Retrieving steam from Steam/hydrogen engine

[blash365]

I am planning to collect the exhaust steam of my hydrogen engine rocket to gererate even more hydrogen/oxygen from it.

Did anybody try to achieve a build yet and are there any results regarding volume and usability?

[FIXBUGFIXBUGFIX]

How will you condense steam?

I prefer morbs-->PO2-->puft-->slime-->PW-->water

[lee1026]

Yep, I tried it. It works extremely well. I did it in survival, so I don't have exact numbers for you, but I would estimate that I yield well over a ton of water per launch. I can't estimate whether you break even on the hydrogen alone if you throw away the oxygen, but as part of an integrated system, it makes oxygen nearly free.

 

A few notes: 

 

Hydrogen rockets run hot, really hot. You need a way to cool it to be able to extract useful steam out of it. I used a triple stack of steam turbines and it wasn't close to be able to keep up with regular launches. (yes, steam turbines can delete infinite heat, but with steel components to recycle water, I only can realistically delete heat from 250 or so down to 150) I shut down the rocket silo to build a 8 tall steam turbine so I will know how well that goes later.

 

Hydrogen exhaust WILL melt the pile of regolith on the floor of the silo to magna, which is a nice sustainable source of rocks (~2-4 ton per launch). You will want to raise a lot of hatches.

 

Condense the steam will require a lot of heat deletion, so pick your favorite method. If you run Petroleum rockets, you will have lots of CO2 to work with. Get a loop of Carbon scrubbers->water sieve set up, and pump the air from the rocket silo to the loop. Carbon scrubbers and water sieve both output at 40 degrees, so they will stabilize the area in temperature somewhat. If you cool the rocket silo to 500K via the steam turbine (energy positive!), you can stabilize roughly one (air) pipe of steam with one pipe of CO2.

[FIXBUGFIXBUGFIX]

21 minutes ago, lee1026 said:

down to 150

The output of steam turbine is always 150C (425K), so 8 tall turbine won't help you get colder steam.

[JohnFrancis]

36 minutes ago, blash365 said:

Did anybody try to achieve a build yet and are there any results regarding volume and usability?

I did build one in debug for proof of concept but nothing that could be realistically implemented. For volume you looking at roughly 1800KG. 750kg of water on take off and 1050kg on landing for both hydrogen and Steam. Petroleum does not generate steam. The amount of steam generated is not affected by quantity of fuel used, destination or rocket configuration. Steam rockets are much much cooler and quite viable for water capture, the amount of heat generated by hydrogen is insane. Side note you cannot "flood" a rocket, so you can fill the launch chamber with liquid (tested QoL1) to help with the cooling and it will not interfere with launch or landing. On the other hand that might cause the exhaust to infuse additional heat into the liquid increasing your cooling requirements. I never went past proof of concept when I realized how much heat I was going to have to deal with, it just looked like to far to much effort for to little return. Edit:  Here is the notes I made on it during a video tutorial, I remembered most of it correctly.

[lee1026]

8 Tall turbine will delete more 500K energy though, because the bottleneck in the system is condensation capacity. I can condense about 2kg/s and have to limit the hot area to about 250c for equipment safety reasons. That limits each layer to be deleting roughly 1.2million DTU/s. With 8 layers, that is 10 million DTU/s, which I am hoping will be enough (but then again, the three layer system is deleting roughly 3 million DTU/s and it isn't keeping up, but hey, at least I have infinite electricity now)

 

With the amount of energy that I am getting out of the rocket silo, I would say that it is worthwhile trying to harvest a hydrogen rocket's exhaust even if the only thing you are going to do with it is to generate power.

[Mullematsch]

I never understood why people stack steam turbines?

If cooling capacity would be the bottleneck, would having several turbines side by side not be superior?

 

[lee1026]

The bottleneck in my design is the ability to condense the steam. If I have several of them side by side, I have to condense several times more steam.

 

When I stack 8 of them, I get 8 rounds of heat deletion despite only condensing it once. Condensation is extremely expensive in terms of energy and resources (condensing just 2kg/s can require as much as 2 super coolant aquatuners in the worst case because the exhaust usually comes out at way higher than 425K because heat transfer through the turbine itself), so running a giant stack of steam turbines is the (only?) practical way to run an energy positive condensation steam turbine design.

 

The upside of a condensation steam turbine design is of course being able to stack the steam turbine sky high. Each layer requires 3kg of pressure than the last.  Because gas don't travel instantly from the output of one to the input of the next, you need about 5kg of pressure for each layer. That limits air pump designs to about 3 layers since the bottom is 20kg.  At the bottom of a condensation design, we are looking at a full ton of steam. each layer require 5kg, so in theory we can do ~200 layers. In other words, we can stack it as high as we want.

[blash365]

18 hours ago, JohnFrancis said:

Here is the notes I made on it during a video tutorial, I remembered most of it correctly.

Thanks a ton. Additional thumbs up for the australian 'cent (i assume).;)

 

So how would i go about with cooling the hydrogen engine exhaust? Super coolant evaporizes at ~430°C and the steam is ~1400°C hot.

So i would need a different cooling medium for the initial steam output.

[JohnFrancis]

34 minutes ago, blash365 said:

So how would i go about with cooling the hydrogen engine exhaust? Super coolant evaporizes at ~430°C and the steam is ~1400°C hot.

So i would need a different cooling medium for the initial steam output.

Place drywall in the background and run radiant pipes but not near the base of the rocket, closer to the top would be better as the rocket will be moving faster so less exposure to the exhaust. The super coolant in the pipes will chill the rising steam enough to condense it and it will fall to the floor of the launch chamber. I used a giant system for this but in theory it should work with a smaller system. Not sure if there is a better method but that is how I would approach it at least to start and see where the testing takes me.

[lee1026]

Wall the whole rocket silo in diamond. Put the hot chamber of the steam turbine next to it. The diamond walls will conduct the heat. Since we are farming the nearest planet for rocket exhaust, we will have plenty of diamonds to eventually retrofit much of the silo background with Tempshift Plates  

 

Steam turbine hot chambers will generate power (and rapidly delete heat) until it reaches 500k. At that point, you can open the doors to side chambers with steel air pumps to start pumping the exhaust out to somewhere they would be more useful. 

 

During the hotest phrase, use doors and pump’s own generated vacuum to protect it from harm.