Project New Lunar Transfer Vessel in the works

[Andy44]

Some of you may be familiar with the Lunar Transfer Vessel:

Well, this being one of my earlier add-ons I've never been completely happy with it. For starters, I meant to have animations from the start but couldn't figure it out, so I got impatient and released it without them. Now that I've figured them out I can do some cool things with this ship.

For starters, I plan to add deployable radiators and comm masts, which must be retracted when the ship is rigged for aerobraking. Other moving parts may be added as well; I want a bigger heatshield but it has to be folded up in segments to fit within the Jupiter III launch vehicle fairing. This will be deployed and locked into place after launch.

Other improvements I plan are a better mesh, especially the truss structure around the payload bay, the foil thermal blankets, the docking ports, and to rework the crew module. I also want to shift the center of mass of the mesh to about the middle of the payload bay, to make the ship easier to handle while docking with cargo aboard (currently the cargo center of mass is forward of the ship's, making linear RCS induce unwanted rotations).

Writing all this down sounds ambitious, but I've done many of these things on my later add-ons, so I think I'm up to the task. Now I just need to find the time...

 

[loading]

Great I always loved your lunar transportation network, and it is great to hear that the LTV gets a facelift.

While looking at is i have a few suggestions / ideas:

- The LTV looks kind of to long to me, mainly for two reasons:
First the mass of the engine and tank is quite far from the heatshield, wich brings some risk of "tipping over" while aerobraking in my opinion.
Second i feel that the safe zone behind the heatshield is ending somewhere aroud the end of the payload bay, so the tank and engine are exposed to the heat.
- There might be some structural load on the heatshield while breaking,
especially when you plan to increase the diameter of the shield.

To solve the problems you could relocate the tank around the crew module (doughnut-shape) and add a few trusses from the end of the payload bay to the outer end of the heatshield.
i would also like some kind of RMS on the Transfer Vehicle to move the cargo modules to the lunar station (not really an issue, URMS can be added to the station)

 

[Andy44]

Yeah, I've thought of the fact that the stern of the ship probably isn't protected very well. I kind of like that toroidal tank idea; I'll have to think about that. It would make it difficult for the crew to see out the windows during formation flying and docking ops, though. On the other hand, I think the current tank is probably too large for its load anyway, though I've never declared exactly what kind of propellant this thing uses. Another benefit of the toroidal tank would be to stiffen the heatshield.

The toroidal tank would also make it a bit more difficult to fit inside the Jupiter III fairing, but I could still segment the edges of the heatshield and stuff it in.

And since passengers occasionally ride in the payload bay, I have to be certain the reactor is far enough away and shielding is adequate for safety.

Certainly worth a look, though, thanks. This is the fun part of development.

As for the RMS, that's something I haven't figured out yet, so I don't know. And in any case, to preserve delta-V, I think the RMS systems belong on the orbital stations rather than the transfer ship. But maybe someday...

 

[ar81]

Sounds very cool!!

 

[Andy44]

Okay, here's a working drawing incorporating some of loading's ideas about shortening the fuselage by moving the tank forward. It's also got three retractable radiator arrays in a possible configuration. The NTR and heatshield are unchanged, just pushed in closer. The payload bay is under reconstruction, too. It has no crew module or comm gear, yet.

Figuring out where to stuff the crew module in here is tough. With the tank up against the heat shield, the dorsal docking port will have to move aft. By moving the whole crew section aft with it, I can make the tank's "donut hole" smaller, which increases tank volume. That hole has to be big enough for a pressurized tunnel to the nose docking port. With the crew module just behind the tank, I can keep some windows in it, too.

The heatshield diameter can be increased without ruining the looks, now, but the edges will have to be folded in to fit inside the launch vehicle. Doing the geometry and mesh cutting for that will be complicated, but doable.

I think I like this new configuration, though, what do you guys think?

---------- Post added at 12:11 AM ---------- Previous post was at 12:06 AM ----------

Something else I just thought of: The toroidal tank in the above pic has a circular cross-section; I could flatten it out a bit, making it elliptical or even a rounded-corner triangle. This would allow the crew module, and everything aft of it, to get a little farther forward, and increase protection for the edges of the tank...have to check that out.

 

[Zatnikitelman]

Looks good Andy! Perhaps what you could do about the heatshield is fold the circle. Like draw a square inside the circle (though not touching the circle). Each circular segment folds inwards so the folded shape is smaller than the fairing size. Um, it's similar to a square circumscribed with a circle, but, it's have to be way offset otherwise the corners would poke out. I'm also curious how the radiators fold in?

 

[Andy44]

The forward edge of each radiator will slide down until the whole thing is a rectangle, like a Japanese fan, and then the rectangle will roll 90 degrees to lay flat against the payload bay truss structure. At least that's the plan.

 

[ijuin]

I really think that there should be some amount of fuel tank blocking the line-of-sight between the crew compartment and the nuclear reactor, since the hydrogen in the fuel would make for an ideal radiation shield and thus keep down on the required shielding mass.

 

[loading]

:speakcool: I kind of like the new configuration, too.

ijuin's idea of using the fuel as a radiation shield sounds good to me.
Maybe a you could use a dome shaped tank and put the CM inside of it.
(this would be easy to model, just add docking tunnel (retractable?) on one side ) Situational awareness while docking operations could also be done with cameras, but to prevent the crew from going mad a little cupola might be nice.

Do the triangular radiators have any advantage apart from looking cool?
In my opinion they are quite unpractical to realise:
Method one scaling to the center : looks like they are made out of elastic material (even possible in reality?)
Method two rotating : looks better, but seems to be complicated in real life (how gets the coolant from one module to the other, integrity of the modules)

I think simple folding rectangular radiators would be more realistic.
(maybe emulating the triangular look by using multiple radiators with increasing length)

Another point: The radiators leave an 120 degree opening around the payload bay, which might be a little small for operations with a RMS.

Are the small radiators around the engine sufficient to cool the NTR on standby, or is it possible to retract only the two lower radiators.

 

[dougkeenan]

OK, slap me silly Andy - why does a lunar vehicle need aerobraking?

 

[Ghostrider]

OK, slap me silly Andy - why does a lunar vehicle need aerobraking?

I suppose someone would also like to come back to Earth orbit with it (or the space around the Moon would soon be crowded with them vehicles) and aerobraking reduces the fuel requirements for getting back into Earth orbit. Probably.

 

[Andy44]

:speakcool: I kind of like the new configuration, too.

ijuin's idea of using the fuel as a radiation shield sounds good to me.
Maybe a you could use a dome shaped tank and put the CM inside of it.
(this would be easy to model, just add docking tunnel (retractable?) on one side ) Situational awareness while docking operations could also be done with cameras, but to prevent the crew from going mad a little cupola might be nice.

The original design of the LTV, pictured in the first post, was built intentionally with the fuel tank between the reactor and the rest of the vehicle. But you asked me to move it...

In any case, the dome-shaped tank might provide shielding for the crew module, but the payload bay, and any passengers riding in it, are out of luck. All shielding must be between the reactor and the payload bay, or the vehicle doesn't meet requirements. There is a small space between the reactor's shield disk and the payload bay; that might be a good place for an auxillary fuel tank or perhaps a water tank. On nuclear submarines, the auxillary diesel fuel tank is placed between the crew quarters and the reactor spaces in a similar manner, and serves the same purpose as a neutron shield.

Do the triangular radiators have any advantage apart from looking cool?
In my opinion they are quite unpractical to realise:
Method one scaling to the center : looks like they are made out of elastic material (even possible in reality?)
Method two rotating : looks better, but seems to be complicated in real life (how gets the coolant from one module to the other, integrity of the modules)

I think simple folding rectangular radiators would be more realistic.
(maybe emulating the triangular look by using multiple radiators with increasing length)

The radiators are actually multiple rectangles fanned out. I don't know if you can actually build them that way, but they look cool, so they stay. Devloper's perogative. This thing has to look cool as well as be semi-realistic, or else what's the fun? I will probably mess witht he textures a bit, though; I'm not sure I like that reddish look.

Another point: The radiators leave an 120 degree opening around the payload bay, which might be a little small for operations with a RMS.

I'll have to think about that. I put the radiators 120 degrees apart so that you can always shunt coolant to whichever ones are in the best shadow, and because it looks cool, like the Tyderion shuttle from Return of the Jedi. But anyway you look at it, having large radiators deployed in any direction makes docking and payload ops a delicate operation.

Are the small radiators around the engine sufficient to cool the NTR on standby, or is it possible to retract only the two lower radiators

I could make the lower radiators separatly retractable, sure. With sc3 it's not a problem. The small radiators are mainly to cool the reactor when the ship is rigged for aerobraking, at which time all external gear must be stowed within the heatshield's envelope.

---------- Post added at 08:40 AM ---------- Previous post was at 08:32 AM ----------

OK, slap me silly Andy - why does a lunar vehicle need aerobraking?

As Ghostrider said, it's so that when returning to LEO from the Moon, you don't need a full 3.2 km/s delta-V to be taken out of your propellant budget's hide.

Aerobraking reduces the necessary delta-V from about 3200 m/s to about a 100 m/s, if you're really good at orbit planning. Generally, it takes a couple of hundred m/s to finish the LEO insertion after the aero phase, along with phasing and rendezvous with the LEO station.

I've gotten very good at aligning planes with the LEO station during the coast phase coming downhill from the moon, which means a lot of propellant savings after the aero phase, since all further maneuvers are in-plane.

It's a fun vehicle to fly, and really gets you to learn the finer points of lunar transfers, especially since my lunar orbit station (LOrbS) is in a polar orbit, making it a challenge to reach it from LEO without lots of messy plane change maneuvers.

 

[Tex]

Very cool Andy, I can't wait!

 

[the.punk]

Yes. I must also say very good work so far.

 

[Andy44]

Okay, a lazy Sunday blown on this. I have built a crew cabin, a better tank with a triangular cross section, finished the keel truss, added comm masts, and put a tank in the little thrust structure area in front of the reactor and behind the payload bay for added radiation protection. The crew cabin may actually be a bit roomier inside than it used to be, and I put some purple-tinted windows on it, including the key one near the dorsal docking tunnel visible in the image.

I also increased the size of both the heat shield and the propellant tank, which makes this thing actually look like it might protect itself from hot plasma.

Unfortunately, this also means it probably won't fit inside the Jupiter III launch vehicle fairing, since the tank is now as big as the heat shield used to be. You can fold a heat shield, maybe, but you can't fold a tank! This means either making a larger fairing (someone needs to do this, anyway) or compromising and making the shield and tank smaller again. Guess which one I'd pick.

Still much work to do: I hate the tank texture, I need to build a recessed nose docking port and a slide-aside heat shield door, and I need to place the RCS thrusters. Maybe paint my company logo or at least a ship name on it somewhere.

I think this thing is gonna be a bit hard on the frame rate, we'll have to see. In any case, I think this is shaping up nicely. I'm really glad you gave me that idea, loading, this ship looks much better like this.

 

[Ark]

Name the config file something other than "LTV", it overrides the files for the ESA LTV lander.

 

[Usquanigo]

Looks sweet. Will it have a pit?

 

[Andy44]

Name the config file something other than "LTV", it overrides the files for the ESA LTV lander.

I don't know what addon you're talking about. I may make all new scenarios for this new one, though, so I'll think about it. And next time, say, "Please" when making demands in my development threads.

Looks sweet. Will it have a pit?

You mean a virtual cockpit? Maybe. I've never done one, before, so that's a new can of worms. But I think this would be a really cool interior, being an odd sort of vessel. The acceleration couches would have to be felxible hammock-like things, so when you are in the aero phase you can lay with your back to the bow, and have your back to the stern during main engine thrust. And you have to be able to see out the upper window when docking.

I may release the vessel first, and then spend some time getting boned up on how to make a VC before updating it. I don't want this to sit around my hard drive forever.

 

[Usquanigo]

You mean a virtual cockpit? Maybe. I've never done one, before, so that's a new can of worms. But I think this would be a really cool interior, being an odd sort of vessel. The acceleration couches would have to be felxible hammock-like things, so when you are in the aero phase you can lay with your back to the bow, and have your back to the stern during main engine thrust. And you have to be able to see out the upper window when docking.

I may release the vessel first, and then spend some time getting boned up on how to make a VC before updating it. I don't want this to sit around my hard drive forever.

That would rock. Panels are "ok", but they tend to look cartoony (which is why I prefer the XR1 over the DG-IV SOOOO much more), and the generic nothing but MFDs can really kill immersion.

I know it's not an easy task, beleive me. I bow to your addon making skills, I can barely make the tutorial rocket, and I still haven't even gotten that thing to fly. But a cockpit would really be the finishing touch especially on something as cool as this.

 

[Andy44]

Well, like I said, don't get your hopes up too high. A VC for me is a whole project in addition to the vessel itself. Something I'd like to do, but it's on the back burner until I finish my current list of stuff.