How SpaceX Solved Superheavy's Major Fuel Contamination Problem

This is a deep-dive that may appear to be out of date. It may also have been blogged here or on the main blog. If it was blogged before, I cannot find it yet. So, at the risk of repeating myself, and since the Starship/Superheavy is still experiencing some troubles with engine outs, I theorize something here that may have been seemingly fixed, but hasn't been really fixed for good.

The possible issue here is the development of ice in the ship and booster, and this ice could be the reason for the engine failures.

Indeed, the AI was quizzed and seemed to deny that this is a problem, but I have an issue with that conclusion. To be sure, I haven't watched all of this deep dive as of this writing, but I think I've seen enough to make a post. So here it is: NOTE: AI dialogue not included, but may be added later...



Updated:

I watched the rest of the video, and I was still dissatisfied. Rather than ask the GAB AI, I asked the Brave AI. I was in luck. It turns out that I am most likely on the right track. It is not clear that the Starship system has done away with the problem altogether, or not. It appears from the Brave AI that they've probably not implemented the most likely permanent fix.

If so, I thought as much because I saw or heard somewhere about icing again. That's what made me come back to this CSI Starbase deep-dive to take another look.

Anyway, here's the Brave AI part that I saved for your perusal below:

## Autologous vs. Autogenous: The Distinction

The term **"autologous"** (as used by SpaceX engineers in CSI Starbase Q&As) refers specifically to the **clean-gas** variant of autogenous pressurization. The distinction:

| | **Autogenous** (current Starship) | **Autologous** (clean / proposed) |

|---|---|---|

| Gas source | Preburner exhaust | Dedicated heat exchanger on a propellant bleed |

| Gas composition | "Dirty" — O₂ + H₂O + CO₂ + trace CH₄ | **Pure** single-component (O₂ or CH₄) |

| Contamination | Icing, dissolution loss | None |

| Hardware | Tap-off valve from preburner | Dedicated heat exchanger + bleed line |



## How Autologous Pressurization Works

The mechanism is straightforward:

1. **Bleed**: A small flow of liquid propellant (O₂ or CH₄) is tapped from the turbopump discharge — the same high-pressure liquid that's already being pumped to the main injector.

2. **Heat exchanger**: That liquid passes through a **dedicated heat exchanger** that is thermally coupled to the engine's waste heat (typically the gas generator or turbine exhaust, or the regenerative cooling loop). The liquid absorbs enough heat to fully vaporize.

3. **Feed back**: The resulting **pure gaseous propellant** is routed back up into the ullage of the tank it came from.

The critical difference from the current "dirty" system: the gas **never contacts combustion products**. It's the same molecule that was in the tank, just in a different phase. No water, no CO₂, no unburned fuel.

## Historical Precedent: The Space Shuttle

The Space Shuttle External Tank used exactly this approach. After SSME ignition:

- A small bleed of LH₂ was taken from the turbopump, heated in a dedicated heat exchanger (warmed by the gas generator exhaust), and fed back as gaseous hydrogen into the LH₂ tank.

- A parallel bleed of LOX was heated and fed back as gaseous oxygen into the LOX tank.

This is the textbook autologous system — clean, single-component pressurant, no contamination.

## Why Starship Ditched It (For Now)

The Raptor 1/2 originally **did** have a heat exchanger for this purpose. SpaceX removed it in favor of the simpler preburner-exhaust tap because:

- One less heat exchanger = less mass, fewer parts, less thermal management

- The preburner exhaust is already at very high temperature (the O₂-rich preburner runs at ~1,500 °C), so it's an almost free heat source - The "dirty gas" problem (icing) was initially underestimated

The tradeoff is the contamination: water and CO₂ in the LOX tank cause ice formation on cold surfaces, and the pressurant gas dissolves into the liquid (a parasitic propellant loss).

## The Path Back

The CSI Starbase Q&A (referenced in community discussions) explicitly identified autologous pressurization as the fix:

> *"One solution would be autologous pressurization where they could heat the oxygen and methane separately instead of using combustion product to pressurize the tanks."*

For Raptor 3, the question is whether the **auxiliary cooling system** (ACS) — the additional heat exchanger surface added to handle the higher chamber temperatures — has enough thermal capacity to double as the autologous heat exchanger. If so, the engine can produce clean pressurant gas without adding a separate component. This would:

- Eliminate the icing problem entirely

- Eliminate pressurant dissolution losses

- Make the ullage gas safe to use as a **hot-gas thruster** propellant (pure O₂ or CH₄, rather than a reactive mixture)

- Enable **non-pumping mode** operation (pressure-fed burns) for Mars landing and in-space operations, where you can't spin up the turbopumps

It's not yet confirmed as a flight implementation, but it's the logical end-state for the system.

Amazing video

It begins with a discussion of Starship and Orion. Then it swerves into a rocket concept that was never pursued. It was a concept that I knew about, and once asked about on a written question to the Space Show. It is called the Sea Dragon. The Sea Dragon would've been so large that it would've dwarfed even the Starship. It was designed for 500 tons to orbit.

Such a design would've jumpstarted human presense in space.

It was described as somewhat "dreamy" on the Space Show. Now here it is again, said to be decades ahead of its time. Perhaps someday it will actually be attempted.

The video will be jipped to that portion of the video that discusses Sea Dragon.

DAMS system?

Is this for real? It seems to be the kind of configuration that I favored in an earlier post. No, it is the brainchild of an individual who may or may not be associated with SpaceX. Actually, I asked a series of questions of GAB AI, and posted it here not that long ago. The DAMS system won't work. But something like it might.

It uses "pods" to land on the moon, and to be recovered for return to the Earth. If you can carry a "pod" in a Starship, then it MIGHT work. The Starship will have to be like a tug. It wouldn't land on the moon. Just the pod, which can take off from the moon and meet the Starship in orbit.

Now THAT might work.

Starship Flight 14 is taking shape, but pad is empty

NASASpaceflight Youtube channel

SpaceX is in transition??? No more Falcon 9 flights? Starship will take over??

How to classify this video? That is to say, which blog should it go on--this one, or the main blog? I decided that it should go here, because these are still experimental. They are not operational as yet, therefore, there is a speculative quality about them. On the other hand, they are like current events, and therefore news. It could easily go on the main blog because the main blog is more like current events, and this one is more like futurism.

Does that mean the future has arrived??

Using gravitational lens to image exoplanets. What a concept!

How SpaceX is making America uncatchable

Here's somebody saying what I've been saying for the last 15 years.

Another example of saying it in a way in which people may LISTEN.

Are you sure you want to put Elon out of business? Only if you don't care about the people you represent. My question is this: Why would you support somebody who doesn't have your best interest in mind?

JP Aerospace tests their home-made submarine

7/12/26:

Here's a list of update videos that JP has made recently. Do not be discouraged that the one shown first is from 4 years ago. You need to scroll through the list to find the most recent one, which was just days ago.

Given that SpaceX wants to colonize Mars, these airships that JP builds could come in handy on Mars. The requirements to get to orbit from the Martian surface are much less. Maybe Mach 10 or 11 would get you from the surface to Mars orbit. That may be feasible for his airships on Mars.

In other words, another way to get back and forth between the surface and Mars orbit without having to use the Starship.

5/17/25: The original post follows below:

 

The video below was published just prior to a test of the sub...

... and afterwards a post on the blog about it. Not many details, but those may be forthcoming.

Ellie in Space, Flight 13 video

Good job.

SpaceX is betting its future on this

Farzad youtube



Comment:

The golden goose keeps laying the golden eggs, but some folks want to cook the goose because it is "too fat". But if you try to extract their essense from them, you kill the goose. Not real smart.

Starship catch simulations

There are more perspectives here than you can shake a stick at. Given that I watched the launch at a place either near or at what is being simulated, then a jip at that location would be interesting to compare to an actual launch.

Beats the hell out of this stupid political crap, does it not? But the stupid political crap is threatening the good stuff.

This looks like a cool YouTube Channel

7/3/26:

It's in the database.

6/29/26: The original post follows:

It is called Sourcery.  How the devil did I miss this one??? 

A quick tour of the page shows a professionally constructed site. It looks like she interviews a number of the top people in the Aerospace field. If I don't know it, I am gobsmacked. Which shouldn't be too hard.

I'm impressed.

Update a little bit later:

Here's Molly O'Shea interviewing Tom Mueller. O'Shea created this YouTube channel, and Mueller built the Merlin engine on the Falcon 9.

Type III Dyson Sphere of Highly Advanced Civilizations Around a Super Massive Black Hole

6/13/26:

Forget about all that. Look at this! Nobody can relate to highly advanced civilizations around a super massive black hole, but they sure can relate to massive amounts of money. Show me the money??? Yeah, lots and lots of it.



Jan 20, 2012:

Type III Dyson Sphere of Highly Advanced Civilizations Around a Super Massive Black Hole

The Rio Grande River does go to the Gulf

Or it appears to. There were some videos that said that the Rio gets used up before reaching the Gulf. Those videos are wrong, or the water is coming from somewhere else. That's cuz there's a River there, and there's water there. It's actually quite large.

I got a video of it that I will share eventually once I get around to it. I'm at Starbase Texas for the Launch ot Test Flight 12 of the Starship.

Anyway, got things to do, and maybe places to go. So that's all for now.

Here's a video I made

The launch video

Just got home and I am tired...

Anyway, here's a video I made of the launch of Flight 12. I actually got to see the darned thing blast off after all! One scrub is all it took...

The trip was long. It rained most of the way back. As you may notice just after the launch, that my reaction was a bit interesting. (at least I thought so.)

Booster 19 full static fire

5/13/26:

Schedule slips to 19th! Arghhh!

5/7/26:

Homing in on the next flight test. Maybe they'll 'light the candle' on the 15th.

Another explosion at Starbase

Angry Astronaut breaks down the latest mishap at Starbase. He likes to compare SLS with Starship. He admits that Starship has amazing tech, but focuses on all the growing pains for the new system.

But there are some disquieting things that keep happening with their system. You have to wonder if there's a major catastrophe around the corner with this thing.

Marcus House weekly video post (Starship 12 launch date)

Yours truly would love to be there at Starbase to see that sucker launch. But there's a problem... Maybe more than just one problem.

Faster than light speed

Maybe even ludicrous speed. Don't know about plaid.

SpaceX's Starship getting close to launch time

Problems with SpaceX's Raptor 3 engine?

It's been several months now since the last launch. Also, this is a brand new rocket on a brand new launch pad.

An "expensive hole in the ground" is a worrisome prospect. Hopefully, SpaceX has tested this thing six ways to Sunday, and back again.