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 Post subject: Re: Hard Space Redux
PostPosted: Fri Sep 14, 2018 1:01 pm 
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Cyborg IM1 wrote:
Constant Accel is my preferred method. It really does simplify things when it comes to game mechanics, and at the end of the day it really shouldn't matter too much to the players. If they are that picky, then they have a lot of other problems with any game systems.

Interplanetary travel using constant acceleration to mid-point then decel all at a constant thrust is actually a pretty simple equation if you squint your eyes:

T = 3*sqrt (D/G)

T in time in days
D is distance in AU
G is thrust in "G's" (assumes 10m/s^2)

So for a 1G thrust it gets really simple

T = 3*Sqrt(D)

It is accurate within about 20% but doesn't worry about differences in orbital velocities and docking maneuvers.

Hmmm... This really makes the fusion torch-ship attractive, potentially with small craft using clean "nuclear lightbulbs" for in-atmospheric flight.

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 Post subject: Re: Hard Space Redux
PostPosted: Fri Sep 14, 2018 2:21 pm 
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Golan2072 wrote:
I'm also researching fission-based engines. I'll probably handwave things a little, and abstract a lot. Zozer's excellent Orbital 2100 has some of the rules I need, though I'll probably want somewhat better (more optimistic?) drives than his NTRs.

Potentially Nuclear Lightbulbs?*

The kind of rockets I am looking for are:
1. Work with a fission power-plant ala MGT1/CE.
2. Relatively high delta-V and acceleration (and I'll probably add some "optimistic handwaving" to performance)
3. Work with hydrogen (or water?) propellant/reaction-mass

If possible - without too much radioactive exhaust.

___
* How often do you have to refuel the "bulb" itself, i.e. the uranium gas core? If this is not too often, this seems like an excellent engine for interface craft, as it lacks radioactive exhaust and there are already launch vehicle designs for this.


Those "nuclear lightbulbs" would cause unholy hell if they crash, though. Imagine the entire starport needing decontamination after a the bulb of a craft cracks open. To say nothing of fallout being potentially carried towards inhabited areas by the wind...

Sounds like an excellent weapon for terrorists, too. Imagine 9/11 if those planes had carried radioactive fuel.

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Space isn't remote at all. It's only an hour's drive away if your car could go straight upwards. Sir Frederick Hoyle
Earth is the cradle of humanity, but one cannot live in a cradle forever. Konstantin Tsiolkovsky
Man has earned the right to hold this planet against all comers, by virtue of occasionally producing someone completely bat**** insane. xkcd #556
Just like people, stars can be very important without being terribly bright. Phil Plait, "Bad Astronomy"


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 Post subject: Re: Hard Space Redux
PostPosted: Fri Sep 14, 2018 8:47 pm 
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Sir Chaos wrote:
Golan2072 wrote:
I'm also researching fission-based engines. I'll probably handwave things a little, and abstract a lot. Zozer's excellent Orbital 2100 has some of the rules I need, though I'll probably want somewhat better (more optimistic?) drives than his NTRs.

Potentially Nuclear Lightbulbs?*

The kind of rockets I am looking for are:
1. Work with a fission power-plant ala MGT1/CE.
2. Relatively high delta-V and acceleration (and I'll probably add some "optimistic handwaving" to performance)
3. Work with hydrogen (or water?) propellant/reaction-mass

If possible - without too much radioactive exhaust.

___
* How often do you have to refuel the "bulb" itself, i.e. the uranium gas core? If this is not too often, this seems like an excellent engine for interface craft, as it lacks radioactive exhaust and there are already launch vehicle designs for this.


Those "nuclear lightbulbs" would cause unholy hell if they crash, though. Imagine the entire starport needing decontamination after a the bulb of a craft cracks open. To say nothing of fallout being potentially carried towards inhabited areas by the wind...

Sounds like an excellent weapon for terrorists, too. Imagine 9/11 if those planes had carried radioactive fuel.

So chemical rockets it is? You can't use fusion in an atmosphere either...

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We are but a tiny candle flickering against the darkness of our times.

Stellagama Publishing - Visit our Blog, Den of the Lizard King


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 Post subject: Re: Hard Space Redux
PostPosted: Fri Sep 14, 2018 9:42 pm 
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There was a chemical rocket table in one of the MGT1 books I worked on - %volume needed to reach orbit based on TL, from 6-9. Let me dig it out. That would be a simple table to add for Interface Craft. That makes all spaceships Unstreamlined! :)

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 Post subject: Re: Hard Space Redux
PostPosted: Fri Sep 14, 2018 10:41 pm 
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Joined: Thu Jul 12, 2012 10:11 pm
Posts: 336
Location: Near Frankfurt, Germany
Golan2072 wrote:
Sir Chaos wrote:
Golan2072 wrote:
I'm also researching fission-based engines. I'll probably handwave things a little, and abstract a lot. Zozer's excellent Orbital 2100 has some of the rules I need, though I'll probably want somewhat better (more optimistic?) drives than his NTRs.

Potentially Nuclear Lightbulbs?*

The kind of rockets I am looking for are:
1. Work with a fission power-plant ala MGT1/CE.
2. Relatively high delta-V and acceleration (and I'll probably add some "optimistic handwaving" to performance)
3. Work with hydrogen (or water?) propellant/reaction-mass

If possible - without too much radioactive exhaust.

___
* How often do you have to refuel the "bulb" itself, i.e. the uranium gas core? If this is not too often, this seems like an excellent engine for interface craft, as it lacks radioactive exhaust and there are already launch vehicle designs for this.


Those "nuclear lightbulbs" would cause unholy hell if they crash, though. Imagine the entire starport needing decontamination after a the bulb of a craft cracks open. To say nothing of fallout being potentially carried towards inhabited areas by the wind...

Sounds like an excellent weapon for terrorists, too. Imagine 9/11 if those planes had carried radioactive fuel.

So chemical rockets it is? You can't use fusion in an atmosphere either...


For habitable worlds? I´d say, yes, chemical rockets are the way to go. Space elevators sound like they´re way beyond your setting.

Your nuclear lightbulbs can still be used extensively in systems without habitable planets, or far out away from such planets - here in the Solar System, there´s no reason you couldn´t use them around the asteroid belt or gas giants, for example.

_________________
Space isn't remote at all. It's only an hour's drive away if your car could go straight upwards. Sir Frederick Hoyle
Earth is the cradle of humanity, but one cannot live in a cradle forever. Konstantin Tsiolkovsky
Man has earned the right to hold this planet against all comers, by virtue of occasionally producing someone completely bat**** insane. xkcd #556
Just like people, stars can be very important without being terribly bright. Phil Plait, "Bad Astronomy"


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 Post subject: Re: Hard Space Redux
PostPosted: Sat Sep 15, 2018 8:01 am 
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So we'll have three reaction engine types in Hard Space:

1) Fusion torches - used by starships and fast interplanetary ships. Can maintain constant acceleration/deceleration at high G (typically 1-G). Highly destructive exhaust. Ships with fusion torches use chemical (or ion? or plasma?) thrusters for fine maneuvering (such as docking) where a fusion torch would be too dangerous. Such ships do not land, at least not in most cases but can "dock" with smaller asteroids. Unobtanium (i.e. physically possible but we don't know how to build them yet) but not handwavium.

2) Closed-cycle gas-core fission rockets ("Nuclear Lightbulbs") - used by slower interplanetary craft and interface craft not intended for atmospheric use. Much safer than fusion torches while providing significantly better performance and endurance than chemical rockets. Such ships can land on airless worlds if they have a standard - rather than distributed - hull. Realistic.

3) Chemical rockets - used almost exclusively for atmospheric craft, as well as for fine maneuvering on ships with fusion (or even fission?) rockets. Inefficient but safe. Can land anywhere if they have a streamlined hull and can fly like an airplane if they have a lifting body. Realistic.

By the way, do fusion rockets necessarily mean shipboard fusion reactors? Or are they "simpler" to make (as this is not very fine-controlled fusion)? I have the potential vision of ships with fission reactors and fusion-torch rockets...

I am also going to research Paul Elliott's Orbital: 2100 rules (which are OGL) regarding reaction drives...

_________________
We are but a tiny candle flickering against the darkness of our times.

Stellagama Publishing - Visit our Blog, Den of the Lizard King


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 Post subject: Re: Hard Space Redux
PostPosted: Mon Sep 17, 2018 8:56 pm 
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Also, how's that for a "Universal Lander" usable both on worlds with atmosphere and worlds without it?

https://contest.techbriefs.com/2015/ent ... fense/6232

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 Post subject: Re: Hard Space Redux
PostPosted: Tue Sep 18, 2018 4:24 pm 
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Golan2072 wrote:
So we'll have three reaction engine types in Hard Space:

1) Fusion torches - used by starships and fast interplanetary ships. Can maintain constant acceleration/deceleration at high G (typically 1-G). Highly destructive exhaust. Ships with fusion torches use chemical (or ion? or plasma?) thrusters for fine maneuvering (such as docking) where a fusion torch would be too dangerous. Such ships do not land, at least not in most cases but can "dock" with smaller asteroids. Unobtanium (i.e. physically possible but we don't know how to build them yet) but not handwavium.

2) Closed-cycle gas-core fission rockets ("Nuclear Lightbulbs") - used by slower interplanetary craft and interface craft not intended for atmospheric use. Much safer than fusion torches while providing significantly better performance and endurance than chemical rockets. Such ships can land on airless worlds if they have a standard - rather than distributed - hull. Realistic.

3) Chemical rockets - used almost exclusively for atmospheric craft, as well as for fine maneuvering on ships with fusion (or even fission?) rockets. Inefficient but safe. Can land anywhere if they have a streamlined hull and can fly like an airplane if they have a lifting body. Realistic.

By the way, do fusion rockets necessarily mean shipboard fusion reactors? Or are they "simpler" to make (as this is not very fine-controlled fusion)? I have the potential vision of ships with fission reactors and fusion-torch rockets...

I am also going to research Paul Elliott's Orbital: 2100 rules (which are OGL) regarding reaction drives...


Your Fusion drive wouldn't be a power plant as such, it would use magnetic fields etc, to compress a stream of hydrogen (tritium?) to make it fuse and create the exhaust velocity you need for acceleration.

HOWEVER, once the plasma is flowing, it will create a magnetic field of its own. That magnetic field can be tapped to generate electricity (just wrap the exhaust tube with conductive wire like copper). It slightly reduces the velocity of your exhaust, but probably not significantly. This type of power plant, which can only work when the plasma drive is operating, is called a Magneto-Hydrodynamic Drive (MHD) and is explained in 2300.

So, I would expect that ships with plasma drives, have an MHD built into them, so that when the torch drive is operating, the fission reactor can be placed in standby - thus extending its life quite a bit. The fission plant is then powered up when the torch drive is shut down. So your Maneuver Drive provides power when it is being used, and your Power Plant produces energy when the M-Drive is idle.

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 Post subject: Re: Hard Space Redux
PostPosted: Tue Sep 18, 2018 7:33 pm 
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Cyborg IM1 wrote:
Golan2072 wrote:
So we'll have three reaction engine types in Hard Space:

1) Fusion torches - used by starships and fast interplanetary ships. Can maintain constant acceleration/deceleration at high G (typically 1-G). Highly destructive exhaust. Ships with fusion torches use chemical (or ion? or plasma?) thrusters for fine maneuvering (such as docking) where a fusion torch would be too dangerous. Such ships do not land, at least not in most cases but can "dock" with smaller asteroids. Unobtanium (i.e. physically possible but we don't know how to build them yet) but not handwavium.

2) Closed-cycle gas-core fission rockets ("Nuclear Lightbulbs") - used by slower interplanetary craft and interface craft not intended for atmospheric use. Much safer than fusion torches while providing significantly better performance and endurance than chemical rockets. Such ships can land on airless worlds if they have a standard - rather than distributed - hull. Realistic.

3) Chemical rockets - used almost exclusively for atmospheric craft, as well as for fine maneuvering on ships with fusion (or even fission?) rockets. Inefficient but safe. Can land anywhere if they have a streamlined hull and can fly like an airplane if they have a lifting body. Realistic.

By the way, do fusion rockets necessarily mean shipboard fusion reactors? Or are they "simpler" to make (as this is not very fine-controlled fusion)? I have the potential vision of ships with fission reactors and fusion-torch rockets...

I am also going to research Paul Elliott's Orbital: 2100 rules (which are OGL) regarding reaction drives...


Your Fusion drive wouldn't be a power plant as such, it would use magnetic fields etc, to compress a stream of hydrogen (tritium?) to make it fuse and create the exhaust velocity you need for acceleration.

HOWEVER, once the plasma is flowing, it will create a magnetic field of its own. That magnetic field can be tapped to generate electricity (just wrap the exhaust tube with conductive wire like copper). It slightly reduces the velocity of your exhaust, but probably not significantly. This type of power plant, which can only work when the plasma drive is operating, is called a Magneto-Hydrodynamic Drive (MHD) and is explained in 2300.

So, I would expect that ships with plasma drives, have an MHD built into them, so that when the torch drive is operating, the fission reactor can be placed in standby - thus extending its life quite a bit. The fission plant is then powered up when the torch drive is shut down. So your Maneuver Drive provides power when it is being used, and your Power Plant produces energy when the M-Drive is idle.

Great ideas! Thank you.

_________________
We are but a tiny candle flickering against the darkness of our times.

Stellagama Publishing - Visit our Blog, Den of the Lizard King


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 Post subject: Re: Hard Space Redux
PostPosted: Wed Sep 19, 2018 1:37 pm 
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Golan2072 wrote:
Also, how's that for a "Universal Lander" usable both on worlds with atmosphere and worlds without it?

https://contest.techbriefs.com/2015/ent ... fense/6232


This is a good idea for a generic (not optimized for efficiency) lander that could work anywhere (that's what the sales brochure says anyway...). Personally, I don't think it would be stable in high winds, but that is just me.

On worlds with thicker atmospheres (ATM4+) an advanced space plane (think Space Shuttle Mark 2+) would be much more efficient (lower operating costs) but cost more. Lifecycle costs would still favor the Space Plane though.

Also, I'm not sure I would give up on the Space Elevator idea so quickly. Arthur Clarke predicted it within the 21st Century, so I think that if the infrastructure, and financial will, exists on a world, it would be viable. As in 2300, it is likely that Mars could get one before Earth since it has a lower gravity, making the construction simpler - it would also be a good trial before attempting it on Earth. Given the age of the Hard Space setting, I don't think any world outside the solar system would have one though.

From a setting point of view, I would expect that all three power bloc WANT to build a Space Elevator, but maybe not all 3 have completed them yet. Northern South America and Central Africa are the most likely locations, but Polynesia could also work. Having one completed and one or two under construction could provide some nice background for industrial espionage etc. :)

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