[master_crab]

For all the talk of SpaceX and a new race to Mars, no one seems to remark on the fact that rockets haven’t remarkably changed much since Goddard’s day.

I remember asking one of my profs in college (an early researcher of the ramjet) what’s holding jet and rocket technology back. He said: melting point temps.

[WalterBright]

Haven't changed since Goddard? Oh my! Here's a list of the innovations the Germans made to Goddard engines in order to scale them up for the V2:

1. turbo-pump

2. building a jacket into the nozzle to both cool the nozzle and pre-heat the fuel

3. putting tiny holes in the jacket so the leaking fuel would form a boundary layer that would protect the nozzle from heat

4. baffles in the combustion chamber to damp out pogo-ing

There's a picture of Goddard looking at a captured V2 engine with his mouth hanging open in astonishment.

The Saturn V engines were scaled up V2 engines.

[avmich]

> The Saturn V engines were scaled up V2 engines.

That's very debatable :) - everything is everything else, if squinting hard enough. Just an injector head of F-1 was a serious R&D topic, with whole methods of experiments invented.

[WalterBright]

Obviously there was a lot of refinement and development going on in those engines.

For another example, the Ohain axial flow turbojet is quite recognizable even up to modern jet engines. The Whittle radial flow turbojet was a dead end.

Innovations 1..3 are all revolutionary, not evolutionary, advances in rocket engines. 4 maybe is.

https://airandspace.si.edu/collection-objects/v-2-rocket-eng...

The Saturn V engines needed much more powerful turbopumps, and so used a secondary rocket engine just to drive the pump. How cool can you get?

[panick21_]

> The Saturn V engines were scaled up V2 engines.

I mean, not really. They were a totally different cycle type. Different fuel. Different way adjusting trajectory. Different injectors.

Seems pretty different to me.

[WalterBright]

Different cycle type? I'm interested - what's different?

[panick21_]

I mean one uses the main propellant to drive the turbine the other has a sodium permanganate/hydrogen peroxide. That seems to me a pretty significant difference in how the engine works.

To be fair, technically one could call both gas generators but its still significantly different.

[WalterBright]

I'm sorry, but picking a different source of hot gas to drive the turbopump is not a conceptual difference. Just like adding nitrous injection to your car doesn't make it a conceptually different engine.

[panick21_]

Well, they are all chemical engines. We have no chemical engines that would work well for launching.

In space we do use a lot of solar electric propulsion and lots other things that Goddard knew nothing about.

Nuclear thermal propulsion could potentially be used but that has a whole host of issues where its not clear that its actually worth it compared to chemical.

SpaceX Raptor is approaching pretty much the peak of what is doable with chemical and if its fully and rapidly reusable it can bring the price to orbit down.

What really matters is not what method you use, but how much does it cost to go to orbit, or from LEO to Mars. From that perspective something like Starship is on a totally different level then anything that came before.

[master_crab]

“Well, they are all chemical engines. We have no chemical engines that would work well for launching.”

I mean that’s what chemical engines are for. You aren’t launching off the ground with any of the electric based systems, and accidental radiation concerns have always hobbled nuclear engines.

But, yes point taken on using them outside the atmosphere. However, they don’t improve our ability to launch manned missions greatly (at least not for the foreseeable decades).

[Robotbeat]

> You aren’t launching off the ground with any of the electric based systems

Well… https://www.spinlaunch.com/