Author Topic: ULA Innovation: Integrated Vehicle Fluids (IVF) (Read 147118 times)

sanman · « **Reply #160 on:** 04/20/2015 08:21 pm »

Hi Mr Zegler,

You've mentioned how you coupled the ICE to the PEM, but when considering ultracapacitors and/or battery pack, then how far did they fall short of the mark? Did you investigate any possible use of superconductive motors to drive compressors, since you have cryogenic propellants available to provide cooling?

If Wankel rotary engines were considered, then what made them disadvantageous? I'd read that Wankels have higher power-to-weight ratio compared to reciprocating piston engines, while also isolating the fuel inlet from the combustion for added safety.

Do you still see ultracaps, superconductive motors, Wankel rotary engines as possible future upgrade paths?

jg · « **Reply #161 on:** 04/20/2015 09:13 pm »

Quote from: sanman on 04/20/2015 08:21 pm

If Wankel rotary engines were considered, then what made them disadvantageous? I'd read that Wankels have higher power-to-weight ratio compared to reciprocating piston engines, while also isolating the fuel inlet from the combustion for added safety.

Frank already answered the Wankel question, if you read his previous responses carefully. Roughly, Wankel's can have the same sort of problems that doomed a turbine, given no nitrogen in the fuel; the wearing part of the Wankel will get too hot with insufficient area to dissipate the heat...

the_other_Doug · « **Reply #162 on:** 04/20/2015 09:28 pm »

Quote from: jimvela on 04/20/2015 07:38 pm

Quote from: Designvis on 04/20/2015 07:18 pm
Frank Zegler of ULA here to answer a few questions about the IVF architecture and how we got to where we are.

Thank you for taking the time to comment.
Kudos to ULA for engaging through NSF- you will find the signal to noise ratio very high here...

Yes, thanks, Dr. Ziegler! You've addressed my issues very nicely. I'm feeling a heck of a lot more confident in the IVF technology than I was before.

DatUser14 · « **Reply #163 on:** 04/20/2015 09:42 pm »

Dr Ziegler, first of all thanks for doing this. How will the IVF technology fit on Centaur (and eventually ACES). Is it being designed to fit in the existing compartments or will the stage be redesigned?

Damon Hill · « **Reply #164 on:** 04/20/2015 11:05 pm »

IVF embodies the KISS principle: if it doesn't need to be complicated, Keep It Simple. That almost always saves money and improves reliability. Better to impress with simple elegance than complex technology.

Most of the bulky stuff (hydrazine and helium tanks, batteries, at least some electronics) is mounted on the bottom of the LOX tank adjacent to the RL10 engine(s). The IVF systems are fully contained on a single and fairly compact platform that will mount in the same locations and look kind of lonely with all of the previously mentioned hardware now eliminated. Two such platforms will be used partly for redundancy.

TrevorMonty · « **Reply #165 on:** 04/21/2015 12:36 am »

Thank you Frank for answering our questions.

What is the fuel consumption (LH & LOX in kg/hr) for ICE at 20KW?

What is the expected weight savings on a IVF Centuar?

Designvis · « **Reply #166 on:** 04/21/2015 06:53 pm »

Frank Zegler of ULA. I'm glad you folks are interested in this concept. Its consumed me for getting a decade and has lots of fascinating aspects.

Regarding orbital testing: We would have needed a test lab that could handle liquid hydrogen and oxygen in fairly large quantities. Doing testing at ISS is challenging even when you are not proposing to light large fires or manipulate cryogens under high heat transfer conditions. Eventually we will need an orbital facility that can do this but we are decades away from this I fear. Once this is in place we will learn at an accelerating pace since we will be able to rapidly interact with a test article on a daily basis. That is how you really learn what works and what doesn't.

Regarding Wankel Engines
We chose this as our initial prime focus since these things are light, simple and have very high power/mass ratios. Kind of like a compromise between turbine and reciprocating engine. Plus no valve system and the induction system is not subject to combustion pressures and temps. Plus at the time we were only looking for around 5kW- it was an earlier iteration of the IVF system with liquid instead of gas compressors. It extracted heat energy from the thrusters instead.... but I digress.

Combustion in a Wankel happens in the same place for every ignition- unlike in a 4-stroke multi-cylinder engine. That area never gets an exhaust or intake stroke to cool down. H2/O2 combustion is a beautiful thing- it should be in every IC engine textbook as the perfect combustion process. You should see how crummy gasoline or even natural gas burn. it is astonishing you can actually make gasoline engines run as well as they do. It is a tribute to the skills of the automotive engineers that they can do this. Anyway H2 combustion happens fast and is incredibly repeatable. It is also intense and the heating at the ignition source is very high. This limits the peak MR that can be tolerated. The rest of the Wankel is dead cold by comparison- this creates incredible dimensional distortion problems. Cooling the rotor is another issue and of course lubricating the side seals and apex seals is highly non-trivial. We investigated the internal lubrication systems on three commercial Wankel engines and were blown away by the sophistication required to get these engines to run properly. We saw a huge thermodynamic and tribology project ahead of us. Compound that with the non-redundancy of the single rotor and we did not see an affordable and reliable path forward.

We had incredible success with the thruster and actually built two types. One was a higher pressure pulsed motor like a typical hydrazine thruster that was intended for maneuver. We also built one for vehicle settling that had heat rejection systems built in and operated at very low chamber pressures since it was only fed by ullage gases. This low pressure was a significant risk item. Once we showed excellent ignitions we realized that we didn't need both types and could consolidate to one even simpler design and field it sooner.

Since we wanted reliability and simplicity the 6 cylinder was a clear choice due to its smooth power delivery, low vibration, dispersed heat rejection and wider MR capability. Even the smallest six cylinder ( we used the smallest practical pistons for example) could produce much more power though- which was fine since we could use the waste heat from the ICE alone to drive the pressurization process. The greater power permitted gas compressors which drastically simplified their design too. That design step enabled tank pressurization without mass addition and that made a huge difference to system performance.

Regarding Batteries and ICEs
It is critical to understand that when we say the IC engine is a 20kW machine we are quoting the shaft power only. In most heat engines the waste Q is just that- waste. In IVF we use the wall Q completely and hence the actual usable energy output of the ICE is at least twice what we quote when talking shaft power. So working together the two IVF modules can deliver up to 80 kW of enthalpy rise to the vehicle tanks. This is conservative. In addition we use the remaining energy in the ICE exhaust for settling. So the utility of the energy released is very high.

No doubt you could store up energy in a battery system to run compressors and heaters but you would be rejecting the waste heat from a fuel cell for example during that charge period and it would be lost. To match the ICE architecture the battery system would really have to release twice the power or thereabouts.
IVF has small lithium ion batteries that run at 300V and they have awesome power capability to handle spike loads- almost as big as the ICE output. But to reliably handle an 80kW demand for hundreds of seconds while maintaining the battery voltage in a reasonable band would drive the mass up considerably- well in excess of the ICE. Like all hybrid systems there is trade between the prime mover mass and the energy storage system mass. A balance must be struck based on peak vs average power and practical limitations.

Regarding Super-Caps
We are still investigating these but so far their energy density and system support flexibility is inferior to Lithium batteries. The jury is still out for specific areas.

Regarding the IVF installation
The two IVF modules are intended to be mounted to the aft area of an upper stage and they will be tested together with their interconnecting structure, plumbing and harnessing as a unit. They are extremely compact units- 900mm long, 600mm wide and depending on where you measure (due to thrusters protruding) either 800mm or 600mm tall.

The target mass for this entire IVF installation is 500 lbm. Performance savings are complicated by the reduction in consumables like hydrazine and helium. The IVF capabilities are so much larger that to make a matching traditional system is rather impractical. That makes comparisons difficult or meaningless. Suffice it to say that if you were just doing 15 minute launches to LEO you would likely not select IVF. That is the mission scenario that ICBMs were optimized around more or less. IVF would be lighter but not by enough to justify the investment. Our challenge is to reduce system mass (and cost) for the simple missions (LEO) and yet provide a capability that simply cannot be matched for more advanced multi-day missions. When you are talking about these kinds of missions the mass savings can be in the tons. So the answer is that the savings vary from hundreds of pounds to many thousands.

Regarding Motors
How you take power off of the ICE is a matter of choice depending on what you intend to do with it. It is presently being done mechanically and via generators. There is much to recommend both depending on the overall power flow and practical issues like gearboxes, lubrication, power switching etc. If you want to read a great document showing how such hybrid systems are engineered look at the report from Oak Ridge Labs about the 2010 Prius teardown they did. Much of the design those Toyota engineers did is very similar to IVF. Beautiful design really.

Oh and by the way I'm not a doctor.

Malderi · « **Reply #167 on:** 04/21/2015 08:23 pm »

Frank, your recent posts are some of the best on this forum for design insight. Thank you so much for taking the time to write them for us.

You mentioned the mass savings end up varying considerably based on the type of mission, which makes sense. Can you talk about what design reference missions, if any, you've used for design optimization?

Damon Hill · « **Reply #168 on:** 04/21/2015 10:15 pm »

I have a mental image of a Centaur/ACES putt-putting its way on a TLI trajectory, leaving little sequential frost-puffs in its wake...

Has the Isp of the engine exhaust been estimated? I know the thrust is miniscule but it should keep the propellant settled.

john smith 19 · « **Reply #169 on:** 04/21/2015 10:49 pm »

Mr Ziegler,

Thank you for your very lucid description of the current system and the design choices that produced it. -

It was fascinating to see how, as the test results and analyses came in the design morphed the Wankel as prime mover gave way to the 6 cylinder in line, while the the separate settling and attitude thrusters merged into one common design.

One thought struck about the Wankel design. The highly localized heat release of the Wankel reminded me of that produced by the CPU of high end lap tops. In that application heat pipes have been used to spread the load across the whole of the base. I wondered if there would be enough mass in a Wankel engine block that you could spread the heat, giving an overall "warm" block (probably too hot to touch but nowhere near melting) giving a larger surface area to tap the heat from. This is obviously hindsight now the I6 is the engine of choice.

AFAIK everyone who's aware of IVF (however it's implemented) thinks it's a really clever idea. It's just a pity that it doesn't look like it will get a flight slot before 2018.

sdsds · « **Reply #170 on:** 04/23/2015 07:19 pm »

Interplanetary trajectories (to Mars or asteroids) have been studied that include "broken plane" maneuvers part way through the coast phase of the transfer. These can reduce overall delta-v and perhaps more importantly reduce the delta-v requirement to orbit or rendezvous with the destination. I'm wondering if ULA is proposing use of a long-lived (IVF) upper stage to perform this kinds of broken plane trajectory? Or would the time of flight before the maneuver be too challenging?

georgesowers · « **Reply #171 on:** 04/23/2015 08:18 pm »

Quote from: sdsds on 04/23/2015 07:19 pm

Interplanetary trajectories (to Mars or asteroids) have been studied that include "broken plane" maneuvers part way through the coast phase of the transfer. These can reduce overall delta-v and perhaps more importantly reduce the delta-v requirement to orbit or rendezvous with the destination. I'm wondering if ULA is proposing use of a long-lived (IVF) upper stage to perform this kinds of broken plane trajectory? Or would the time of flight before the maneuver be too challenging?

Variations of our distributed lift architecture could do a mission like this. ACES with attached drop tank.

Prober · « **Reply #172 on:** 04/30/2015 02:20 am »

Quote from: Designvis on 04/21/2015 06:53 pm

Regarding Motors
How you take power off of the ICE is a matter of choice depending on what you intend to do with it. It is presently being done mechanically and via generators. There is much to recommend both depending on the overall power flow and practical issues like gearboxes, lubrication, power switching etc. If you want to read a great document showing how such hybrid systems are engineered look at the report from Oak Ridge Labs about the 2010 Prius teardown they did. Much of the design those Toyota engineers did is very similar to IVF. Beautiful design really.

Oh and by the way I'm not a doctor.

This Toyota fuel cell auto sure impressed me.....enjoy

kevin-rf · « **Reply #173 on:** 04/30/2015 12:37 pm »

Yeah, and Toyota is saying the Mirai will be half the price of a Tesla.

(Mirai is the fuel cell vehicle toyota will be selling in 2015)

sdsds · « **Reply #174 on:** 09/20/2015 06:14 am »

What's the current thinking about the first mission on which IVF-Centaur will fly? Is there a USAF payload that makes sense for this? Or with the reemergence of commercial customers on Atlas (e.g. Morelos 3), could it be one of them?

john smith 19 · « **Reply #175 on:** 10/23/2015 11:49 am »

Quote from: sdsds on 09/20/2015 06:14 am

What's the current thinking about the first mission on which IVF-Centaur will fly? Is there a USAF payload that makes sense for this? Or with the reemergence of commercial customers on Atlas (e.g. Morelos 3), could it be one of them?

I found this item.

http://www.ulalaunch.com/uploads/docs/Published_Papers/Supporting_Technologies/Orbital_Disposal_of_Launch_Vehicle_Upper_Stages_final.pdf

It seems fairly recent and they are talking specifically about a flight test in June 2016 for disposal of upper stages. However they also talk of using fuel cells, which I thought was pretty much off the table.

Apparently upper stage disposal is tough, especially if the payload was bound for GEO. Tapping remaining propellant lets you put it in an orbit with a low probability of collision, which seems to be better than one which (eventually) decay to reentry, but in a fairly random way and hence could hit something on the way down.

I really hope this is going ahead. It will demonstrate (partly) the IVF concept works and gather operating data to help refine the design

ULA had done their 100th consecutive successful launch, as measured by their customers. As the first of the IVF flight trials it could be even more important to the company.

Newton_V · « **Reply #176 on:** 10/23/2015 04:35 pm »

Quote from: sdsds on 09/20/2015 06:14 am

What's the current thinking about the first mission on which IVF-Centaur will fly? Is there a USAF payload that makes sense for this? Or with the reemergence of commercial customers on Atlas (e.g. Morelos 3), could it be one of them?

H2/O2 thrusters will probably fly well before IVF. Probably not on a government mission anytime soon. Nobody wants "unnecessary features" on their mission.

I suspect a commercial mission will be the first flight.

Prober · « **Reply #177 on:** 10/23/2015 04:49 pm »

Quote from: john smith 19 on 10/23/2015 11:49 am

Quote from: sdsds on 09/20/2015 06:14 am
What's the current thinking about the first mission on which IVF-Centaur will fly? Is there a USAF payload that makes sense for this? Or with the reemergence of commercial customers on Atlas (e.g. Morelos 3), could it be one of them?
I found this item.

http://www.ulalaunch.com/uploads/docs/Published_Papers/Supporting_Technologies/Orbital_Disposal_of_Launch_Vehicle_Upper_Stages_final.pdf

It seems fairly recent and they are talking specifically about a flight test in June 2016 for disposal of upper stages. However they also talk of using fuel cells, which I thought was pretty much off the table.

Conventional Hydrogen/oxygen yes they would be off the table. However, two other fuel cells I know of would work in that platform. One might work extremely well with the right catalyst.

john smith 19 · « **Reply #178 on:** 10/23/2015 06:37 pm »

Quote from: Prober on 10/23/2015 04:49 pm

Conventional Hydrogen/oxygen yes they would be off the table. However, two other fuel cells I know of would work in that platform. One might work extremely well with the right catalyst.

No I mean the point of IVF is that the 6 cylinder engine provides main tank pressure by heating the tank gases. Fuel cells don't really do that. One of the features of the IVF was the realization that heat is not a "waste product" but something to be used. Fuel cells simply don't provide this.

sdsds · « **Reply #179 on:** 10/23/2015 07:21 pm »

So does the WorldView 4 mission seem likely as the first test of the gaseous H2-O2 thrusters? This payload was called GeoEye 2 when it was sent to long term storage back in 2013....