Jump to content

SpaceX Discussion Thread


Skylon

Recommended Posts

5 hours ago, Spaceman.Spiff said:

Also, spaceX is producing its own fuel from CO2 in the atmosphere. It might not be carbon neutral, but it’s better than using fossil fuels.  

This is totally not true.

Musk has declared that he *intends* to do this, but it's thermodynamically crazy. Even though there is too much CO2 in the air right now, it's still only 400 parts per million. Just collecting it from the air is quite difficult. And then turning it into fuel NECESSARILY requires more energy than burning that fuel (second law, entropy), so it takes a crazy amount of energy to turn large quantities of CO2 into a hydrocarbon fuel.

And all that energy has to come from somewhere. Even if Musk has a huge solar plant that creates enough energy to make rocket fuel with, that's still energy that's not being used to avoid emissions in other places. Low-carbon energy should be used preferentially to replace high-carbon energy, not wastefully to try to turn CO2 back into methane.

Link to comment
Share on other sites

1 hour ago, kerbiloid said:

But the Big Dumb Boosters were using Big Dumb Engines.

The Big Dumb Boosters were intended to use simple, low-cost engines with a low part count.

There were several attempts at designing such an engine but the ones that got furthest along were the hydrolox TR-106 and the kerolox TR-107. They used an oxygen-rich staged combustion cycle but with lower performance (the TR-107 had only 66% the chamber pressure of an RD-180), allowing it to be easier to build while still being reliable. They used pintle injectors for throttleability and simplicity, and they used an ablative combustion chamber. When they were test-firing it, they found they could simply swap out the ablative combustion chamber liner on the test stand and refire without needing to replace any of the parts because the whole thing was relatively simple. 

Another Big Dumb Booster engine design was Fastrac, which also used an ablative liner but had a simple single-shaft, dual-impeller turbopump built by Barber Nichols operated by a kerolox gas generator. It used a hypergolic liquid igniter for startup simplicity and also used a pintle injector.

Tom Mueller was the project manager for the TR-106 and the TR-107, and the original Merlin 1A turbopump was built by Barber Nichols. The Merlin uses a pintle injector and ever since the Merlin 1B has used hypergolic liquid ignition. The original Merlin 1A also used ablative cooling but it was upgraded to regenerative cooling by the Merlin 1C.

And so SpaceX ended up with an engine that could be easily refired and could be repeatedly upgraded to squeeze out more and more performance, enabling the evolution from the original Falcon 9 to the Falcon 9 Block 5.

Edited by sevenperforce
Link to comment
Share on other sites

SpaceX seems to be experimenting with extracting propellants from the air, but I don;t think they have actually collected much (if any). I wonder if it is primarily LOX they are after, as well.

 

Link to comment
Share on other sites

7 minutes ago, tater said:

SpaceX seems to be experimenting with extracting propellants from the air, but I don;t think they have actually collected much (if any). I wonder if it is primarily LOX they are after, as well.

They have two goals here:

  1. work on technologies for ISRU on Mars
  2. greenwashing
Link to comment
Share on other sites

19 minutes ago, SOXBLOX said:

Is this a term for eco-advertising? Cause if it is, I like it.

I believe it's a term for companies doing a highly publicized "green" stunt to make the public think they are a green company while not actually being a green company. It is a term with negative connotations.

Link to comment
Share on other sites

57 minutes ago, Ultimate Steve said:

I believe it's a term for companies doing a highly publicized "green" stunt to make the public think they are a green company while not actually being a green company. It is a term with negative connotations.

Yup. It's definitely a pejorative term.

Link to comment
Share on other sites

Longer term, local production of lox would be useful as it is 80% of propellant mass.

For their notion of operations. 

loads of flights, Mars, etc.

Not saying it’s actually likely, but thinking ahead, it’s a possible issue since otherwise props are delivered by semis, and they need 1000s of tons per launch. Course how much they could extract might be noise compared to that.

Link to comment
Share on other sites

1 hour ago, tater said:

Longer term, local production of lox would be useful as it is 80% of propellant mass.

For their notion of operations. 

loads of flights, Mars, etc.

Not saying it’s actually likely, but thinking ahead, it’s a possible issue since otherwise props are delivered by semis, and they need 1000s of tons per launch. Course how much they could extract might be noise compared to that.

A LOX plant is just a big compressor plus a fractional distillation column, right?

The thing is, oxygen is 210000 ppm in the atmosphere. CO2 is 400 ppm. It's a lot tougher to suck the CO2 out of the air than it is to get the oxygen.

Link to comment
Share on other sites

1 minute ago, mikegarrison said:

The thing is, oxygen is 210000 ppm in the atmosphere. CO2 is 400 ppm. It's a lot tougher to suck the CO2 out of the air than it is to get the oxygen.

Yeah, that's why I don't think they are going for the carbon.

Again, I doubt it makes a huge difference for test level operations, but if they start launching a lot (because, you know, Mars demands it ;) ), then keeping those GSE tanks full is a lot of trucks. They're right on the water, but not anyplace where sea delivery is a thing, so it's all road traffic.

Dunno, seems like it might at least be a possibility. LOX is apparently pretty cheap, so maybe making their own is not that expensive.

Link to comment
Share on other sites

7 minutes ago, tater said:

Yeah, that's why I don't think they are going for the carbon.

They *say* they are going for the carbon. Musk announced some sort of prize for anyone who can build an atmosphere-to-fuel CO2 removal process and scale it up to reasonable quantities. But I think it's a pipe dream and a PR move.

https://www.xprize.org/prizes/elonmusk

Edit: Apparently the prize is for CO2 sequestration, which, while difficult, is certainly easier than CO2-to-fuel. You essentially have to do CO2 sequestration before you can do CO2-to-fuel anyway. Also, this appears to be a Musk thing rather than a SpaceX thing.

Edited by mikegarrison
Link to comment
Share on other sites

23 minutes ago, mikegarrison said:

The thing is, oxygen is 210000 ppm in the atmosphere. CO2 is 400 ppm. It's a lot tougher to suck the CO2 out of the air than it is to get the oxygen.

Hmm, but as long as they're separating the oxygen, it can't be that much harder to stash the CO2 for future use while they're at it, can it?

Link to comment
Share on other sites

29 minutes ago, StrandedonEarth said:

Hmm, but as long as they're separating the oxygen, it can't be that much harder to stash the CO2 for future use while they're at it, can it?

If all they had to work with was CO2, then yes, but if you want LOX, no need to crack the O2 off the CO2, there's free oxygen around, lol.

I thought someone at SpaceX had said that the offshore facilities might have the capability to make propellants partially from a logistical standpoint.

Link to comment
Share on other sites

5 minutes ago, tater said:
36 minutes ago, StrandedonEarth said:

 

If all they had to work with was CO2, then yes, but if you want LOX, no need to

I was thinking more along the lines of as long as they’re separating the 20% oxygen, they could separate the 400ppm of CO2 too, and stockpile it for future use or storage/sequestration 

Link to comment
Share on other sites

18 minutes ago, StrandedonEarth said:

I was thinking more along the lines of as long as they’re separating the 20% oxygen, they could separate the 400ppm of CO2 too, and stockpile it for future use or storage/sequestration 

It takes less energy to distill CO2 than O2. It takes a LOT more energy to crack CO2 and H2O into O2 and CH4 than it does to just distill O2 out of thin air. 

Link to comment
Share on other sites

7 hours ago, mikegarrison said:

The FAA does not approve EISs. Do you mean the EPA?

EIS is more than just environment environment. Much the same that FRA reviews railway EIS, FAA reviews air-related EIS.

Link to comment
Share on other sites

5 minutes ago, YNM said:

EIS is more than just environment environment. Much the same that FRA reviews railway EIS, FAA reviews air-related EIS.

I don't believe this is true.

And it's not supported by the link you yourself provided.

Quote

In compliance with the National Environmental Policy Act (NEPA), the Federal Aviation Administration (FAA) Office of Commercial Space Transportation prepared an Environmental Impact Statement (EIS) to evaluate the potential environmental impacts that may result from the FAA proposal to issue launch licenses and/or experimental permits to Space Exploration Technologies Corp.

The FAA has submitted the Final EIS to the U.S. Environmental Protection Agency (EPA).

It's clear here that the FAA *prepared* the EIS, not that they approved it. They then sent the EIS to the EPA, which was the agency that had to approve it it (or not).

Edited by mikegarrison
Link to comment
Share on other sites

1 hour ago, mikegarrison said:

I don't believe this is true.

And it's not supported by the link you yourself provided.

OK yeah probably since Boca Chica is a reserve under the NPS.

But for other stuff normally FAA has the final word. The Record of Decision for Boca Chica is signed fully in FAA's power and the accompanying programmatic agreement with other related agencies' power (in Boca Chica's case it was Texas State Historic Preservation, National Park Service and Advisory Council on Historic Preservation). EPA is barely involved - US Fish and Wildlife Service is under the Department of the Interior. EPA probably only keeps a copy of everything but that's about it.

This map is interesting though :

Spoiler

unknown.png

unknown.png

Interesting to note it just ends on the border...

 

Edited by YNM
Link to comment
Share on other sites

19 minutes ago, YNM said:

Ok yeah probably since Boca Chica is a reserve.

But for other stuff normally FAA has the final word. The Record of Decision is signed fully in FAA's and other related agencies' power.

Interesting reading. It does appear that the FAA both prepared and accepted that O'Hare EIS you reference. Apparently this serves as a record that they followed the required process. Though they did coordinate with other agencies, including the USEPA.

Link to comment
Share on other sites

4 hours ago, StrandedonEarth said:

I was thinking more along the lines of as long as they’re separating the 20% oxygen, they could separate the 400ppm of CO2 too, and stockpile it for future use or storage/sequestration 

I see what you are saying there, but just separating out the oxygen doesn't mean you get all the other components of the atmosphere for free.

(OK, I looked this up on the web. You do indeed run the air through an iterated process of fractional distillation. They can separate it out into oxygen, nitrogen, and argon. I would guess they could pull out other trace gasses too, which would include CO2, but the point is that you would have to process a whole lot of air to get very little CO2. I think commercial CO2 is actually made by oxidizing natural gas and other hydrocarbon fuels.)

Link to comment
Share on other sites

Well I reckon someone is going to have to come up with a way to do large scale carbon removal at some point. And I think whoever comes up with a way of doing so efficiently is going to make a lot of money in future getting paid to do so by governments.

Personally I think extracting it from sea water might be the way to go, as it's easier to process large masses of water than air.

If Musk wants to learn how to do it to produce rocket fuel I'm all for.

Link to comment
Share on other sites

I guess instead of using a cryogenic procedure it would be easier to sequester carbon dioxide chemically as carbonates. It might be as simple as bubbling air through a large vat of dissolved sodium or ammonium hydroxide, then dissociate the carbonate by heating where and when you need it. Since the sabatier reaction is exothermic and needs to run pretty hot, there might be some nice synergies you might be able to use as well.

Link to comment
Share on other sites

3 hours ago, Piscator said:

I guess instead of using a cryogenic procedure it would be easier to sequester carbon dioxide chemically as carbonates. It might be as simple as bubbling air through a large vat of dissolved sodium or ammonium hydroxide, then dissociate the carbonate by heating where and when you need it. Since the sabatier reaction is exothermic and needs to run pretty hot, there might be some nice synergies you might be able to use as well.

If you can work out how to do it in conjunction with nuclear energy production - as part of an efficient cooling process, let me know.  I want in early. 

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...