New ‘Autophage’ Engine Would Eat Its Rocket’s Body For Fuel

An international team of researchers has developed and tested a “self-eating” engine which would consume the structure of its rocket to launch small satellites, aka CubeSats, at a lesser cost and won’t add to the pressing problem of space debris.

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Tau.Neutrino said:

New ‘Autophage’ Engine Would Eat Its Rocket’s Body For Fuel

An international team of researchers has developed and tested a “self-eating” engine which would consume the structure of its rocket to launch small satellites, aka CubeSats, at a lesser cost and won’t add to the pressing problem of space debris.

more…

Hmm, not impossible perhaps because alumimium and plastics can be used as rocket fuel, and because common solid fuels can be made into rocket bodies. But there is a big problem with both of those. How do you contain the pressure?

> as the vehicle climbed the engine would work its way up, consuming the body from base to tip.

The nozzle shape would be unstable. Resulting in suboptimal thrust.

Unless the nozzle was a separate component that slid up as the fuel burnt up. Oh, that’s exactly what they plan to do. But then the problem of retaining the pressure remains. The rocket would still need an outer casing attached to the nozzle to retain the pressure.

Hmm, it might work, but would it be better?

I note that here the solid fuel is burnt in “end burning” mode. No off the shelf hobby rocket burns in end burning mode. End burning gives less thrust over a longer time than conventional solid fuel burning, which makes it useless as a first stage but bloody good as a second stage.

The purpose of the first stage (for an unmanned vehicle) is maximum thrust to get the rocket up to a speed where air drag becomes a problem. The purpose of the second stage is to hold a low thrust for a long enough time to get out of the atmosphere. A gun barrel or rail gun can substitute for first stage.

End burning of solid fuel can be done without autophage.

mollwollfumble said:

Tau.Neutrino said:

New ‘Autophage’ Engine Would Eat Its Rocket’s Body For Fuel

An international team of researchers has developed and tested a “self-eating” engine which would consume the structure of its rocket to launch small satellites, aka CubeSats, at a lesser cost and won’t add to the pressing problem of space debris.

more…

Hmm, not impossible perhaps because alumimium and plastics can be used as rocket fuel, and because common solid fuels can be made into rocket bodies. But there is a big problem with both of those. How do you contain the pressure?

> as the vehicle climbed the engine would work its way up, consuming the body from base to tip.

The nozzle shape would be unstable. Resulting in suboptimal thrust.

Unless the nozzle was a separate component that slid up as the fuel burnt up. Oh, that’s exactly what they plan to do. But then the problem of retaining the pressure remains. The rocket would still need an outer casing attached to the nozzle to retain the pressure.

Hmm, it might work, but would it be better?

I note that here the solid fuel is burnt in “end burning” mode. No off the shelf hobby rocket burns in end burning mode. End burning gives less thrust over a longer time than conventional solid fuel burning, which makes it useless as a first stage but bloody good as a second stage.

The purpose of the first stage (for an unmanned vehicle) is maximum thrust to get the rocket up to a speed where air drag becomes a problem. The purpose of the second stage is to hold a low thrust for a long enough time to get out of the atmosphere. A gun barrel or rail gun can substitute for first stage.

End burning of solid fuel can be done without autophage.

Why dont they use a rail gun to get rockets up to speed then fire the rockets ?

Tau.Neutrino said:

Why dont they use a rail gun to get rockets up to speed then fire the rockets ?

I think it would work. Similar to what was proposed by Jules Verne and by Robert Heinlein.

mollwollfumble said:

Tau.Neutrino said:

Why dont they use a rail gun to get rockets up to speed then fire the rockets ?

I think it would work. Similar to what was proposed by Jules Verne and by Robert Heinlein.

Wasn’t that the method used in The Moon Is A Harsh Mistress

Cymek said:

mollwollfumble said:

Tau.Neutrino said:

Why dont they use a rail gun to get rockets up to speed then fire the rockets ?

I think it would work. Similar to what was proposed by Jules Verne and by Robert Heinlein.

Wasn’t that the method used in The Moon Is A Harsh Mistress

Well spotted. Yes, that’s what I was thinking of.

mollwollfumble said:

Cymek said:

mollwollfumble said:

I think it would work. Similar to what was proposed by Jules Verne and by Robert Heinlein.

Wasn’t that the method used in The Moon Is A Harsh Mistress

Well spotted. Yes, that’s what I was thinking of.

In The Millenial Project, a serious semi-scientific book suggesting ways to get humans off this rock, the railgun was to be under the Serengeti for 4km to gain speed, then up the inside of Mt Kilimanjaro; the entire path was to be vacuum or very low pressure, with a membrane the spacecraft punctured as it entered the Earth’s atmosphere. The idea behind the long rail was to keep the acceleration to within the limits of human endurance whilst getting the craft moving sufficiently fast to leave the atmosphere without burning any fuel. The craft was to have water ice at the trailing end, which would be evaporated by high-power ground-based lasers at the top of Kilimanjaro to provide further thrust as needed.

btm said:

mollwollfumble said:

Cymek said:

Wasn’t that the method used in The Moon Is A Harsh Mistress

Well spotted. Yes, that’s what I was thinking of.

In The Millenial Project, a serious semi-scientific book suggesting ways to get humans off this rock, the railgun was to be under the Serengeti for 4km to gain speed, then up the inside of Mt Kilimanjaro; the entire path was to be vacuum or very low pressure, with a membrane the spacecraft punctured as it entered the Earth’s atmosphere. The idea behind the long rail was to keep the acceleration to within the limits of human endurance whilst getting the craft moving sufficiently fast to leave the atmosphere without burning any fuel. The craft was to have water ice at the trailing end, which would be evaporated by high-power ground-based lasers at the top of Kilimanjaro to provide further thrust as needed.

We should get Musk’s Boring Company onto the job straight away then.

btm said:

mollwollfumble said:

Cymek said:

Wasn’t that the method used in The Moon Is A Harsh Mistress

Well spotted. Yes, that’s what I was thinking of.

In The Millenial Project, a serious semi-scientific book suggesting ways to get humans off this rock, the railgun was to be under the Serengeti for 4km to gain speed, then up the inside of Mt Kilimanjaro; the entire path was to be vacuum or very low pressure, with a membrane the spacecraft punctured as it entered the Earth’s atmosphere. The idea behind the long rail was to keep the acceleration to within the limits of human endurance whilst getting the craft moving sufficiently fast to leave the atmosphere without burning any fuel. The craft was to have water ice at the trailing end, which would be evaporated by high-power ground-based lasers at the top of Kilimanjaro to provide further thrust as needed.

damn, i thought it was a project to put all the millennials into a rocket and blast them off into space!

JudgeMental said:

btm said:

mollwollfumble said:

Well spotted. Yes, that’s what I was thinking of.

In The Millenial Project, a serious semi-scientific book suggesting ways to get humans off this rock, the railgun was to be under the Serengeti for 4km to gain speed, then up the inside of Mt Kilimanjaro; the entire path was to be vacuum or very low pressure, with a membrane the spacecraft punctured as it entered the Earth’s atmosphere. The idea behind the long rail was to keep the acceleration to within the limits of human endurance whilst getting the craft moving sufficiently fast to leave the atmosphere without burning any fuel. The craft was to have water ice at the trailing end, which would be evaporated by high-power ground-based lasers at the top of Kilimanjaro to provide further thrust as needed.

damn, i thought it was a project to put all the millennials into a rocket and blast them off into space!

Like colonial transportation, I think that would be the wrong approach. We should move everybody else off to a brand new clean and shiny planet and leave the undesirables behind.

sibeen said:

btm said:

mollwollfumble said:

Well spotted. Yes, that’s what I was thinking of.

In The Millenial Project, a serious semi-scientific book suggesting ways to get humans off this rock, the railgun was to be under the Serengeti for 4km to gain speed, then up the inside of Mt Kilimanjaro; the entire path was to be vacuum or very low pressure, with a membrane the spacecraft punctured as it entered the Earth’s atmosphere. The idea behind the long rail was to keep the acceleration to within the limits of human endurance whilst getting the craft moving sufficiently fast to leave the atmosphere without burning any fuel. The craft was to have water ice at the trailing end, which would be evaporated by high-power ground-based lasers at the top of Kilimanjaro to provide further thrust as needed.

We should get Musk’s Boring Company onto the job straight away then.

It’s a bit tougher than that. Better to start with an unmanned version for lifting rockets that fire to put cubesats into orbit. That way the acceleration can be more and the weight less, so the length of rail is much shorter, making it easier to build.

I also keep thinking of the Mythbusters vacuum tube for accelerating a pingpong ball to supersonic speed.

btm said:

mollwollfumble said:

Cymek said:

Wasn’t that the method used in The Moon Is A Harsh Mistress

Well spotted. Yes, that’s what I was thinking of.

In The Millenial Project, a serious semi-scientific book suggesting ways to get humans off this rock, the railgun was to be under the Serengeti for 4km to gain speed, then up the inside of Mt Kilimanjaro; the entire path was to be vacuum or very low pressure, with a membrane the spacecraft punctured as it entered the Earth’s atmosphere. The idea behind the long rail was to keep the acceleration to within the limits of human endurance whilst getting the craft moving sufficiently fast to leave the atmosphere without burning any fuel. The craft was to have water ice at the trailing end, which would be evaporated by high-power ground-based lasers at the top of Kilimanjaro to provide further thrust as needed.

Gosh, there’s some serious geologic structure between the Serengeti and Mt Kilimanjaro. Much of the East African Rift. I doubt any tunnel would last long through that major and very active fault zone.

sibeen said:

btm said:

mollwollfumble said:

Well spotted. Yes, that’s what I was thinking of.

In The Millenial Project, a serious semi-scientific book suggesting ways to get humans off this rock, the railgun was to be under the Serengeti for 4km to gain speed, then up the inside of Mt Kilimanjaro; the entire path was to be vacuum or very low pressure, with a membrane the spacecraft punctured as it entered the Earth’s atmosphere. The idea behind the long rail was to keep the acceleration to within the limits of human endurance whilst getting the craft moving sufficiently fast to leave the atmosphere without burning any fuel. The craft was to have water ice at the trailing end, which would be evaporated by high-power ground-based lasers at the top of Kilimanjaro to provide further thrust as needed.

We should get Musk’s Boring Company onto the job straight away then.

I agree. The result would be anything other than boring.