Info about the ULA new Vulcan stage

[magnemoe]

Pretty fun, they will use an 6 cylinder 600cc IC engine running on boil off for power. 

http://jalopnik.com/a-nascar-team-is-building-the-first-internal-combustion-1783198912

I guess the flow diagram is simplified as it don't show the pressurized tanks for H2 and O2, it also don't show the exec hydrogen went, or are they dropped?
Reason for 6 100cc cylinders is primary that it makes it run so smooth it dont need an heavy flywheel, its also redundancy as it will run even if one of the cylinders stop working. 

[p1t1o]

I guess it must have some advantage over a very small turbopump? A turbopump strikes me as smaller, lighter, simpler (fewer moving parts, increases reliability and reduces friction losses?) and already space-tested, and would still have the water vapour "exhaust" for propellant settling, and the rotary power could do all the same things as an IC engine. 

Perhaps a turbopump doesn't scale downwards well? They make a big deal of "smoothness" in the article, perhaps this is a factor?

[magnemoe]

10 minutes ago, p1t1o said:

I guess it must have some advantage over a very small turbopump? A turbopump strikes me as smaller, lighter, simpler (fewer moving parts, increases reliability and reduces friction losses?) and already space-tested, and would still have the water vapour "exhaust" for propellant settling, and the rotary power could do all the same things as an IC engine. 

Perhaps a turbopump doesn't scale downwards well? They make a big deal of "smoothness" in the article, perhaps this is a factor?

Well people has build turbines of car turbos so it should scale down well, probably be lighter too, might be that it don't have the torque and throttle range needed. 
It would be an shaft as you say with the two pumps and the generator. Sounds smarter to me. 

[StrandedonEarth]

Part of the plan is to capture heat to pressurize the tanks. I don't think a turbopump would like the kind of back pressure a decent heat exchanger would give. 

[passinglurker]

car engines in space are cool and all, but why not a fuel cell?

[PB666]

Its not a car engine, its like comparing a jet ski with a jet aircraft.

IC create power and motion, and pressure, FC create electrovoltaic pressure and power.

What do you need most?

Anyway, I wonder where this is going to go, I think its kind of nuts for a whole bunch of reasons.

 

 

[wumpus]

I had trouble following the reasoning (it may have been coming through multiple marketing/PR types), but it sounded like inefficiency was part of the goal (they needed high temperature exhaust, or possibly just a heat source).  Typically the benefit of an IC engine over a turbine is wider levels of semi-efficient power levels, not sure if they care about it here.

[Bill Phil]

On July 7, 2016 at 10:22 AM, p1t1o said:

I guess it must have some advantage over a very small turbopump? A turbopump strikes me as smaller, lighter, simpler (fewer moving parts, increases reliability and reduces friction losses?) and already space-tested, and would still have the water vapour "exhaust" for propellant settling, and the rotary power could do all the same things as an IC engine. 

Perhaps a turbopump doesn't scale downwards well? They make a big deal of "smoothness" in the article, perhaps this is a factor?

Turbopumps are pretty complex, let alone expensive. Many people have joked that a rocket is simply a turbopump with a nozzle attached. It can easily be over half the cost of a rocket engine.

[VaPaL]

@Bill Phil They are more complex and expensive to design, but as a component they are a lot more simpler. Less moving parts it's the big difference in the complexity, it's basic an axle spinning, seals and bearings. An IC engine, at least cars' IC engine, have a lot more moving parts. A think it will also be heavier. Ratation speed is another problem, is harder to achieve hight pressure/flow rate at lower speeds, to not say impossible

[kunok]

1 hour ago, VaPaL said:

They are more complex and expensive to design

And to manufacture. A piston is extremely simple to manufacture, a turbopump is a very difficult to do. Maybe the way is using a wankel IC engine

[VaPaL]

26 minutes ago, kunok said:

And to manufacture.

Not quite, I mean, the turbine wheel and the impeller are quite a pain to manufacture, but with additive manufacturing the impellers could be done kind off easily.

[kunok]

Just now, VaPaL said:

Not quite, I mean, the turbine wheel and the impeller are quite a pain to manufacture, but with additive manufacturing the impellers could be done kind off easily.

Well, that's not entirely true, additive manufacturing can help a little, but in reality it's only a substitute of the casting, you will need to machine it anyway to get in tolerances, it really doesn't have too many advantages in the case of the turbopump (also is an additive manufactured turbopump strong enough to overcome the huge forces involved? additive manufacturing produces porous materials with bad structure, better than casting but not that good). In the other hand, the nozzle with internal refrigeration channels and other structural parts takes a lot of advantage. And there is also the problem that IIRC, only Inconel718 is aerospace certificated to be used in additive manufacturing.

PD: it's late here and my english isn't flowing at all.

[SuperFastJellyfish]

44 minutes ago, kunok said:

Maybe the way is using a wankel IC engine

From the article:

Quote

The key engine requirement was to have a robust and simple design that would maximize use of commercial experience and off-the-shelf hardware. The design team traded high-performance configurations like the air-cooled Wankel, and decided that a liquid-cooled Inline 6 (I6) cylinder engine offered the best combination of weight, operating robustness, performance, heat rejection, redundancy and low vibration. Compared to the Wankel, it offered a well characterized lubrication system and had large areas for extracting waste heat via standard liquid cooling. Waste heat is used in IVF for propellant vaporization; the more available, the more robust the overall system design.

The best part, in my opinion, is the weight reduction of all the extra systems that it will replace.  The article says the engine will probably be less than 50kg. 

Quote

The basic design of the Generation 1 development engine is shown in Fig. 4 and Fig. 5. The IVF ICE only displaces 600cc with a compression ratio of 6.5 and a redline of 8000 RPM. Renderings and photographs of the engine are consistently misleading – the engine is amazingly small, at less than 700mm long, despite no effort to remove excess material. No effort was applied to shed mass from the Generation 1 engine but it is likely it will weigh less than 50kg in flight configuration.

 

[kunok]

1 minute ago, SuperFastJellyfish said:

From the article:

The best part, in my opinion, is the weight reduction of all the extra systems that it will replace.  The article says the engine will probably be less than 50kg. 

The "joke" (a bad one) is that wankel is a worse option probably because is a lot less developed, look at the "commercial experience and off-the-shelf hardware", is a shame, because properly developed it could have been a substitute of the actual alternative IC engines. Mazda (almost) alone can't compete with all the rest of the engine industries in research and developments.

[VaPaL]

@kunok There are additive methods where the material gets 90-95% of it's strength, and I think I read somewhere about one method that improves the strength, but don't quote me on that. The most "conventional" way of making an impeller is machining it in two parts and "welding" them together (don't recall the execly name in english, sorry). This produces tensions in the material that one has to get rid off and can cause some deformations. A more 'modern' way to do is by electric discharge machining (EDM).

Any way, there are studies about the possibility to use additive manufacturing on the impeller. For what I read it's viable.

The biggest problem here is the rotational speed, 8k rpm is to low, normally it goes up from a minimum of 30k.

Sorry for my english as well, not native and drinking some beer =P
 

[SuperFastJellyfish]

6 minutes ago, kunok said:

The "joke" (a bad one) is that wankel is a worse option probably because is a lot less developed, look at the "commercial experience and off-the-shelf hardware", is a shame, because properly developed it could have been a substitute of the actual alternative IC engines. Mazda (almost) alone can't compete with all the rest of the engine industries in research and developments.

Sorry, I missed the joke.  I've been drinking.    Cheers!

6 minutes ago, VaPaL said:

Sorry for my english as well, not native and drinking some beer =P

 

Right there with ya!  Happy friday!

Edited July 8, 2016 by SuperFastJellyfish

[VaPaL]

@SuperFastJellyfish Happy Friday! Cheers!! 

[Bill Phil]

3 hours ago, VaPaL said:

@Bill Phil They are more complex and expensive to design, but as a component they are a lot more simpler. Less moving parts it's the big difference in the complexity, it's basic an axle spinning, seals and bearings. An IC engine, at least cars' IC engine, have a lot more moving parts. A think it will also be heavier. Ratation speed is another problem, is harder to achieve hight pressure/flow rate at lower speeds, to not say impossible

Complexity has more things involved than just number of parts.

[VaPaL]

@Bill Phil I know, but we are talking about the final product, up and running, and a TPU is way simpler than a IC engine. (obs: I talking about the part itself, not the whole system).

[Bill Phil]

2 minutes ago, VaPaL said:

@Bill Phil I know, but we are talking about the final product, up and running, and a TPU is way simpler than a IC engine. (obs: I talking about the part itself, not the whole system).

I don't think they're planning on replacing the TPs.

[VaPaL]

11 minutes ago, Bill Phil said:

I don't think they're planning on replacing the TPs.

Yep! I misunderstood this image. I saw the H2/O2 pumps and a IC engine powering them and assumed that it was feeding the combustion chamber. 

 

 

 

[StrandedonEarth]

Turbopumps probably don't have the same torque as an ICE. Turbines take longer to spool up.

[magnemoe]

1 hour ago, StrandedonEarth said:

Turbopumps probably don't have the same torque as an ICE. Turbines take longer to spool up.

Probably also the fact that they are don't have much throttling, This might be important, stage heat up more in the sun and need more power before and during an burn.
 

[AlphaKerman]

https://en.m.wikipedia.org/wiki/Roush_Fenway_Racing

Who knows a racing team ever build engine for rockets huh? 

Nowadays a lot of innovation of rocket engine was put to rocket engine. If you could build it much better, why not? 

[Hydrothermalventclam]

Quote

That means exciting things like asteroid mining and other missions that require a lot of what space geeks call ‘delta-v,’ which is roughly translated as “moving around.”

This part made me laugh.

Also, I think that this is a good idea if they can actually do what they want to.