mike wightman
SOC-14 10K
Not even close to the speeds you need though, they max out at around mach 3 ish while you need to hit mach20+. You have to achieve a velocity of at least 7km/s or it just falls back to Earth.
Wanted: Curmudgeony Grognards (to talk TL 5-7 Rockets)
- Thread starter atpollard
- Start date
Spinward Flow
SOC-14 5K
When you do something that the system specifically says you shouldn't do, it's a house rule even if you really feel the system is wrong or incomplete.
Can we agree that this is what LBB2'81 actually says?
You can of course house rule it however you want, but that is still just a house rule.
LBB2 has drive specs governed by formulas.
The difference is that those formulas are obscured/hidden by tables to enforce a mere 10 hull displacements between 100 and 5000 tons (all others need not apply). Why? Because they're unfairly penalized BY GAME DESIGN and presentation format.
The entire point and purpose behind Use next larger size hull for intermediate tonnages that you cite is PURELY there to straight-jacket the design space into an excessively limited (and limiting) finite set of options ... by penalizing all of the other possibilities. It's the mathematical equivalent of saying "there are no fractions" while skipping over integers that ought to be there or allowed. It's excessive pruning purely for the sake of excessive simplicity ... at the expense of a tremendous range of options and possibilities.
Use next larger size hull for intermediate tonnages makes perfect sense if the only hull sizes you CARE ABOUT (as a game designer) or are pre-emptively willing to accept as valid (by unnecessarily penalizing everything else) are limited to:
- 100
- 200
- 400
- 600
- 800
- 1000
- 2000
- 3000
- 4000
- 5000
Or to misquote Hamlet ... "There is more In My Traveller Universe than is dreamt of in your philosophy."
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@Spinward Flow -- I think you're missing the point. It's not that all house rules are bad, it's just that they're not Rules As Written. And that isn't really open to argument; in fact, it's definitional. Something is either printed on the page of a canonical book, or it's not.
Where I find fault is in considering all "house rules" to be equally unsupported by Rules as Written. I understand the concept, but -- especially with LBB2 -- realize that the rules as written can't cover all cases, and were simplified for the expected market. And sometimes, they were implausible enough to break suspension of disbelief (LBB2'77 small craft fuel rules, with their principle -- if not indeed the actual rules -- extended up into starship sizes) and probably should be superseded by house rules.
The best you can manage, I suppose, is to declare up front where you're deviating from RAW and why you think it's justified within the context of the rule set, and leave it to readers to decide whether they think it's a fair deviation.
Where I find fault is in considering all "house rules" to be equally unsupported by Rules as Written. I understand the concept, but -- especially with LBB2 -- realize that the rules as written can't cover all cases, and were simplified for the expected market. And sometimes, they were implausible enough to break suspension of disbelief (LBB2'77 small craft fuel rules, with their principle -- if not indeed the actual rules -- extended up into starship sizes) and probably should be superseded by house rules.
The best you can manage, I suppose, is to declare up front where you're deviating from RAW and why you think it's justified within the context of the rule set, and leave it to readers to decide whether they think it's a fair deviation.
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Anyhow, back to my TL 7 rocket.
I both made progress and suffered a setback. After taking a closer look at both Hard Times and FF&S, I decided to start with a Hard Times design as a point of reference for building a LBB5 Design system for recreating it. Things were going well until I checked the errata and discovered that all the engines had been changed. [sigh]
Ah well, these things always go so much faster the second and third time.
First observation … the weight of a standard hull is BONKERS. Real Rockets are about 4 tonnes per dTon fully loaded. Just the HULL on some of these Ship Design Systems are 5 tonnes per dTonne (and that is before you place anything in it). I may need to borrow a page from FF&S and go with “per G” hull weight/thickness/costs.
From a CT-esque POV: a HULL varies from MCR 0.1 per dT for a custom starship to MCR 0.001 per dTon for an external fuel tank (both of which survive in regular space and Jumpspace). So there is some CT bandwidth in what a “hull” is.
I both made progress and suffered a setback. After taking a closer look at both Hard Times and FF&S, I decided to start with a Hard Times design as a point of reference for building a LBB5 Design system for recreating it. Things were going well until I checked the errata and discovered that all the engines had been changed. [sigh]
Ah well, these things always go so much faster the second and third time.
First observation … the weight of a standard hull is BONKERS. Real Rockets are about 4 tonnes per dTon fully loaded. Just the HULL on some of these Ship Design Systems are 5 tonnes per dTonne (and that is before you place anything in it). I may need to borrow a page from FF&S and go with “per G” hull weight/thickness/costs.
From a CT-esque POV: a HULL varies from MCR 0.1 per dT for a custom starship to MCR 0.001 per dTon for an external fuel tank (both of which survive in regular space and Jumpspace). So there is some CT bandwidth in what a “hull” is.
You're missing [Edit: word choice]
Complexity issues, and there's still the LBB5 [Edit: word choice]
Fair enough, but that's beside the point -- which is that some "house rules" are more justifiable (closer to the intent of RAW) than others. Some are even (though this is probably a bit too far out there) justified enough that many if not most people would accept them in their own settings.
Paraphrasing from my previous post, say what rules you bent or waived, and why you think it's supportable -- then leave it to the audience to decide to use it or not.
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Captain_Ahab
SOC-9
How about designing a space gun with FF&S to launch a scramjet 2nd stage and a payload 3rd?What you want is something like a bigger version of this (that's an Rb 322 surface-to-air prototype missile Sweden made)
The first stage is a powerful solid fuel booster. For the second in our case you have the ramjets as shown, and add the liquid fuel rocket motor that exhausts out the rear of that stage. It should be cheap enough that as an orbital launch vehicle with 200 kg total load, each round costs so little that you can fire thousands if necessary into orbit to build something over time.
Surely Traveller would be fine with a scaled up version of Project HARP or Babylon
AnotherDilbert
SOC-14 1K
@Spinward Flow
You don't define RAW, I don't define RAW, GDW defines RAW.
You can change whatever you want, and it's a house rule. There is nothing wrong with a house rule, it just isn't RAW.
You don't define RAW, I don't define RAW, GDW defines RAW.
You can change whatever you want, and it's a house rule. There is nothing wrong with a house rule, it just isn't RAW.
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AnotherDilbert
SOC-14 1K
Yes, I'm probably missing the point. I just don't see much point in doing another LBB2.5, when we already have LBB2 and LBB5 with decades of support. But that's my problem, and has nothing to do with your game.
I once did a completely mass based ship design system, specifically to make living spaces (≈no mass) cheaper, to get more of the really interesting stuff, people, into space. But when I had made it I realised it just wasn't all that different from the system I had based it on, and didn't give significantly different results. So, I scrapped it and went back to the default system.
Some house rules might be more widely acceptable, but we can't a priori say that one is better or more justifiable than another. Beauty lies in the eye of the beholder.
Yes, I think that's the best we can ask for. There's no need to motivate your house rules, your game is your game.
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AnotherDilbert
SOC-14 1K
My FF&S spreadsheet has some rudimentary support for rockets, should work down to TL-7.
Mass of the hull is still a problem, but fuel is the real killer (here with 0.1 Gturn HRF):
300 tonnes of payload in a total 1000 tonne rocket, but you are not going far on 3 minutes of fuel...
AnotherDilbert
SOC-14 1K
Choosing a more efficient cylinder configuration and reducing the "armour" from 38 mm to 2.5 mm and the hull is no longer a problem:
You get plenty of payload (~480 tonnes out of total ~920 tonnes), but you run out of space for fuel (still 0.1 Gturn = 3 min).
I guess multi-stage is needed...
You get plenty of payload (~480 tonnes out of total ~920 tonnes), but you run out of space for fuel (still 0.1 Gturn = 3 min).
I guess multi-stage is needed...
mike wightman
SOC-14 10K
I don't think a TL5-7 rocket has a hull the equivalent of a foot of hard steel use the mass of a vehicle hull rather than a ship.Anyhow, back to my TL 7 rocket.
I both made progress and suffered a setback. After taking a closer look at both Hard Times and FF&S, I decided to start with a Hard Times design as a point of reference for building a LBB5 Design system for recreating it. Things were going well until I checked the errata and discovered that all the engines had been changed. [sigh]
Ah well, these things always go so much faster the second and third time.
First observation … the weight of a standard hull is BONKERS. Real Rockets are about 4 tonnes per dTon fully loaded. Just the HULL on some of these Ship Design Systems are 5 tonnes per dTonne (and that is before you place anything in it). I may need to borrow a page from FF&S and go with “per G” hull weight/thickness/costs.
From a CT-esque POV: a HULL varies from MCR 0.1 per dT for a custom starship to MCR 0.001 per dTon for an external fuel tank (both of which survive in regular space and Jumpspace). So there is some CT bandwidth in what a “hull” is.
Baroun Tardis
SOC-12
T5 is remarkably free of 3I info or bias.... especially in the "engineering section"
The way I read the real anomolies (reactors before printing press, for example) is the King David's Spaceship situation: The 1525 version of Mulder and Skully get ahold of a tablet with auto-translate and "Space Chilton's: repair your fission reactor" , and team up with DaVinci to go ahead and build one.
Baroun Tardis
SOC-12
Keep in mind the regular hull are supposed to be intact after 40+ years of abuse, and still be intact when the loan is paid off.Anyhow, back to my TL 7 rocket.
I both made progress and suffered a setback. After taking a closer look at both Hard Times and FF&S, I decided to start with a Hard Times design as a point of reference for building a LBB5 Design system for recreating it. Things were going well until I checked the errata and discovered that all the engines had been changed. [sigh]
Ah well, these things always go so much faster the second and third time.
First observation … the weight of a standard hull is BONKERS. Real Rockets are about 4 tonnes per dTon fully loaded. Just the HULL on some of these Ship Design Systems are 5 tonnes per dTonne (and that is before you place anything in it). I may need to borrow a page from FF&S and go with “per G” hull weight/thickness/costs.
From a CT-esque POV: a HULL varies from MCR 0.1 per dT for a custom starship to MCR 0.001 per dTon for an external fuel tank (both of which survive in regular space and Jumpspace). So there is some CT bandwidth in what a “hull” is.
Rockets... I think if they last 40 hours of use people are happy, Heck, for first stage boosters 40 minutes or 40 seconds of operational time people are happy.
mike wightman
SOC-14 10K
Some real world perspective
Saturn V - 3000 tonnes, payload to LEO 140 tonnes, payload to TLI 44 tonnes, cost $1.23 billion
*$9 million
Falcon Heavy - 1420 tonnes, payload to LEO 64 tonnes, payload to TLI 16 tonnes, cost $150 million
*$2.3 million
Falcon 9 - 550 tonnes, payload to LEO 17 tonnes, payload to GTO 6 tonnes, cost $60 million
*$3.5 million
Starship (if it works) - 5000 tonnes, payload to LEO 150 tonnes, cost per flight $1 million (note that this is Elon's estimate for when the thing is mature and flying regularly)
*$7 thousand
SLS - 2600 tonnes, payload to LEO 130 tonnes, payload to TLI 46 tonnes, cost $2 billion
*$ 15 million
Space Shuttle - 2000 tonnes, payload to LEO 28 tonnes, payload to GTO 11 tonnes, cost $1.64 billion
*$58 million
Now you know why the shuttle really bit the dust.
And the question really must be asked - why is NASA not just putting money into developing Starship rather than the SLS? Or use three Falcon Heavy flights to get the lunar transfer stuff into orbit?
*Cost/tonne to LEO
Saturn V - 3000 tonnes, payload to LEO 140 tonnes, payload to TLI 44 tonnes, cost $1.23 billion
*$9 million
Falcon Heavy - 1420 tonnes, payload to LEO 64 tonnes, payload to TLI 16 tonnes, cost $150 million
*$2.3 million
Falcon 9 - 550 tonnes, payload to LEO 17 tonnes, payload to GTO 6 tonnes, cost $60 million
*$3.5 million
Starship (if it works) - 5000 tonnes, payload to LEO 150 tonnes, cost per flight $1 million (note that this is Elon's estimate for when the thing is mature and flying regularly)
*$7 thousand
SLS - 2600 tonnes, payload to LEO 130 tonnes, payload to TLI 46 tonnes, cost $2 billion
*$ 15 million
Space Shuttle - 2000 tonnes, payload to LEO 28 tonnes, payload to GTO 11 tonnes, cost $1.64 billion
*$58 million
Now you know why the shuttle really bit the dust.
And the question really must be asked - why is NASA not just putting money into developing Starship rather than the SLS? Or use three Falcon Heavy flights to get the lunar transfer stuff into orbit?
*Cost/tonne to LEO
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I agree ... the actual rules just seemed a good place to start as a FIRST DATA POINT.
Just as a point of interest for Classic Traveller ...
100 dTons was selected because it is the boundary between Small Craft and Starships. It makes a good point of reference for scaling to small craft a fraction of its size (like 50 dTon) or up to common ACS (like 200 dTon). For the CT Striker design, a 100 dTon cube was assumed with 750 square meters of hull surface with Striker Armor 40 = Starship Armor 0.
Striker: Hull (Armor 0) =
- 42 cm of Soft Steel (TL 5) = per dTon: 25 tonnes; MCr 0.005; 3 cu.m.
- 33.6 cm of Hard Steel (TL 6) = per dTon: 20 tonnes; MCr 0.005; 2.5 cu.m.
- 16.8 cm of Composite Laminate (TL 7-9) = per dTon: 8.8 tonnes; MCr 0.013; 1.3 cu.m.
- 8.4 cm of Crystaliron (TL 10-11) = per dTon: 6.3 tonnes; MCr 0.006; 0.63 cu.m.
- 4.8 cm of Superdense (TL 12-13) = per dTon: 5.4 tonnes; MCr 0.005; 0.36 cu.m.
- 2.4 cm of Bonded Superdense (TL 14-15) = per dTon: 2.7 tonnes; MCr 0.005; 0.18 cu.m.
mike wightman
SOC-14 10K
The whole of T5 is Third Imperium et al based, there is no variant technology not found in the OTU. No hyperdrive, no stutterwarp, no tachyon cannons. Compare this with FF&S which had non-OTU technology and a section about using it and designiong your own tech progression.
So DaVinci with the help of a notebook is going to mine radioactives, build centrifuges to concentrate the required elements, develop the mechanical and electronics necessary to control it? Nope, that passes no suspension of disbelief test - they may as well order it from ACME.
Yes and no ... Skylab was a Saturn upper stage and would probably still be with us and part of the ISS if we had a rocket (STS) ready to boost it before its orbit decayed. In any event, the relentless march of TECHNOLOGY and not HULL FAILURE is what threatens the ISS that we have now (launched in 1998 - Twenty-five years and still going strong).
At this point, I don't even have a TL 7 CT Reaction Drive ship to play with yet.
Once I do and I get to the point of comparing dTons to total tonnes to MCr to payload to Delta-V (or G-Turns) ... then I hope to look at some TRANSFER ORBIT "budgets" and see what can be done with an unstreamlined TUG in LEO.
CIS-LUNAR and LAGRANGE Depots first, I think.
BUT ... Right now I still need a CT Rocket design system with the complexity of LBB2 or LBB5! (My FIRST goal).
['cause I be a CT GROGNARD!]
mike wightman
SOC-14 10K
Ok so how about we start with this:
For a TL6 rocket determine the payload you want lifted to LEO and then divide by 0.05 to gat mass of the rocket and payload.
| rocket system | *payload/rocket mass to LEO | cost per tonne to LEO/$million |
|---|---|---|
| Saturn V | 0.05 | 9 |
| Falcon Heavy | 0.05 | 2.3 |
| Falcon 9 | 0.03 | 3.5 |
| Starship | 0.03 | 0.007 |
| SLS | 0.05 | 15 |
| Space Shuttle | 0.014 | 58 |
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AnotherDilbert
SOC-14 1K
I think FF&S rockets are way too much engine, and probably use too little propellant?
Back of the envelope:
Vulcaine 2.1: https://en.wikipedia.org/wiki/Vulcain_(rocket_engine)
Very roughly
1300 kN thrust for 2 tonne 17 m3 (~1.2 Dt) engine.
Burning 140 tonnes of propellant in 7 min? <== suspect? (EDIT: No, that's about right.)
100 Dt is roughly 1000 tonnes requiring 10000 kN thrust for 1 G.
That is 7.5 engine modules: 6 Dt & 15 tonnes.
Burning 150 tonnes LHyd/LOx per minute
Fuel is one part LOx to two parts LHyd by mass, so density ( 1 * 1.1 + 2 * 0.07 ) / 3 ≈ 0.4
150 tonnes is 150 / 0.4 ≈ 375 m3 ≈ 26 Dt / minute. That's not a lot of minutes...
Very roughly:
"100 Dt" thrust: 6 Dt (15 tonnes)
Propellant: 26 Dt (150 tonnes) per minute.
Something like that?
Back of the envelope:
Vulcaine 2.1: https://en.wikipedia.org/wiki/Vulcain_(rocket_engine)
Very roughly
1300 kN thrust for 2 tonne 17 m3 (~1.2 Dt) engine.
Burning 140 tonnes of propellant in 7 min? <== suspect? (EDIT: No, that's about right.)
100 Dt is roughly 1000 tonnes requiring 10000 kN thrust for 1 G.
That is 7.5 engine modules: 6 Dt & 15 tonnes.
Burning 150 tonnes LHyd/LOx per minute
Fuel is one part LOx to two parts LHyd by mass, so density ( 1 * 1.1 + 2 * 0.07 ) / 3 ≈ 0.4
150 tonnes is 150 / 0.4 ≈ 375 m3 ≈ 26 Dt / minute. That's not a lot of minutes...
Very roughly:
"100 Dt" thrust: 6 Dt (15 tonnes)
Propellant: 26 Dt (150 tonnes) per minute.
Something like that?
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