ULA Innovation: Integrated Vehicle Fluids (IVF)

[john smith 19]

Hmm, perhaps it's a matter of semantics, but something on Centaur apparently requires mechanical shaft power that would take a 20 kW electric motor. I'm thinking that requirement is pumps, and those pumps are used to meet the RL10 startup propellant inlet pressure requirements. Is that wrong?

To be clear 20Kw is the total energy output of the engine.

The electrical part (from the paper) is about 4Kw (which is not minor if you're trying to do it with batteries on a continuous basis).

a big part of the rest is the "waste" heat from cooling the cylinders, which in reality is used to pressurize the tanks.

What's left over can be used to take the propellants and pump them to 10bar+. This can be used to pre pressurize the propellants to the RL10(s) or on their own, to deliver a 1200lb thrust thruster on it's own, although I'm not too sure what you would use this for, as that's a pretty poor T/W ratio of about 12:1.

[TrevorMonty]

For delivering fuel, boil off would be an issue over a few days of a flight (eg EML1/2 spacestation). With existing systems the boil off would have to be dumped or burnt in thrusters either way it is lost. With ICE IVF the boil off could be converted to water (ICE exhaust) and saved. The surplus water can be used by the space station or converted back into LOX and LH by fuel depot. 

[R7]

I've never understood precisely how XCOR's system really works; somehow I got the impression the piston pumps were to directly pump propellant; perhaps it's a very similar system to IVF's internal combustion engine?  I was a little skeptical but I didn't have much information to go on.

It's a piston pushed by gas driving directly another piston pumping liquid. Early prototypes had a single free piston, the newer ones have in-line 3 configuration. Have not seen schematic of the latter models but it seems there are connecting rods to a crankshaft to keep the pistons in sync and possibly extract rotational power (generator). Early prototypes had double acting pistons, doing work both ways, the intakes in the inline-3 suggest single-action setup.

The brochures speak of proprietary closed thermal cycle driving the pump, apparently the working gas is not vent overboard but fed into combustion chamber if the pressure is sufficient or dilluted into the pump inlet.

To be clear 20Kw is the total energy output of the engine.

No.

Under  nominal  mixture  ratio  conditions  of  1.0  and  feed  pressures  typical  of  ullage  conditions  the  ICE
will produce on the order of 20kW (26HP) of shaft power

[sanman]

It's a really elegant way to reduce complexity and costs, and raise payloads at the same time, while keeping the rest of the stage essentially the same hardware.  When looking at the thermodynamics, the choice of a good old-fashioned flathead six cylinder internal combustion piston engine starts to become more obvious.  Fuel cells and Wankel quasi-rotary engines were also considered.

Why didn't Wankel rotary engines make the final cut? They have a higher power-to-weight ratio, and at least cut off the inlet port from the exhaust port, which is safer.

[jg]

Because they start with off the shelf engine blocks from industry.  A Wankel they would have to design/build themselves.

[sanman]

There are off-the-shelf Wankels -- they're not all custom one-offs.

[Damon Hill]

A custom built inline six cylinder flathead engine was chosen because it has better heat recovery than a Wankel.  Also, the Wankel tested had hot spot/cooling issues running on hydrogen.  Off-the-shelf isn't relevant here and modern CNC machining keeps costs down.

There's a widespread misunderstanding that high thermal efficiency is of over-riding importance; the "waste" heat is actually very useful and desirable in this application for maintaining tank pressure and eliminating the helium system.  This is also partly why fuel cells were not chosen.  The hydrogen-rich hot exhaust is also used for propellant settling thrust, which helps to eliminate the hydrazine thruster system.

The piston engine uses direct oxygen injection to the cylinder and hydrogen is injected from the crankcase, which also scavenges blowby from the piston rings.

This explains the choice of engines and the development of the technology:

http://tinyurl.com/ula-ivf2012

[Remes]

I believe Earth ICEs usually run pretty close to stoichiometric but they're kept cool by all the nitrogen in air. Even to match typical Earth ICE temperatures you'd need tons of unburned hydrogen so I'm skeptical of the no-steel-needed conjecture (but am not an engineer). It's certainly plausible that they might run it that fuel-rich so I'm not saying it's wrong, just I'd like to see more evidence before I'm convinced.

Additionally to the fuel rich mixture ratio they might feed back some exhaust gas?

[the_other_Doug]

Unfortunately, they have frozen question submission in the thread where Dr. Sowers is answering them, right when I came up with a good question for him:

* * *

Concerning the previously announced IVF technology to be used in Vulcan, how far along is ULA in developing an internal combustion engine that can run on hydrogen and oxygen and survive the implied temperatures and pressures (plus the vibration regime of a solids-assisted launch), be able to maintain lubrication over weeks and/or months spent quiescent in orbit, etc.?

* * *

Knowing how many moving parts a piston engine must have, how the lubrication has to work, etc., etc., I have to say that my first reaction to the IVF announcement, and that it will use ICEs to power the technology, was that this is possibly the worst idea I've ever heard of.  But I'm not a rocket engineer -- even though I've had to do a lot of tinkering with ICEs over the years.

Well, maybe they'll open up the Q/A thread to new questions and I can sneak mine in...

[TrevorMonty]

All best with the Vulcan. It has turned me into a ULA fan and many others judging by forum activities and name voting.

Do ULA plan to introduce IVF on Centuar or will it wait for ACES?.

Business case to close. 
Thanks!  As Tory said in the press conference, we got well over 1.1M votes.

IVF is an integral part of the ACES design.  We would like to field it on Centaur earlier, but need to find the right opportunity to get the business case to close.  Without going into details, we are actively pursuing several possibilities.

Not a definitive answer but it looks like IVF will fly on Centuar first.
Can see a case for just flight testing ICE in space as a payload.

[russianhalo117]

All best with the Vulcan. It has turned me into a ULA fan and many others judging by forum activities and name voting.

Do ULA plan to introduce IVF on Centuar or will it wait for ACES?.

Business case to close. 
Thanks!  As Tory said in the press conference, we got well over 1.1M votes.

IVF is an integral part of the ACES design.  We would like to field it on Centaur earlier, but need to find the right opportunity to get the business case to close.  Without going into details, we are actively pursuing several possibilities.

Not a definitive answer but it looks like IVF will fly on Centuar first.
Can see a case for just flight testing ICE in space as a payload.

According to the ULA white papers that is the plan. they are linked somewhere in an above post.

[Damon Hill]

The ICE design draws on many decades of experience designing engines for aircraft, where lubrication can operate independently of gravity and wildly random orientation.  I imagine the lubricant is a synthetic oil that remains fluid at low temperatures.  Hydrogen and oxygen are fed to the engine as a gas, not a liquid.

It's all really very elegant thinking outside of the box.  There are times when seemingly old tech does the job right, at reasonable cost compared to more high tech solutions.

It seems one of the benchmarks of innovative thinking is how it cuts against the grain of preconceived notions.  There's been a LOT of confusion, but once you've studied the links to articles that explain the design in detail, you'll have a better notion of thermodynamics and enthalpy.  People have been stumbling over this subject since the steam engine was first built well over 200 years ago.

[TrevorMonty]

They can do a low risk approach and introduce IVF in stages.
1) Add IVF to existing Centuar. Complete mission using existing systems ie Hydrazine and He.
2) Once payload is deployed start the IVF tests.
3) Repeat until happy then switch to IVF.
There will be a payload penalty but for some missions this will not be an issue.

[russianhalo117]

They can do a low risk approach and introduce IVF in stages.
1) Add IVF to existing Centuar. Complete mission using existing systems ie Hydrazine and He.
2) Once payload is deployed start the IVF tests.
3) Repeat until happy then switch to IVF.
There will be a payload penalty but for some missions this will not be an issue.

only the early test flights, once legacy systems are retired it will have much lower mass than before IVF.

[arachnitect]

They can do a low risk approach and introduce IVF in stages.
1) Add IVF to existing Centuar. Complete mission using existing systems ie Hydrazine and He.
2) Once payload is deployed start the IVF tests.
3) Repeat until happy then switch to IVF.
There will be a payload penalty but for some missions this will not be an issue.

Can they test IVF on a legacy Centaur, or would the He interfere with IVF operation?

[baldusi]

They can do a low risk approach and introduce IVF in stages.
1) Add IVF to existing Centuar. Complete mission using existing systems ie Hydrazine and He.
2) Once payload is deployed start the IVF tests.
3) Repeat until happy then switch to IVF.
There will be a payload penalty but for some missions this will not be an issue.

Can they test IVF on a legacy Centaur, or would the He interfere with IVF operation?

From what I understood, they would test IVF after the mission is over so it doesn't interferes with anything. I would guess they would have to add some way to purge the He from the tanks before activating the system, which might add some weight. Probably not less than a 1000kg penalty, total. Which might explain why there's little desire to let this run along any payload.

[Damon Hill]

The presence of helium in the boiloff gasses was considered and not found to be a problem; terrestrial engines work happily with at least 70% nitrogen dilution.  Hydrogen burns over a very wide range of mixtures and the engine's direct oxygen injection probably compensates for helium dilution.  I get the impression there's almost nothing necessary for the engine to work as is.

Certainly the helium pressurization needs to be turned off, so autogenous pressurization and engine operation with straight hydrogen/oxygen can be properly evaluated.

[the_other_Doug]

Unfortunately, they have frozen question submission in the thread where Dr. Sowers is answering them, right when I came up with a good question for him:

* * *

Concerning the previously announced IVF technology to be used in Vulcan, how far along is ULA in developing an internal combustion engine that can run on hydrogen and oxygen and survive the implied temperatures and pressures (plus the vibration regime of a solids-assisted launch), be able to maintain lubrication over weeks and/or months spent quiescent in orbit, etc.?

* * *

Knowing how many moving parts a piston engine must have, how the lubrication has to work, etc., etc., I have to say that my first reaction to the IVF announcement, and that it will use ICEs to power the technology, was that this is possibly the worst idea I've ever heard of.  But I'm not a rocket engineer -- even though I've had to do a lot of tinkering with ICEs over the years.

Well, maybe they'll open up the Q/A thread to new questions and I can sneak mine in...

Sorry to quote myself, but I figured discussion on this is better here than in the Dr. Sowers Q&A thread.

I was able to sneak my question into the Q&A thread, and Dr. Sowers did say that they have a prototype engine that has several hundred hours of running under its belt.  That's a good start.  While I don't necessarily believe we'll ever see the details on how they're constructing the ICEs for their IVF approach, I'm really curious what kind of metals and materials they're using, and especially how they plan to lubricate an ICE in microgravity.  Without gravity to help your lubricant flow evenly over the moving parts, I'm having a hard time understanding how you don't develop "dry zones" that, with the temps implied by burning hydrogen and oxygen (without mediating gasses such as nitrogen or helium), would result in serious burn-throughs of rocker arms, valve lifters, and even engine blocks.

And, to be honest, there is no environment where it is remotely possible that they have been able to test their prototype engines for hours in microgravity.  The first tests in zero-G are going to be on the first flights of the IVF-enabled rockets.  Be a hell of a note if they discovered lubrication issues at that point.

I just have this image of a major Mars expedition being canceled because an ICE in an ACES upper stage threw a rod.  That would be a really bad day.

[TrevorMonty]

Aerobatic aircraft are even more demanding on their engine lubrication systems so ULA ICE shouldn't be a problem. NB engine doesn't run continuously, while coasting it is only needed to charge the battery occasionally.

[Damon Hill]

Unfortunately, they have frozen question submission in the thread where Dr. Sowers is answering them, right when I came up with a good question for him:

* * *

Concerning the previously announced IVF technology to be used in Vulcan, how far along is ULA in developing an internal combustion engine that can run on hydrogen and oxygen and survive the implied temperatures and pressures (plus the vibration regime of a solids-assisted launch), be able to maintain lubrication over weeks and/or months spent quiescent in orbit, etc.?

* * *

Knowing how many moving parts a piston engine must have, how the lubrication has to work, etc., etc., I have to say that my first reaction to the IVF announcement, and that it will use ICEs to power the technology, was that this is possibly the worst idea I've ever heard of.  But I'm not a rocket engineer -- even though I've had to do a lot of tinkering with ICEs over the years.

Well, maybe they'll open up the Q/A thread to new questions and I can sneak mine in...

Sorry to quote myself, but I figured discussion on this is better here than in the Dr. Sowers Q&A thread.

I was able to sneak my question into the Q&A thread, and Dr. Sowers did say that they have a prototype engine that has several hundred hours of running under its belt.  That's a good start.  While I don't necessarily believe we'll ever see the details on how they're constructing the ICEs for their IVF approach, I'm really curious what kind of metals and materials they're using, and especially how they plan to lubricate an ICE in microgravity.  Without gravity to help your lubricant flow evenly over the moving parts, I'm having a hard time understanding how you don't develop "dry zones" that, with the temps implied by burning hydrogen and oxygen (without mediating gasses such as nitrogen or helium), would result in serious burn-throughs of rocker arms, valve lifters, and even engine blocks.

And, to be honest, there is no environment where it is remotely possible that they have been able to test their prototype engines for hours in microgravity.  The first tests in zero-G are going to be on the first flights of the IVF-enabled rockets.  Be a hell of a note if they discovered lubrication issues at that point.

I just have this image of a major Mars expedition being canceled because an ICE in an ACES upper stage threw a rod.  That would be a really bad day.

The first mission of the demonstrator IVF module and subsequent full system without legacy components will likely be tense.  Sooner or later, new ideas have to flown in the real environment.

The design, construction and operation of the development engine, and the IVF concept in general, is described in considerable detail here:

http://tinyurl.com/ula-ivf2012

How many times does this have to be repeated before people start reading it?  This isn't a lawn mower engine with splash lubrication; it borrows directly from aircraft engine design with pressurized lubrication for all bearings and friction surfaces, a dry sump and centrifugal gas separator.  It's specifically designed for microgravity operation.

No doubt the operational design will differ in some details, and I hope ULA will publish those details.

--Damon