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Comment by onetimeuse92304 | Hacker News Reader

Cute, but what is the point of this?

At the very best it could stop SSTO to orbit suck so much. But it seems SpaceX is far enough that it is not possible to get close to the efficiency with an autophage rocket. It maybe was possible as long as first stage was always destined to crash, but when it can land safely the entire efficiency equation got turned on its head.

Would that kind of rocket be usable for deep space (basically -- improve thrust to weight by eliminating the weight of the fuselage as you thrust)? I also don't think so. For space, much higher specific impulse engines exist than any kind of fuselage material that can burn itself.

So I just don't see any use of this.

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The point is simple.

The delta-V per rocket stage is governed by the Tsiolkovsky equation:

dv = Isp * g0 * ln(m_start/m_end)

So, if m_end goes to zero, you get a significant dv gain.

It has absolutely nothing to do with the "efficiency" of returning a stage or not.

Your comment is needlessly dismissive about a benchtop experiment that doesn't really compare to something like Starship and the engines that it uses.

This is really neat. It doesn't have to be groundbreaking to be really cool, but who knows maybe one day it will be.

Indeed many (most?) technology breakthroughs and great products start as "garage" experiments.

- Aviation didn't start with someone rolling out a 747, it started with the Wright Flyer - something that barely flew with just the right winds.

- Apple, Inc. literally started in a garage with an 8-bit computer with 8k ram and you had to provide your own case and power supply, monitor, and keyboard.

- The early stages of modern rocket technology looked not much different than this experiment: Here's a video of Goddard testing at his Aunt's farm:

https://upload.wikimedia.org/wikipedia/commons/transcoded/a/...

> "The neighbors complained"

http://www.zenpencils.com/comic/64-robert-h-goddard-the-rock...

From the paper's abstract:

> This both increases the maximum payload mass of a launch system and allows for the miniaturization of launch vehicles so they may be used as nano-launchers for the rapid access of small satellites to low-earth orbit.

Sounds great for weapons applications. :-/ Small tube which can reach as far as orbit.

Re-usabilitity is "not needed".

Might be useful in a Mars sample return sort of scenario.

As I said, it reduces problems of SSTO (Single Stage To Orbit). The problem of SSTO is low payload mass to the size of the rocket and fuel necessary to transport it. The main solution to this is having multiple stages. Which comes with its own problems -- multiple engines, complexity, more points of failure, etc.

But in the meantime SpaceX learned to reuse the stages so suddenly the problems are no longer as much of a problem as they were before.

> Cute, but what is the point of this?

There isn't much point. I don't know an application where other approaches wouldn't be superior.

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