"Realistic" settings for the XR series?

[Usquanigo]

I'm a sucker for realism in sims (and to an extent, in RPGs too). We could argue about the nature of the term, but versimilitude(sp) is a good word too. lol

I absolutely LOVE the XR series. Some of the coolest looking planes out there, expertly coded, highly detailed, and apart from the static pit in the 2 and lack of one at all in the 5, also the most complete. :speakcool:

But one thing that has always bugged me, is that they seem to be fueled by 'magic'. I have recently begun digging into the cfgs, and I see some of this can be tweaked.

Anyone have any input, advice, opinions on how to config these to be the most "realistic" in a near future/next gen/plausible sort of way? (anything from current tech, to known concepts that just haven't been done due to funding, to likely concepts that haven't really been worked on yet because of their newness - I was amazed by the aerospike concept that I only just recently discovered, even more by the fact that it's been around since the 60s lol)

Mostly it's the fuel/DV they have, that they can go to the moon from KSC without a launcher. That's the sort of thing I'm looking at, but anything else that could punch them up (if there is a way, not that I feel there is a need for it, just tossing it out there ) would be good too.

 

[Tommy]

Kulches Energia add-on can launch an XR1, and perhaps an XR2, into LEO.

But really, the main idea behind having scram jets is because you can get into orbit with less mass (since you aren't carrying oxidizer for the scrams) and have a reasonable amount of fuel left. the fuel/DV (at the default "realistic" settings) are reasonable, its the "unobtainium" used to create an airframe that strong, light, and heat resistant that push the boundry, IMHO.

 

[Usquanigo]

Kulches Energia add-on can launch an XR1, and perhaps an XR2, into LEO.

But really, the main idea behind having scram jets is because you can get into orbit with less mass (since you aren't carrying oxidizer for the scrams) and have a reasonable amount of fuel left. the fuel/DV (at the default "realistic" settings) are reasonable, its the "unobtainium" used to create an airframe that strong, light, and heat resistant that push the boundry, IMHO.

Interesting thoughts.

I guess I look at the size, crew/passenger capacity, AND cargo capacity on top of that, then see all the fuel for the rockets _plus_ the scrams, and the RCS and the APU and the LOX and so on, and it makes me wonder.

Having learned of the AeroSpike, I can buy the thrust, but the Shuttle has to have all those boosters and ***monster*** external tank just to make it up there. So that's why I was looking at the fuel side of things.

 

[Tommy]

The shuttle is huge, with a large cross section (high drag), doesn't use aerodynamic lift for ascent, and designed to carry relatively massive amounts of cargo up. It's the spacegoing version of a delivery truck. It's also 30+ year old tech, and LH + LOX isn't the most mass conservative fuel - ISP is lower than some of the more esoteric stuff so more mass is needed to achieve the samethrust.

 

[mjanicki]

If you want to experiment, one thing you might try, for the XR-1 at least, is setting the config to take on less fuel and using a launcher to reach an altitude where scram jets can be used. Such a thing already exists: [ame="http://www.orbithangar.com/searchid.php?ID=2812"]DeltaGlider XR1 with SRB Booster v1.0[/ame]

That way you can restrict the fuel to your liking and also address your concern that the DGs don't need a launcher. You can alter settings for fuel capacity and fuel burn rate in the XR config files. I recall one of them is called MainFuelISP but don't have a config file in front of me to say exactly what the change should be. With some trial and error you should be able to get a vessel that requires a launcher and careful fuel management to your liking.

Although the addon above is for the XR-1, I've used it to attach stock DGs and DG-IVs by copying and editing the necessary config files so try it out and see if it meets your needs.

-- Mike

 

[yagni01]

There are also many settings in the config file you can set to various levels. Try setting everything to 'expert' level.

 

[Usquanigo]

I have tweaked the ISP, set the requirement for 1 main and 1 scram fuel pack to be carried in the cargo bay, bumped the O2 consumption rate and set the LOX amount to a more realistic level as well as bumped the APU burn rate.

All in all, I like it better. I was still able to get to the ISS from a runway takeoff... but at least I was down to less than 10% main fuel left and had to do an RCS x-feed to make sure I didn't miss the station (got REALLY lucky and found I had closed on it even before getting around to my reference point to check it's alt, I was just there, near co-alt and coming up behind it lol).

I liked at least being almost empty. Of course the ability to gas back up to the max at the ISS was a little off-putting. I may change that part of the config too.

(all XR2, btw, but I know these settings can be transferred to the others)

But really, my question here wasn't how to make it more challenging, that's pretty easy to do, it was really more a question of - what's possible today with current tech levels? Just how far "out there" are the XRs? Like I was saying earlier, I can't help but get the feeling they are "fueled by magic", which is off-putting. And all I can do is look at the shuttle, but there too, Tommy had a good point about it's size, drag, fuel choice, design era, and launch method. But then.... why go back to capsules and continue to launch vert? It seems like some eggheads think that a vert launch, pure thrust based, is the best way to get up there, rather than using aerodynamic lift. (though I always thought it made more sense to use lift, personally, but I'm not a rocket scientist. lol)

The HyperDart is supposed to be based on current tech with a little bit of projection and even that will probably require a piggy-back to get orbital (depending on hw CigDriver ultimately decides). I don't know what choice of fuel he's gone with, but I know he's using aero-spikes and bumping propellant storage PSI to cram more on board in a smaller volume. So if even that needs a boost.....

I guess you can see where I'm going. But(!) on the flip side, I only learned about the aero-spike this past week, and here it's been out since the 60s, so it may VERY well be just that I don't really know what's possible today and they may be more accurate than I realize.

So I was kind of asking both, in a sense - just what is actually possible, and how do/should I config them to match that.

 

[Linguofreak]

The "realistic" setting for main engine ISP, and still more the "stock DG" setting, are, for the thrust levels involved, fairly magical. The main engines put out just under 4 gigawatts, or about 5 million horsepower, between them (you can get power by multiplying thrust by exhaust velocity, which for rockets (not jets!) is proportional to exhaust velocity, which is why Orbiter takes ISP in units of m/s). Even the "expert setting" is stretching things. Still, they aren't too outrageously far out, and we'd probably need performance somewhere on that level to make space travel even worthwhile. It's basically a "We might be able to do something like this in 500 years, or we might not" thing. And the design isn't quite optimized like an actual vehicle with those capabilities would be. Realistically, even with the higher ISP's, it would probably have smaller tanks and more cargo capacity, and be optimized as a surface to LEO or GEO truck that would carry cargo up to interplanetary vehicles with low thrusts and high isp's (on the order of several hundred km/s).

But the stock DG setting is good for semi-realistic exploration of the solar system.

 

[Usquanigo]

The "realistic" setting for main engine ISP, and still more the "stock DG" setting, are, for the thrust levels involved, fairly magical. The main engines put out just under 4 gigawatts, or about 5 million horsepower, between them (you can get power by multiplying thrust by exhaust velocity, which for rockets (not jets!) is proportional to exhaust velocity, which is why Orbiter takes ISP in units of m/s). Even the "expert setting" is stretching things. Still, they aren't too outrageously far out, and we'd probably need performance somewhere on that level to make space travel even worthwhile. It's basically a "We might be able to do something like this in 500 years, or we might not" thing. And the design isn't quite optimized like an actual vehicle with those capabilities would be. Realistically, even with the higher ISP's, it would probably have smaller tanks and more cargo capacity, and be optimized as a surface to LEO or GEO truck that would carry cargo up to interplanetary vehicles with low thrusts and high isp's (on the order of several hundred km/s).

But the stock DG setting is good for semi-realistic exploration of the solar system.

500 YEARS?!?! eesh! lol

That's the "magic" part I was talking about. lol For me, "realistic/plausible, but projected" means like the next 50, to *maybe* 100 years (though more like 50).

I think if the XR2 was ALL fuel and 2 pilots it would be more plausible to me, which is why I set it to require 1 tank of each in the cargo hold to attain 100%. I wanted to go higher, but it meant either never having "100%" show in the main guage, or not having any scram fuel at all. So I settled for 1 and 1 there.

I just did a little size comparison and it seems the DG, save for the wings and maybe part of the engines, could fit INSIDE the Atlantis. lol The Ravenstar isn't too much bigger, but it is still a bit, and looks more aero (even though it has less wing area and carries more passengers and cargo). The Vangaurd looks like it could carry the Atlantis though. lol

So, am I to assume then that there is NO way to make these "realistic" performing craft? Using the XR2 for sub-orbital ferrying of light small loads or people, or using a small boost to go LEO to the ISS or LTV-style craft is the kind of thing I'm looking for - something with the cool-ness, level of detail, and of course, completeness of the XR series, but with near future realism. (and for that we can ignore burea-cratic realities for the most part, more a case of "what's possible" than "what will likely be funded")

With the possibility of other propellants, and scrams which use atmosphere for both oxidizer and free mass ejection (so it doesn't have to be carried on-board), and modern materials science, I was hoping this could be tweaked into something quite possible, perchance even likely. (It would be cool if the main engines were toroidal aero-spikes, but I can just 'pretend' that they are and look past that part of it. lol)

 

[SiberianTiger]

So, am I to assume then that there is NO way to make these "realistic" performing craft? Using the XR2 for sub-orbital ferrying of light small loads or people, or using a small boost to go LEO to the ISS or LTV-style craft is the kind of thing I'm looking for - something with the cool-ness, level of detail, and of course, completeness of the XR series, but with near future realism. (and for that we can ignore burea-cratic realities for the most part, more a case of "what's possible" than "what will likely be funded")

It is possible in the real world, but you'd have to persuade the Greens to looks elsewhere first. The realistic one stage space plane has to have a big size (most of its body used up by propellant tanks), and nuclear scramjets for best performance. Having good unobtainium for the thermal shield won't harm at all, of course. You can review the history of the Delta Clipper, Saenger and HOTOL projects to get the idea of what it takes to deliver such a thing to an orbit and back.

 

[Usquanigo]

Saenger

The Silverbird? The thing proposed in the late 30s/early 40s?

I'll have to look into all those other things too.

The "unobtanium" perhaps might not be quite so... carbon-carbon is supposed to have great thermal properties and is a recent creation. Who knows, maybe they can refine it even more and have triple-carbon. lol


-----Post Added-----

The realistic one stage space plane has to have a big size (most of its body used up by propellant tanks)

I was thinking about something like that - the XR5 seems like it might work - if it was full of fuel and nothing else. lol But then as someone mentioned above, with the shuttle's choice of propellent and static bells, perhaps you could do more with less, and if you could also carry a greater pressure than the shuttle does, that would go a long way as well. (or so I would think lol)

 

[SiberianTiger]

The Silverbird? The thing proposed in the late 30s/early 40s?

No, I mean Saenger II:
http://www.astronautix.com/lvs/saegerii.htm


-----Post Added-----


And just to add to that, here's an illustration of Soviet scramjet MG-19 concept (commonly named "Gurkolyot"):

 

[Usquanigo]

The "realistic" setting for main engine ISP, and still more the "stock DG" setting, are, for the thrust levels involved, fairly magical. The main engines put out just under 4 gigawatts, or about 5 million horsepower, between them (you can get power by multiplying thrust by exhaust velocity, which for rockets (not jets!) is proportional to exhaust velocity, which is why Orbiter takes ISP in units of m/s). Even the "expert setting" is stretching things.

I was just looking through the cheat codes.... seems you can set the main engine ISP by hand, and it's not really checked. What would you say the ISP ought to be for current real-world tech, and for say.... 20 years out?

I'm liking it on "Expert", it's sure a hand-ful for even short trips, but no harm in tweaking more.

 

[dbeachy1]

Yes, the cheatcodes will allow you make the ship perform exactly as you want, and the values you set are not range-checked in any way. If you want to make the ship fly using near-future tech only, you should tweak these config values:

#--------------------------------------------------------------------------
# Empty mass in kg
#--------------------------------------------------------------------------
#EmptyMass=16080

#--------------------------------------------------------------------------
# Main fuel tank capacity in kg
#--------------------------------------------------------------------------
#MainTankCapacity=13396.0

#--------------------------------------------------------------------------
# SCRAM fuel tank capacity in kg
#--------------------------------------------------------------------------
#ScramTankCapacity=3350.0

#--------------------------------------------------------------------------
# RCS fuel tank capacity in kg
#--------------------------------------------------------------------------
#RCSTankCapacity=804.0

#--------------------------------------------------------------------------
# APU fuel tank capacity in kg
#--------------------------------------------------------------------------
#APUTankCapacity=268.0

#--------------------------------------------------------------------------
# Main fuel ISP (specific impulse). This determines how much
# main/hover/rcs fuel is burned each second for a given thrust level.
#
# This value overrides the 'MainFuelISP' setting in the [GENERAL] section.
#
# Note: 40000 equates to 'Stock DG (Moon w/large reserve; this is the original stock DG setting)'
#--------------------------------------------------------------------------
#MainFuelISP=40000.0

#--------------------------------------------------------------------------
# Maximum main engine thrust in newtons, PER ENGINE (x2 for total)
#--------------------------------------------------------------------------
#MaxMainThrust=3.023e5

#--------------------------------------------------------------------------
# Maximum hover engine thrust in newtons, PER ENGINE (x2 for total)
#
# Note: internally the three engines are controlled as two separate
# engines: fore and aft.
#--------------------------------------------------------------------------
#MaxHoverThrust=2.0783e5

#--------------------------------------------------------------------------
# Maximum retro engine thrust in newtons, PER ENGINE (x2 for total)
#--------------------------------------------------------------------------
#MaxRetroThrust=6.424e4

#--------------------------------------------------------------------------
# Maximum RCS Jet thrust in newtons; this affects all 14 jets
#--------------------------------------------------------------------------
#MaxRCSThrust=7.85e3

#--------------------------------------------------------------------------
# SCRAM Fuel Heating Value (FHV). The higher the FHV, the more thrust
# is produced from one kg of propellant. Alter this value if you want to
# adjust the maximum SCRAM engine thrust.
#
# Note: the FHV for Hydrogen is 1.42e8 J/kg (joules per kg).
#--------------------------------------------------------------------------
#ScramFHV=3.5e8

By tweaking those cheatcode values you should be able to make the ship fly exactly like you want. As for what those values should actually be for "near-future" tech, I don't know off the top of my head.

 

[Linguofreak]

I was just looking through the cheat codes.... seems you can set the main engine ISP by hand, and it's not really checked. What would you say the ISP ought to be for current real-world tech, and for say.... 20 years out?

I'm liking it on "Expert", it's sure a hand-ful for even short trips, but no harm in tweaking more.

Current real world tech would be around 5,000 m/s for the ISP. There are some technologies that we could probably build but are completely untested that might give you 8,000 to 10,000 m/s. Also, sometimes you'll see jet engines listed with ISP's of 20,000 to 30,000 m/s, but this is because they use air for propellant, and only carry their fuel with them. Their actual exhaust velocity is much lower. (fuel and propellant are two different things. Fuel is where you get your energy from, propellant is what you push out the back).

Also, ion engines can have very high ISP's, over 100,000, but have thrusts much too low to be useful in any kind of vehicle that has to take off from a planetary surface. The real limiting factor is not ISP but power, which is thrust * exhaust velocity (which is equal to ISP for a rocket, but not for a jet). You can only get so high a power to mass ratio without melting or vaporizing your engine.

The stock-DG settings are fairly close to what we know to be possible (thrusts on a level we can get, and ISP's only 4 to 10 times what we know we can get with that thrust level), but how you keep the engine from melting is a big question. However, compared to what you'll see in even some supposedly "hard" sci-fi (ships that can make the trip from Earth to Mars at constant 1g acceleration), the DG is tremendously realistic.

 

[Eagle]

The biggest difference in ISP limiting for near-tech is if you let it go nuclear.

If you stay conventional you can top out near theoretical maximum for LH/LOX engines at the expense of volume (aka shuttle external tank). Or you can use a denser fuel at a lower ISP. Coming up with some dense slurry that offers decent ISP would be 'realistic' near tech.

For a fission engine for Earth launches I would keep in the lower to mid ISP's that are about twice to three times the ISP of a conventional engine. This is so the engine can develop enough thrust to get you to orbit while keeping the power requirements and reactor size to a minimum.

Fusion engines might be near tech, but potentialy give ungodly ISP and power ratings so I'm not going to speculate.

So pick a delta V capablity and an engine type and try to work out the numbers.