Rotary Motion to Linear Motion - Thermal Activity to Rocket Thrust

tahanson43206 · 2023-10-02 07:00:28

In recent discussion with ChatGPT(4), I have been made aware that a device that converts rotary motion to random motion offers a way to convert electrical energy to thrust in a rocket. An example that is readily available for study is the SpinLaunch system, which currently has achieved an altitude of (about) 40 miles, using a rotary launch system.

The insight I received from conversation with ChatGPT is that the size of the rotary to linear motion converter does not have to be as large as the SpinLaunch system to be useful.

On Earth, humans have developed a remarkable array of centrifuges of various sized and capabilities for medical, commercial and military use.

At the top end of the scale are Ultracentrifuges, which are reported to have rotation rates on the order of 1,000,000 RPM. A much more typical rotation rate is 100,000 RPM with an arm length of 11 centimeters. I have requested more information from the manufacture of one of these devices, and will report if there is a response.

In traditional propulsion using chemicals, random motion of thermally active molecules is converted to linear motion by guiding some of the molecules in a chamber to a carefully shaped exit. The consequence of the design of this exit is that the departing molecules exert pressure on the flanges outside the exit port, and this pressure is communicated back to the space craft (or rocket on Earth) through the metal structure. Ultimately the pressure is communicated electrically to all the molecules making up the space craft, and the entire collection of molecules moves in a direction opposite to that of the exiting molecules.

However, it appears that the best ISP that can be achieved using chemicals is about 450. This is a number that humans have found they can work with, and the US Space Shuttle made multiple flights to space using this system. The purpose of this topic is to investigate and report upon the use of rotary motion as a way to reach higher ISP while at the same time, achieving significant levels of thrust.

Competing systems use linear accelerators to achieve high ISP. Examples are ion accelerators, of which there are by now a great variety. As of this date in 2023, none of these systems achieve significant thrust, although all achieve impressive ISP levels. The purpose of this topic is to explore the possibility that using rotary motion to impart linear motion to molecules might prove able to deliver linear motion to a sufficient number of molecules so that thrust imparted to the space craft is significant.

(th)

tahanson43206 · 2023-10-02 07:12:35

To my knowedge, the NewMars forum is fortunate to have in residence at least one of:

1) Aerospace engineer
2) Mechanical engineer
3) Electrical engineer

We may have a nuclear engineer, and that would be welcome if it is the case, because the problem at hand is to find the best possible way to enlist the thermal output of a nuclear fission reactor to provide thrust for a very large space craft.

Thermal energy, by it's nature, is a random process. Molecules in the vicinity of an active nuclear fission process are given energy to bounce against each other, and the energy thus produced can be bled off to perform useful work. It appears that the efficiency of this process can be as high as 33%, in production of electrical energy that might be used for space craft propulsion. That means that 67% of the thermal energy is wasted, unless a way can be found to employ it for some useful purpose, such as heating the interior of the space craft.

In the NERVA nuclear rocket, the random motion of hydrogen molecules is increased by nuclear fission processes, so that an ISP of (on the order of) 900 has been reported. In this case, the random motion of the hydrogen molecules is directed through an exit, appropriately shaped to facilitate conversion of the random motion of the molecules to linear motion of the rocket vehicle in the opposite direction.

The purpose of ** this ** topic is to explore the use of rotary-to-linear motion conversion devices to exceed 900 ISP (or at least meet that level) while at the same time delivering comparable thrust.

This machinery is the province of the Mechanical Engineer.

Because the machinery is powered by electricity, it is simultaneously the province of the Electrical Engineer.

Because the purpose of the machinery is to deliver linear motion to a space craft, the entire enterprise is the province of the Aerospace Engineer.

Because the energy source is a nuclear fission reactor, we include a Nuclear Engineer, when one becomes available.

(th)

Calliban · 2023-10-02 07:21:58

If you are looking for a way of converting electrical energy into high heat, then radio frequency excitation of a plasma, i.e VASIMR would give the best performance. Plasma is electrically conductive and can therefore be heated using oscillating magnetic fields. You could use a spinning static magnetic field to do the same thing. I don't know why you would do it that way, but it could be done.

Performance would be comparable to other electric propulsion systems. But it has one really big advantage. Given that all plasma is conductive and all materials become plasma at temperatures above 10,000K, really anything you find can be used as propellant. Martian atmospheric CO2, Earth air harvested from the top of the atmosphere, dusty regolith from the moon or an asteroid, ice from a comet. Really anything that you might find can be shoved into this type of engine, heated into plasma and used as propellant. That allows an engine like this to be really versatile, refuelling almost anywhere.

NewMarsMember · 2023-10-02 07:57:57

For Calliban re #3

Thank you for engaging with this topic.

VASIMR is a competitor for this topic!

VASIMR is a linear accelerator. it achieves high ISP but has little thrust.

This topic is about an acceleration method that is NOT linear.

Instead the acceleration method is rotary.

The Spin launch system is a model for this topic.

SpinLaunch is NOT a linear accelerator like VASIMR.

The challenge for a Mechanical Engineer is to improve centrifuge technology to deliver a high volume of accelerated mass at a very high velocity.

The ISP for this topic to reach or exceed is 900.

The mass to be accelerated is defined (for this topic) as 1 kilogram.

The velocity to be achieved for that kilogram is given (for this topic) as 5000 miles per hour, which is demonstrated today by the SpinLaunch system.

An actual centrifuge that exists today can revolve at between 100,000 RPM and 1,000,000 RPM.

|Actual centrifuges available on the market today are NOT designed to release a payload, as is the defining characteristic of the SpinLaunch system.

I am looking for (and encouraging) design of mechanical systems to accelerate a mass (between a gram and a kilogram) to at least 5000 mph and as much faster as the laws of physics and the capabilities of known materials will allow.

As a stretch goal, this topic invites design of a continuous delivery system, as requested by GW Johnson.

Such a system would employ a spiral mechanism to accelerate a mass of molecules to the desired velocity and then direct the molecules through a port in a desired direction.

All systems need to be designed to operate using electric power from a nuclear fission reactor.

The intent of this topic is to find a solution that can be built and demonstrated today, using known technology.

(th)

Last edited by NewMarsMember (2023-10-02 07:58:56)

New Mars Forums

Announcement

#1 2023-10-02 07:00:28

Rotary Motion to Linear Motion - Thermal Activity to Rocket Thrust

#2 2023-10-02 07:12:35

Re: Rotary Motion to Linear Motion - Thermal Activity to Rocket Thrust

#3 2023-10-02 07:21:58

Re: Rotary Motion to Linear Motion - Thermal Activity to Rocket Thrust

#4 2023-10-02 07:57:57

Re: Rotary Motion to Linear Motion - Thermal Activity to Rocket Thrust

Board footer