites]

The exhaust is the combustion of hydrogen and oxygen, which heats the exhaust gasses and makes their expulsion more forceful, while at the same time generating electricity and waste-heat, which is used to pressurize the tanks.
posted by Slap*Happy at 12:57 PM on July 7, 2016 [1 favorite]

A straight 6 into space. Grandpa is looking down on this and smiling. His favorite truck was the F-150 with a straight 6 and a 3 speed. "They run strong and they're easy and cheap to fix."
posted by azpenguin at 1:13 PM on July 7, 2016

I bought a brand-new air-mobile
Custom-made, 'twas a Flight De Ville
With a pow'ful motor and some hideaway wings
Push in on the button and you will hear her sing

Now you can't catch me
Baby you can't catch me
Cuz if you get too close, you know I'm
Gone like a cool breeze

posted by Herodios at 1:17 PM on July 7, 2016 [1 favorite]

Plumbing to carry H and O gas to a fuel cell, which produces power, and more plumbing that carries H and O gas to attitude jets.

Attitude control is quick, short bursts of thrust. LOX/LH2 requires an ignition sequence of several seconds before it can provide thrust. This is why we use N2H2 monopropellent for thrusters. The monopropellent and associated plumbing is the bargain you're trying to beat.
posted by Talez at 1:58 PM on July 7, 2016 [2 favorites]

I understand why doing away with the secondary propellant system might be a win, especially if they're able to use H and O they were going to vent anyway. Having decided to do that, though, I don't understand why an IC engine is better than a fuel cell. Are fuel cells heavier than the corresponding IC engine, power-for-power? You can react the H and O (with the same H₂O exhaust) to produce power to pressurize the fuel either way—why prefer the solution with all those moving parts?

For comparison: NASA is designing a new radioisotope power generator that uses a Stirling cycle engine (moving parts!) instead of thermocouples to produce electricity. This is more complex, but it's four times as efficient at turning heat into electricity, so they can use 1/4 as much plutonium, which makes it worthwhile.

Is an IC engine similarly more efficient than a fuel cell? (Some poking around the web implies it's the other way around.) Maybe efficiency doesn't matter because you're going to throw away most of the excess H and O anyway. OK, does an IC engine have higher peak power output than a fuel cell? Is it more throttleable? Is it lighter?

You just can't seriously expect people to READ the article before giving their considered opinions and superior suggestions!

I'm asking here because I'm interested in the subject and TFA doesn't mention fuel cells at all. If you don't want to discuss it, feel free not to discuss it.
posted by The Tensor at 2:24 PM on July 7, 2016

Getcha motor runnin' ......

I got nothin'
posted by jonmc at 2:26 PM on July 7, 2016

There's a lot of discussion about fuel cells and Wankels in the nasaspaceflight forum, including some posts by one of the designers.

The tl;dr of "why not a fuel cell" is that a) you need torque to drive pumps to pressurize the fuel anyway so you'd need a motor and b) efficiency in terms of heat is actually bad, what's 'waste' heat on earth is valuable in a rocket.
posted by Skorgu at 3:17 PM on July 7, 2016 [3 favorites]

Something not apparent from the article is that this engine would probably not be running continuously, but would be fired up when the stage needs to perform a burn. The whole idea of this project is to produce a LH2/LOX rocket stage with a life of weeks or months rather than hours, so the requirement is for power, heat and ullage thrust for short periods with long coast periods between.

As such, having an engine running a generator is probably more efficient than fuel cells, which are better for prolonged operation at a lower power level. Also, fuel cells produce low voltage DC power, whereas a motor turning a generator can produce high voltage AC, which allows for more efficient power transfer (especially at relatively high frequencies; this is why aircraft electrical systems run at 400 Hz rather than 50 or 60 Hz.)
posted by Major Clanger at 3:22 PM on July 7, 2016 [1 favorite]

As to why not a Wankel, the article touches on it but doesn't go very deep. I'm pretty familiar with them, and I can understand why NASA would take a pass.

I suspect the Wankel was considered early precisely due to its heat-transfer characteristics. In the same way that a flat head piston engine has a huge amount of exhaust port area, a side-port rotary engine does too. Add to that the fact that the combustion chamber is extraordinarily long and you get lots and lots of heat transfer into the rotor housings. What's a big problem on earth becomes a big asset in space.

Why aren't they a winner, then? Wankel engines rely on oil being injected into the combustion chamber to lubricate the apex seals (think "piston rings") that separate the combustion chambers. That means you get combusted oil, and lubrication is not a closed system. Add to that the fact that Wankels aren't nearly as well-studied as Otto-cycle engines, and there are probably just too many unknowns.
posted by TheNewWazoo at 5:48 PM on July 7, 2016 [2 favorites]

Yeah, it seems what they're looking to achieve is some machine or combination of machines that can use waste H₂ and O₂ as a source of several types of power rockets generally need: electricity, torque for pumps, exhaust for ullage and maneuvering thrust, heat for vaporizing their liquids to pressurize their tanks. So they could do one step of that more efficiently with a fuel cell: convert H₂ and O₂ into electricity. But then for the full system they'd need electric motors to turn pumps, electric heaters to pressurize tanks, something else to provide thrust, and all those other energy conversions would stack more inefficiencies on top.

Compared to that it's not unsurprising that an internal combustion engine, creating torque and heat and thrust simultaneously as an inherent property of how it works, might end up being more efficient. Which is neat because here on Earth in cars that's the opposite of true, hence all the fuel-cell interest. Although from the diagram it looks like, while they use the piston engine exhaust for ullage thrust, they don't use it for maneuvering, and instead have separate GH₂+GO₂ rocket engines for that. I guess that's easier to ignite than if they used liquids?
posted by traveler_ at 6:18 PM on July 7, 2016 [1 favorite]

Perhaps they also want to avoid detection by bad guys.

He again shut off his atomics and started the sixteen-cylinder Diesel engine which would do its best to replace them. That best was none too good, but it would do. Besides driving the Bergenholm it could furnish enough kilodynes of thrust to produce a velocity many times greater than any attainable by inert matter. It used a lot of oxygen per minute, but it would not run for very many minutes. With her atomics out of action his ship would not register upon the plates of the long-range detectors universally used. Since she was nevertheless traveling faster than light, neither electromagnetic detector-webs nor radar could “see” her. Good enough.

--First Lensman by "Doc" Smith.
posted by Autumn Leaf at 7:03 PM on July 7, 2016 [1 favorite]

Getcha motor runnin' ......

Ride out on the skyway!
Looking for science, or whatever comes our way!

Yeah, rocket gonna make it happen!
Take the world in a loving embrace!
Fire all of your engines and
Explode into space!

I like LOX and Hydro
Rocket engine thunder!
Racing in the atmosphere
And the feeling that I'm under!

Like a true I.C.E.!
We will rev until we be
Electricity and waste heeeeeeaaaaat...

BORN TO BE WIIIIILD!
posted by Slap*Happy at 7:54 PM on July 7, 2016 [4 favorites]

I am still at a loss as to how In Vitro Fertilisation helps rockets.

Oh wait...this has all been one giant euphemism, hasn't it?
posted by rum-soaked space hobo at 3:42 AM on July 8, 2016