 August 20, 2013 - 8:37am | I grew up on a SAC base with KC135s, which was also the plane my Dad happened to do maintenance on so I may just be sentimental about this. That said I was thinking about support ships in another project and it occured to me that the Frontier could have a tanker. Shadow has argued that chem drive ships can certainly reach jump speed with enough fuel bunkerage. naturally a chem drive ship even with enough bunkerage could still find itself in need of a top off of fuel at the other end of the jump, especially if it was forced to do some manuevering. Thus a grapple equipped vessel might be employed in systems where a regular shuttle run by chem drive ships was established. Typically a chem drive ship is expected to carry enough fuel for the accel and decel at both ends of the jump but sometimes a ship has to make course corrections and this could put a chem drive at a deficit for the full trip. I'm thinking that long before atomic drives and or Ion drives became cost effective that the earliest contacts in the frontier were by chem drive ships. such that in the early Frontier and for as long as some shipping lines relied on chem fuel ships that the tanker would have very neccessary use. Later on moth balled tankers could end up being a good buy for a star ship for the PCs I might not be a dralasite, vrusk or yazirian but I do play one in Star Frontiers! |
 August 20, 2013 - 5:07pm | How much does it cost to jump a chem drive ship? How much is the fuel? -iggy |
 August 20, 2013 - 5:58pm | Well, they never really said what the total ADF a single load of chem drive fuel would provide. I've always assumed that it provided 8 ADF worth of thrust. It takes about 2-3 ADF for the space shuttle to get into into orbit and since KH ships seem to land tail first you'd double that giving 4-6 so I just said it was 8. (assuming 1 ADF = 1 g for 10 minutes and ignoring that debate. Actually it doen't affect the final cost answers. ) Since you need 83.33 hours at 1 g to get to jump speed that's 500 ADF of thrust. divide by 8 and thats 62.5 fuel loads. Fuel is listed at 250cr x HS of the ship per engine. So for a HS 5 ship with 3 engines, you get 3750 cr per load. Times 63 loads = 236,250 cr. And that's just to get to jump speed. You need the same to slow down on the other side. So you need a total of 472,500 cr per jump. That same HS 5 ship with Atomic engines only spends 30,000 cr per jump on fuel, a difference of 432,500 cr. The cost of the Chem drives is 300,000 cr. The cost of the Atomic engines cost 1,200,000 credits, a difference of 900,000 cr. So if your chem drive ship is going to have to make more than 2 jumps, it is cheaper to build it with Atomic engines. After three jumps you would have saved 427,500 cr. For a HS 1 ship you get 31,500 cr per jump in chem fuel cost compared to 10,000 cr for atomic engines. In that case you'd need to make 7 jumps for the atomic engines to be more cost effective once you factor in the cost of the engines and the fuel. And that ignores the cost of the tender ship that would have to babysit the chem drive ship and refuel it 62 times and make the jump and refuel it 62 more times before the end. So you can theoretically make jumps in a chem drive ship but you'd be better off just putting ion or atomic engines on it. Ad Astra Per Ardua! My blog - Expanding Frontier Webmaster - The Star Frontiers Network & this site Founding Editor - The Frontier Explorer Magazine Managing Editor - The Star Frontiersman Magazine |
August 20, 2013 - 8:46pm | This is exactly the result I was expecting from the calculations. Chem drive ships are for in system and spend most of the time coasting with the crew living in zero g to preserve fuel. -iggy |
August 21, 2013 - 7:06am | Really, chem drives are for shuttles or really short hauling runs. If you're doing any serious in-system hauling, you build the ship with ion engines. The amount of time you save by being able to be accelerate the whole way there and back is huge and easily makes up for the slightly higher cost of the engines. Example: Earth to Mars, closest approach - The distance between Earth and Mars at opposition is between 55 and 100 million kilometers (it varies due to the eccentricity of their orbits). We'll take an average of 75 million kilometers. Burning 4 ADF and getting up to speed of 40,000 km/10 min and then coasting means that you'll take 312.5 hours or 15.625 days to make the crossing. (Thats in GST days, in earth days its just over 13). That's fast compared to what we can do today. However, if you have a ship that can stay under 1 g for the entire trip, the crossing only takes 78 hours or just under GST days (just over 3 earth days) That's a savings of just under 12 days each trip. Much faster. Costs: Assume a HS 5 ship with 3 engines. The chem fuel as above will cost 3750 cr. And assuming a crew of 2 (Pilot and astrogator) paid at NPC wages for level 1 skills, thats 270 cr/day for 16 days or 4230 cr for a total of 8070 cr per one-way trip. With ion drives, the fuel cost is 10 cr per ADF per engine. You use 6 ADF per hour so the cost is 6 ADF/hour/engine x 78 hours x 3 engines x 10 cr/ADF = 14040 cr. fuel. The crew cost on the other hand is just 4x270 = 1080 cr. for a total of 15120 cr per one way trip. Now that's ~1.9 times more expensive but assuming a 2 day layover at each end for cargo loading, a round trip in the chem drive engine takes 33 days. The round trip in the ion drive engine takes 10 days. So you can make 3 trips in the ion drive engine ship for every single trip in the chem drive engine ship. So you make three times the profit on only double the cost. Even if you only made 40,000 cr gross on the round trip, in that 33 day (call it a month), your net profit would be 5420 cr higher for the ion drive ship. That' pays off the difference between the chem and ion engines in just 28 months or basically 3 years. At 50,000 cr per round trip, the "break even" time is just 6 months. And that's for a short run in the inner system. If you're doing regular hauls out to the outer system, the cost advantage is even higher. Ad Astra Per Ardua! My blog - Expanding Frontier Webmaster - The Star Frontiers Network & this site Founding Editor - The Frontier Explorer Magazine Managing Editor - The Star Frontiersman Magazine |
August 21, 2013 - 8:34am | Clearly the engines dont hold the full ammount of fuel but in the early days of the Frontier before Ion and atomic engines you could build a ship to have a massive fuel tank for the purpose of a void jump. Sure this would have been expensive, dangerous and something only the government would fun but it could be how first contact between humans, dralasites and vrusk occurred. A derelict ship of this design and or a tanker for supporting such ships might make an interesting adventure location. Player might even employ left over fuel in solving of a problem presented in the adventure. I might not be a dralasite, vrusk or yazirian but I do play one in Star Frontiers! |
August 21, 2013 - 3:26pm | Actaully, I don't think you could achieve intersellar speeds with chemical engines. At least not without a refueling system. If you take rockets as efficient as the Space Shuttle main engines (SSMEs), the effective exaust velosity (Ve) is 4423 and to reach 1% c, the mass of the propellent + ship would need to be 3.7 x 10294 times the mass of the ship itself (This is called the mass ratio or MR. Since the mass of all the visible matter in the universe is about 1053 kg. That clearly isn't possible. Heck, even getting 80 minutes at 1 g (8 ADF) out of engines as efficent as the SSMEs reqires an MR of 51656. That is you need 51.6 tons of fuel for every kilogram of ship. Obviously chemical drives in the frontier are way more amazing than real life. If you made the rocket fuel as effiecient as the best ever tested on Earth (Ve = 5342), the fuel is about 20% more effiecient. That 8 ADF worth is still an MR of 7985. And getting to 1% c is still more mass than there is available in the universe (~ 10244) Moving into the realm of modern ion engines, you can get Ve values that are in the range of 25,000 and up. At the low end, say Ve = 30000, the 8 ADF rocket has a MR of just under 5. To get to a full 1%c you're still looking at a huge ratio but now the propellent mass needed to move a 1 kg rocket is less than the mass of the universe. The MR is 2.7 x 1043. Of course if you want to slow down on the other side it's 7.2x1086. At the highest end of modern ion drives we have a Ve of 210,000. That's nearly 47 times more effecient than the SSMEs. This gives us a MR of 1.26 for the 8 ADF ship. Or for every kg of rocket you need 0.26 kg of fuel. For the full jump, to 1%c and back, we're down to 2.6 trillion for the MR. Obviously, the rocket engines in Star Frontiers are truly fantastic to even be able to pull off what they do. Ad Astra Per Ardua! My blog - Expanding Frontier Webmaster - The Star Frontiers Network & this site Founding Editor - The Frontier Explorer Magazine Managing Editor - The Star Frontiersman Magazine |
August 21, 2013 - 5:57pm | TerlObar, I love the analysis. I realy want to work the math backwards from the KH ADF numbers and think up some exotic fuels and engine technology to rationalize it and make SF a little more advanced than us. I'd love to colaberate on an article about the physics of SF space flight and SF engineering technology. Back to Jedion's adventure desires, I think we need to think about how a tanker from current era airplanes could have a parallel in SF. Obviously this is a good use for fighters patrolling in system to top off their fuel and life support. That is an exact parallel to our current era use. Do tankers refuel cargo and passanger planes much for the military? I am having problems making a parallel to this. As far as a tanker refueling a ship trying to jump, my problem is the tanker must reach the speed of the ship trying to jump which would cause it to also use up the fuel it was intending to give to the jumping ship. The next place my mind goes is the the navey oilers and resupply ships. The problem here is that the navy just stops in the ocean to refuel. We are trying to do the refuel at speed. I do however think there could be a parallel to the navey oilers where the ship drops in system and slows down just enough for a rondevous and then the resupply ship matches speed and refuels and aids in the repair and overhaul of engines to save the jump ship the time of getting back to 1%c. Maybe the jump ship slows down to 0.5%c and the oiler matches speed for the repairs, resupply, and overhauls. -iggy |
 August 21, 2013 - 6:16pm | When you absolutely positively need to chem drive yourself there overnight: |
August 21, 2013 - 6:20pm | On a more serious note I have a supply/repair vessel in my game for fleet support, it's essentially a mobile repair/rearming/refueling vessel. The S/R vessel's ADF can be combined with the host ship's ADF for repair work via workpod-like turrets which can also reload and refuel a ship on the fly. As it is laden with supplies, munitions, and fuel it's not a speed demon, so it hangs back while the fleet does the heavy lifting. |
August 21, 2013 - 6:43pm | Well maybe the tanker idea doesn't work, I cant see refueling fighters since they would have an atomic engine to explain their performance and likely as not they just head for the carrier to get turned around. Side note: my Dad was in on the fubar'd Iranian hostage rescue. They tested and perfected a way to refuel helicopters from a KC135 for that mission. Since the KC135 is a jet is flies quite a bit faster than a helicopter. Thus they extended the flap and the landing gear and put it into a stall climb and the helicopter flew like a bat out of hell up behind it and the boom operator would have already deployed the boom so that the helicopter actually perfromed the maneuver to mate with it and get refueled. I got the feeling it that this was a back up plan for refueling helicopters and that all involved were not sweet on it. My Dad seemed rather impressed that they pulled it off and the KC135 didn't fall out of the sky which was a good thing since he was riding in them. This however should be considered an measure of last resort not standard. I might not be a dralasite, vrusk or yazirian but I do play one in Star Frontiers! |
August 21, 2013 - 6:49pm | @iggy, we should definitely do an article. I'm working on one on number of ships in the Frontier as well (the short answer, not as many as you'd think). It's basically an analysis of the starship construction centers. But that's after my sathar destroyer and sathar fleet composition articles. As to oilers and resupply ships and meeting other ships at speed. The problem I see is that you are going to be hard pressed to meet the ship you are trying to support and match velocities with it to effect the resupply and repair if you try to do it at speed. Space is big and you don't know where exactly they are going to come out of the void. It could take you just as long (or longer) to find, catch, and match velocity with them as it would for them to just slow down and meet you somewhere. And you're going to burn a lot of fuel in the process. I have no problem with a tag-along oiler as they'll be moving with you, you just maneuver over and connect. But trying to tag up with a ship already in system is going to be hard/expensive. That opinion of course assumes you're treating spaceflight with real physics, And by that I mainly mean ignoring the completely unrealistic idea of MR which says that a ship with an MR of 3 can pull a 0.02c delta v maneuver in 10 minutes (BTW if anyone is wondering, that's a 10,000 gee maneuver for the full 10 minutes). If that were truly possible, you could get to jump speed in 5 minutes. Velocity is a vector, direction and speed, so if the ship you're supposed to support is coming in at 20 degrees to your current velocity, you've not only got to match their speed but shift your direction by that 20 degrees. And that takes more fuel. And the faster you're going the more it is going to take. And if they are off by several million or tens of millions of miles you got to get extra speed to catch them and then dump it when you get close using up more fuel. It can be done, I just don't know how practical it is. Of course if you allow for MR then all those problems pretty much go away (or are greatly reduced) and it's easy. Ad Astra Per Ardua! My blog - Expanding Frontier Webmaster - The Star Frontiers Network & this site Founding Editor - The Frontier Explorer Magazine Managing Editor - The Star Frontiersman Magazine |
August 21, 2013 - 6:54pm | Side note: my Dad was in on the fubar'd Iranian hostage rescue. They tested and perfected a way to refuel helicopters from a KC135 for that mission. Since the KC135 is a jet is flies quite a bit faster than a helicopter. Thus they extended the flap and the landing gear and put it into a stall climb and the helicopter flew like a bat out of hell up behind it and the boom operator would have already deployed the boom so that the helicopter actually perfromed the maneuver to mate with it and get refueled. I got the feeling it that this was a back up plan for refueling helicopters and that all involved were not sweet on it. My Dad seemed rather impressed that they pulled it off and the KC135 didn't fall out of the sky which was a good thing since he was riding in them. This however should be considered an measure of last resort not standard. Well they obviously figured something else out with other planes that could fly slower because I saw several in air refuelings of helicopters by fixed wing aircraft when I was a kid. From '82-'86 I lived at Ft. Rucker, the army aviation and air assault school where they trained all the helecopter pilots, air traffic controllers, and air assault troops (my day taught air traffic control). One of the strangest things I ever saw was this fixed wing aircarft connected via a boom to a helecopter. That has to be one of the most unnatural sights in the world.  It was so strange the first time I saw it (I'd been living on the base for at least a couple of years) that I had to stop my bike and I stared at it for a good minute or so trying to figure out what I was looking at as it flew across the sky.
Ad Astra Per Ardua! My blog - Expanding Frontier Webmaster - The Star Frontiers Network & this site Founding Editor - The Frontier Explorer Magazine Managing Editor - The Star Frontiersman Magazine |
 August 25, 2013 - 10:38am | Naval vessels are more analogous to spacecraft. Nuclear powered ships still need tenders to replenish weapons and supplies. |
August 25, 2013 - 10:43am | Well they obviously figured something else out with other planes that could fly slower because I saw several in air refuelings of helicopters by fixed wing aircraft when I was a kid. From '82-'86 I lived at Ft. Rucker, the army aviation and air assault school where they trained all the helecopter pilots, air traffic controllers, and air assault troops (my day taught air traffic control). One of the strangest things I ever saw was this fixed wing aircarft connected via a boom to a helecopter. That has to be one of the most unnatural sights in the world.
KC-130s are a turboprop straight wing aircraft commonly used to refuel helicopters. The K-135 is a swept wing jet which makes it a bit more challenging. Do you remember which it was you saw? |
August 25, 2013 - 12:07pm | It was probably the KC-130. I don't think it was a swept wing aircraft. But like I said, this was in the mid 80's so I don't really remember. And the KH rules say that the power comes from the engines. Ad Astra Per Ardua! My blog - Expanding Frontier Webmaster - The Star Frontiers Network & this site Founding Editor - The Frontier Explorer Magazine Managing Editor - The Star Frontiersman Magazine |
August 30, 2013 - 3:51pm | And the KH rules say that the power comes from the engines. Also reaffirmed in Dramune Run where the Gulwind's emergency parabattery that stores 80 hours worth of energy for the basic systems when the drives are off, which are "recharged instantly when the drives are ignited". |
August 31, 2013 - 8:51pm | ??? Recharged Instantly ??? I want to see the super conductors that can handle that? There is a charge time. We should figure one out that fits the future science and the story of the module. Charged Instantly?  The conductors from the engines to the parabattery would become an instant fuse and vaporize. Nice light show and fire for the ship's engineer.-iggy |
August 31, 2013 - 11:10pm | Good find. Are modules considered canon by the purists? I could not find any reference to this subject in the KH Campaign book, original or remastered. It makes perfect sense, but just being nit-picky. |
September 1, 2013 - 4:39am | I would make the BEGIN to recharge instantly. For all intents and purposes if the engines were turned back on they would be used for a longish period of time and you could presume that the next time you needed the battery that it would fully charged. I might not be a dralasite, vrusk or yazirian but I do play one in Star Frontiers! |
