A way to generate power is within your grasp, but there is a catch or two

A theory is spinning up in my head. The theory is that convenience has rotted the brains of just about everyone. So everybody looks for the easy way out, and there isn't one.

Here's a way out. It means going back in time before the convenience rotted everybody's brain. Americans used to be more self-reliant. Now everybody wants somebody else to do it for them. This is what I call the convenience trap. It has a great risk of leading to a totalitarian society.

Anyway, the Amish didn't fall for it. But will the Amish survive if the nation goes totalitarian?

By the way, the Amish are self-reliant, but they aren't necessarily rugged individualists. They have cohesive communities. They have rules. Those who wish to stay have to follow the rules. Freedom might mean that you can break the rules, but not if you want to remain in a cohesive society.

Is there an easy solution to cleaning the contamination in the fuel supply for Starship?

10/16/26:

It appears that the speculation is wrong.

Speculation alert: A bit of persumption here, as the question probably answers itself. If there was an easy solution, SpaceX would be using it, yes?

10/7/26:

How to implement the idea? This idea differs from the AI discussion in that the contaminants are created. If they are created, then they must be removed. Is the removal feasible?

To answer that, I refer to the testing for the Skylon concept SSTO vehicle. It uses a pre-cooler that enables it to fly at hyper-sonic speeds. Although the Skylon has not flown, the pre-cooler has been tested and found feasible. Perhaps a device similar to the Skylon pre-cooler can take the carbon dioxide and water contaminants out of the oxygen mix coming off the pre-burner pumps? The pre-cooler from the Skylon can handle a lot of hot gasses, that's its job.

Besides, there's really not that much, about 2 tons according to the deep dive mentioned in an earlier post.

Perhaps the hot gases off the pre-burner can melt the ice and vaporize the dry ice so that they can be released?

That would imply a two-step process. First, freeze the mixture, then melt and dispose of it.

If it is two-steps, then that implies two devices or chambers. A freeze chamber, and a melt chamber.

Perhaps a mechanism can alternate between the two? A third chamber may need to hold gases from the pre-burner until a chamber is ready?

All this implies a level of complexity and control that SpaceX would rather avoid?

In that case, on chamber only, and it just freezes it until it can be disoposed of later.

10/6/26: The original post is below:

Anyway, not knowing any better, let's look at one possibility. First of all, SpaceX's contamination problem results in the icing problem that starves the engines for fuel. It's my guess that this is a large part of the reliability issues that the engine appears to have. Note that I use the word "appear". It isn't an engine problem per se, but a system problem.

The "system" uses the contaminant to maintain pressure in the tanks as they empty during flight. The contaminants come from the burning of the methane and the oxygen in the pre-burners that deliver fuel to the engines at high pressures. So there's some burning of the fuel, and it gets mixed into the tanks. The tanks are holding cryogenic fuels, so the contaminants will freeze and that's where the problems start.

Carbon dioxide is one of the contaminants, and it is the bigger of the two issues. Water ice floats on the liquid oxygen, but dry ice (frozen carbon dioxide) sinks. When it sinks, it can clog up the fuel intakes. No bueno.

The idea I had was to freeze it out of the exhaust BEFORE it gets injected into the oxygen tank. It is mostly oxygen, with the contaminants as mentioned. If the contaminants are frozen out, then there's no more contamination, right? But what to do with these contaminants?

Carbon dioxide (dry ice) can be vented off since when heated, it will revert to a gaseous state. Water ice will melt, but isn't a huge problem anyway if it refreezes.

How to heat it? It may not take much, as the freezing point is about 100 degrees below zero Farenheit. This is actually much warmer than the cryogenic oxygen.

All this may seem simple in concept, but there may be a catch. Or is there? That's what I'm not too sure of. Carbon dioxide will behave differently when under pressure. If you pressurize it, it may get a little tricky to handle.

In practice then, you would cool the exhaust from the pre-burners, using the cryogenic fuel as a means of cooling down to a solid state. Then you would have to obtain a heat source, perhaps from some return gas from another heat exchange in order to return the dry ice to a gaseous state, which can then be vented off.

Easier said than done, perhaps...

Water freezes at a relatively high temperature. Perhaps the water could be used to change the state of the dry ice to a gas.

Could this work? It probably would, but would it be worth it? It all depends on how much hardware you'd need in order to implement it.

There's a lot of heat exchanging going on, and maybe that would make it too complicated.

But this is just a speculation anyway.

Stuff's happening, no bumper sticker required

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.