Steve Jackson Games - Site Navigation
Home General Info Follow Us Search Illuminator Store Forums What's New Other Games Ogre GURPS Munchkin Our Games: Home

Go Back   Steve Jackson Games Forums > Roleplaying > GURPS

Reply
 
Thread Tools Display Modes
Old 09-22-2018, 08:03 AM   #1
Michael Thayne
 
Michael Thayne's Avatar
 
Join Date: May 2010
Default [Spaceships] Proposal for building missiles as spaceships

Here's a rough draft of a proposal for building missiles as spaceships. Feedback welcome.

Missiles are built as spaceships from SM+0 (0.1 tons) to SM+3 (3 tons). In the interest of preventing small missiles from being ridiculously cheap, while maintaining smooth continuity with the cost of SM+4 drones, missile systems cost 2% of the cost of an equivalent SM+6 system at SM+0, 3% at SM+1, 5% at SM+2, and 7% at SM+3. Control "rooms" cost $10k regardless of size (miniaturized electronics are expensive!), and have no control stations.

A control room can be designated a missile guidance unit. If this option is chosen, the missile still functions mostly like a spaceship, but is controlled with Artillery (Guided Missile) of a gunner on the launching ship, modified by Handling (not sAcc!). Missile guidance units do not provide computer networks or sensor arrays, and only provide a minimal comm system to receive orders from the launching ship. The launching ship's array may be used to defeat Defensive ECM. A control room must be designated a missile guidance unit if it would have a computer network rated less than C1, or less than a level 1 common/sensor array, given the size and TL.

Missiles can have most system types, but not weapons. Armor that would provide less than 1 dDR per system is prohibited, except streamlined missiles can always have a single Light Alloy system as a "nose cone". Fission reactors and engines are unavailable. Fusion reactors and engines have minim SM+2 and minimum TL10. Antimatter reactors and engines are unavailable through TL10, have minimum SM+2 at TL11, and can be any size at TL12.

Missile launchers work like hangar bays, but are priced as major batteries, and by default have a number of control stations equal to the number found in a same-size control room. They get the same discount for removed control stations as a control room.

I'll post some worked examples later.
Michael Thayne is offline   Reply With Quote
Old 09-22-2018, 09:10 AM   #2
Michael Thayne
 
Michael Thayne's Avatar
 
Join Date: May 2010
Default Re: [Spaceships] Proposal for building missiles as spaceships

Now some worked examples: first, a very generic chemical missile (can be any SM and TL):

Front Hull
[1-6] Fuel Tanks
[core] Control Room

Central Hull
[1-6] Fuel Tanks

Rear Hull
[1-2] Chemical Rocket Engine
[3-6, core] Fuel Tanks

Performance: 6G acceleration, 5.61 mps delta-V. Costs $28.3K for the SM+0 version, $37.5K for the SM+1 version, $56.2K for the SM+2 version, and $75.7K for the SM+3 version. These costs include the cost of rocket fuel and are rounded to the nearest $100.

These missiles must be remote-guided at TL8. At TL9, a SM+3 drone version becomes available, and minimum drone size decreases by 1 per TL thereafter.
Michael Thayne is offline   Reply With Quote
Old 09-22-2018, 09:49 AM   #3
Michael Thayne
 
Michael Thayne's Avatar
 
Join Date: May 2010
Default Re: [Spaceships] Proposal for building missiles as spaceships

Here's a sophisticated drone missile, likely to be a mainstay anti-capital ship missile at TL10. It's built on a 1-ton (SM+2) unstreamlined hull.

Front Hull
[1-4] Nanocomposite Armor (Hardened; 8 dDR)
[5] Tactical Array (comm/sensor 3)
[6] Defensive ECM
[core] Control Room (C5 Computer, comm/sensor 1)

Central Hull
[1] Nanocomposite Armor (Hardened; 2 dDR)
[2-3] Defensive ECM
[4-6] Fuel Tanks (0.05 tons fuel pellets providing 5 mps delta-V each)

Rear Hull
[1] Nanocomposite Armor (2 dDR)
[2-6] High-Thurst Fusion Pulse Engine (0.1G acceleration each)
[core] Fuel Tank (0.05 tons fuel pellets providing 5 mps delta-V)

Performance is 0.5G, 20 mps delta-V. Cost is $766k
Michael Thayne is offline   Reply With Quote
Old 09-22-2018, 11:43 AM   #4
AlexanderHowl
 
Join Date: Feb 2016
Default Re: [Spaceships] Proposal for building missiles as spaceships

Well, one problem is that it reduces the cost of missiles by a minimum of 50%, which would be balanced by the fact that their performance would be atrocious, lacking the thrust and/or delta-v to be a threat to anything but stationary targets. For example, a TL9 SM+0 missile constructed as a spaceship would have a Complexity 2 computer in its control room, making it less capable than the average TL9 Tiny Computer.
AlexanderHowl is offline   Reply With Quote
Old 09-22-2018, 02:06 PM   #5
Agemegos
 
Agemegos's Avatar
 
Join Date: May 2005
Location: Oz
Default Re: [Spaceships] Proposal for building missiles as spaceships

Are you going to define some warhead systems?
__________________

Decay is inherent in all composite things.
Nod head. Get treat.
Agemegos is offline   Reply With Quote
Old 09-22-2018, 05:39 PM   #6
Fred Brackin
 
Join Date: Aug 2007
Default Re: [Spaceships] Proposal for building missiles as spaceships

Quote:
Originally Posted by Agemegos View Post
Are you going to define some warhead systems?
Are you trying to reduice missile performance by adding uneccessary components? :)

5.6 to 20 miles per second makes the missiles themselves more formidable than any chemical explosive warhead and effective enough that nukes are only useful if contact can not be achieved.
__________________
Fred Brackin
Fred Brackin is offline   Reply With Quote
Old 09-22-2018, 05:49 PM   #7
Michael Thayne
 
Michael Thayne's Avatar
 
Join Date: May 2010
Default Re: [Spaceships] Proposal for building missiles as spaceships

Quote:
Originally Posted by AlexanderHowl View Post
Well, one problem is that it reduces the cost of missiles by a minimum of 50%, which would be balanced by the fact that their performance would be atrocious, lacking the thrust and/or delta-v to be a threat to anything but stationary targets. For example, a TL9 SM+0 missile constructed as a spaceship would have a Complexity 2 computer in its control room, making it less capable than the average TL9 Tiny Computer.
Performance isn't really "atrocious". The chemical rocket missile above has the same acceleration and only slightly worse delta-V when compared to the TL8 missiles in Spaceships 3. Use HEDM rockets and you get similar performance to TL9 missiles. It's not quite the same, but you can totally hit non-stationary targets.

Not being able to do proximity detonation is a bit of an issue issue, but doesn't matter much for large targets. You could fix it with a warhead system, as mentioned by Agememnos, though that would further degrade performance. I've thought about something like, "when ramming, you get a +4 bonus and possibility of multiple hits, but halve damage" for conventional fragmentation warheads. Nuclear warheads would require a bit more thought.

The missile cost problem strikes me as really, really hard. It's hard to see how to justify a 4-ton missile costing $4 million while an SM+4 drone with only slightly worse performance comes in under $1 million. I've tried to do things in a way that allows for a somewhat smooth transition from small, high-cost-per pound missiles to big, lower cost-per-pound ones. But I wonder if this discrepancy between spaceship costs and missile costs is a result of mixing up costs of mature technologies vs. cost of cutting-edge military hardware. For example, in the real world missiles can indeed cost $1 million / ton, but Wikipedia suggests a price tag for an F-15E that's almost that high ($31.1 million for a bird with a MTOW of 36.7 metric tons).
Michael Thayne is offline   Reply With Quote
Old 09-22-2018, 05:50 PM   #8
Michael Thayne
 
Michael Thayne's Avatar
 
Join Date: May 2010
Default Re: [Spaceships] Proposal for building missiles as spaceships

Quote:
Originally Posted by Fred Brackin View Post
Are you trying to reduice missile performance by adding uneccessary components? :)

5.6 to 20 miles per second makes the missiles themselves more formidable than any chemical explosive warhead and effective enough that nukes are only useful if contact can not be achieved.
Fragmentation can also be used to increase hit probability. Not sure the tradeoff is worth it against capital ships, but might make sense for anti-missile missiles? (Or even anti-fighter missiles.) Not 100% on that.
Michael Thayne is offline   Reply With Quote
Old 09-22-2018, 10:16 PM   #9
Michael Thayne
 
Michael Thayne's Avatar
 
Join Date: May 2010
Default Re: [Spaceships] Proposal for building missiles as spaceships

Another sign Spaceships is being really optimistic about costs in a way that isn't carrying over to missiles: Spaceships 2 lists the cost of upmass at TL8 at $300,000 per ton, which is about $300 per kilogram, which we are not close to if you know anything about real-world space launches. But the book has a perfectly legal HLV build that supports this! So one option: much cheaper missiles, all Spaceships costs are understood to be an ideal for a very mature technology, GM is welcome to slap a 10x surcharge on anything deemed less than fully mature, which might be a lot of military hardware.
Michael Thayne is offline   Reply With Quote
Old 09-22-2018, 10:24 PM   #10
Rupert
 
Rupert's Avatar
 
Join Date: Aug 2004
Location: Wellington, NZ
Default Re: [Spaceships] Proposal for building missiles as spaceships

Spaceships itself notes that prices for limited run ships can be 100-1000 times the calculated price. Military spaceships are probably limited run, though not that limited. Missiles, OTOH, probably aren't really 'limited run' items.
__________________
Rupert Boleyn

"A pessimist is an optimist with a sense of history."
Rupert is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Fnords are Off
[IMG] code is Off
HTML code is Off

Forum Jump


All times are GMT -6. The time now is 06:40 PM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2024, vBulletin Solutions, Inc.