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This is a deep-dive that may appear to be out of date.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.

The $600 tank that beats a $10k powerwall

9/30/26:

The author of the video says he made a mistake, and he made a corrective video to make up for it. You can find it on his channel in the videos section. It should also be said that it doesn't change the fact that it is a useful idea, but perhaps it isn't the end-all type of solution that it may appear to be with that first vid.

9/29/26: The original post is below:

This isn't friendly to Elon Musk. But I don't worship Elon Musk. I don't worship his enemies either. For me, when it makes sense do it. When it doesn't, then don't do it. Other folks may have other decision rules. You decide which to follow. I like mine better. Maybe you like yours better. To that i say, vive la differnce! At least you have the freedom to choose.

Rain in West Texas

9/27/26:

It still hasn't made its way through West Texas. The forecast doesn't show anything alarming ahead, so maybe this will pass by the area without much impact. Rainfall in the area doesn't appear to be anything to be alarmed about. Not yet, at least. Still watching it.

9/23/26: The orginal post is below:

Hurricane Polo needs to be watched. It looks like it could be a threat to the area in which I have land. But since nothing's out there but the jackrabbits, there's no property damage possible for moi.

It gives me the opportunity to take a few notes, which I have. Indeed, I got a link from the AI which can give me comprehensive information about rainfall in the region. So I've got that going for me, besides the jackrabbits.

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.

The Boring Company's "Insane" hyperloop concept

Have you noticed anything about Elon Musk's ideas and the way they are presented? It seems that the word "insane" keeps showing up in their titles.

The following video is an example of that. It has that word in its title, then it shows why the idea isn't so insane after all.

The original idea was insane, because it was too difficult to pull off. This concept is much more modest, and already has a track record. Not exactly insane, ya'll. Anyway, here's the video. The hyperloop is just one part of the video, by the way.

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.

Fusion energy isn't 30 years away anymore

It's no longer a joke, says this video.

One of the themes of this blog is the mastery of energy. If fusion energy is mastered, so many other things will begin to fall into place. Namely, the mastery of space. With fusion, space colonization becomes feasible. You can take your own sun along with you anywhere you go.

So I've studied various strategies to master fusion energy. There was Bussard's Polywell. Then there's Lerner's Focus Fusion. That's only two of the approaches. Many others are in this race.

This video mentions Helion. It seems to me that I've written about it before, or if not, I am aware of the company.

Here's the video. I haven't watched all of it yet, so I'll watch it before I post it.



Comment on what the rest of the video was about:

The narrator mentions other companies besides Helion. But he doesn't mention Lerner's company. Lerner's company is seeking to perfect an approach the video DOES mention. Funny that he didn't mention Lerner's company.

Is there a problem with Lerner's approach? Maybe. His approach isn't to go with the BIG MONEY. He went with the LITTLE MONEY. It's a people's plan. The trouble with that, as I've been mentioning, is that the people have become dull-witted. I don't necessarily agree with Lerner. It may be naive.

So, either I'm wrong about investing in Focus Fusion, or this narrator is right. Like all things, we will see. Lerner's approach may be wrong in that he doesn't want to go with the BIG MONEY. Or Lerner may be right about the approach, but wrong about the people. Too many dumb-asses.

Addendum:

I didn't read through Lerner's link, and I'm really sorry to have done so. What a total loon.

His ideas are a disaster.

But his machine might work. Or it might not. If his machine is anything like his politics, he will fail miserably. Oh, well. It wouldn't be the first mistake I've ever made. However, note that Lerner DEPENDS upon this free enterprise to make his plan meaningful. Does he have enough snap to understand what he is undermining with his stilly political nonsense?

He should stay out of politics and stick with science. What he suggests is socialism, which is HUGE mistake.

Video: How NASA Will Build The Artemis Moon Base

It's a plan alright, but all plans are subject to that little something called uncertainty. None of this is certain. HOWEVER, if there is a will to do this in spite of the difficulties, then one thing IS certain. They will succeed.

The missing ingredient is this: Is there a will to do it?

It seems highly doubtful to me. Since this plan came from the Trump administration, a will a Democrat administration follow it? Don't bet on it. It hasn't been happening in recent history. Every change of party leads to a change in NASA priorities.

Making a homemade refrigerator that runs on fire

..cools down to 18 C. (about zero Farenheit)

A question is this: what practical use would this device have?

I can think of possibilities. However, for this to be practical, you'd have to know just how much cooling in terms of BTU, can be expected.

A clue is that he uses a 12 oz. soda to show that it can cool it down (for a summer day).

Cooling down one soda at a time doesn't sound like much.

Starship Flight 14 is taking shape, but pad is empty

NASASpaceflight Youtube channel