Project LR1 Skyhammer: A New Shuttle [p1]

[n0mad23]

Are you drafting this with Spacecraft3 then? I've got one of those funny "tickling memory" things going on about a thread from several years ago regarding gimbaling, but haven't been able to find it yet. Obviously such things are outside of Spacecraft3.

Love that screen shot of the craft in orbit. Lovely!

 

[kocmolyf]

Are you drafting this with Spacecraft3 then?

No Spacecraft3 here. I considered it but decided that learning an indirect configuration language rather that just diving into the SDK wasn't a very good use of time. Considering I've already had to add quaternions to the mix to start working out the dynamic moment of inertia, that was probably a good call.

---------- Post added at 08:41 AM ---------- Previous post was at 01:41 AM ----------

Skyhammer on the pad.

Lifting off, just before pitch kick.

In the gravity turn, heads-down.

Droptank jettisoned, heads-up, outer engines shut down.

Just after 400 x 400 km, 60 deg orbital insertion burn.

1. All engine gimbal axes working!
2. Extremely rudimentary staging permits ascent to orbit!
3. Outer engine cutoff at staging point.
4. Aerodynamics are bogus.
5. Still need to implement acceleration limit throttling, orbital insertion is running pretty hot at like 6 gees.
6. Mass properties are still broken. I forgot that I would have to account for more than just cylindrical tank geometry, so have to rethink my approach slightly.
7. And much, much more.

 

[kocmolyf]

Hacked together a basic scenario editor extension which allows you to set the ballasting. I tried a couple of test launches to see what the due east payload from Cape Canaveral was - turns out to be right around 50 tonnes to 400km @28 degrees, almost exactly my first quoted number. 40 tonnes is still the number @60 degrees. I need to redo the editor code, but I proved I can do it.

In addition I made a host of other improvements:

• The main engines can only be ignited on the pad ('Alt + I' ignites and sets full throttle).
• Center engines can throttle down to 60% to reduce the gee load at burnout, outer engines are not throttleable.
• Greatly improved and simplified engine gimbaling. Now roll doesn't couple into pitch and yaw like it used to (this turns out to be a harder problem than it appears).
• Engine gimbals move at a fixed rate (not instantaneous).
• 'Alt + K' shuts down outer engines. Keypad '*' shuts down all engines. Once shut down, engines may not be restarted.
• 'Alt + J' drops the external tanks.

Still to come before the first flight test release:

• Automatic acceleration-limit throttling.
• Spawn an external tank vessel on staging instead of making it vanish.
• Allow resetting the vehicle configuration in the scenario editor.
• Save state integration.
• Real aerodynamics.
• Dynamic center of gravity and moments of inertia.
• Engine startup and shutdown transient thrust.
• Sequential engine shutdown instead of simultaneous to avoid water hammer effects in the feed lines.
• Basic OrbiterSound integration.

 

[MaverickSawyer]

Wow. Coming along swiftly!

 

[kocmolyf]

I had a little bit of free time tonight, so I cleaned up the scenario editor code and added the ability to attach/remove the drop tank.

 

[kocmolyf]

Well, it took me a few hours, but I learned how to set up Orbiter animations. The engines are now animated during gimbal control:

In a hard pitch up + right roll.

I also rolled back the visor and retracted the lower body flap for the launch configuration:

Body flap retracted to protect it from engine plumes during ascent.

Open visor, plus a size comparison with the Shuttle.

Finally, I implemented acceleration-limit throttling and added a couple of simple cues to the HUD for this first WIP release:

1. THR LIM: Engines currently throttled down to maintain acceleration limit.
2. OVER-G: Shut down outer engines immediately.
3. EXT EMPTY: External tank propellant depleted (staging cue).

 

[Nicholander]

Ah, interesting! I just LOVE the idea of this, as the XR2's cargo bay is too small to fit Space Station Building Blocks modules, and the XR5 is absolutely HUGE. I can't wait until it's release! But, I have a few questions:

1. What do you mean by "Modeled in more detail than the XR fleet?" Do you mean the actual model/mesh, or do you mean that in like all the failure/damage simulation, autopilots, and general awesome complexity of the XR fleet? (and the DGIV too!) If it's the latter, then I know that I will LOVE this!

2. Will it be possible to launch the LR1 Skyhammer on a launch vehicle? Like the TX and the HCLV?

3. Will it also be possible to launch this horizontally on a runway? Maybe with some JATO's strapped to the bottom of it during take-off so it can carry the external tank.

 

[kocmolyf]

I had to make some pretty significant changes to the project structure, but I got the drop tank implemented as a separate vessel. The orbiter tops up its tanks from the external feed until empty. Because you can no longer see the drop tank propellant in the glass cockpit, I added a fill indicator that appears at 10% or less.

Droptank vessel visible from the cockpit on the pad.

Throttle about to run out of authority at the end of the 7-engine burn, CUTOFF cue and external fill level percent visible.

Outer engines shut down. External tank is dry, ready to separate.

Drop tank burning up on entry.

 

[Loru]

2. Will it be possible to launch the LR1 Skyhammer on a launch vehicle? Like the TX and the HCLV?

Both TX and HCLV use Payload manager so strapping Skyhammer to them shouldn't be a problem. Real issue is the mass. I don't remember TX' preformance but HCLV can lift 80 tons to LEO in 2 booster config and 120 tons to LEO in 4 booster config, however in latter boosters have significant up/down velocity component at jettison and they may impact the shuttle.

 

[MaverickSawyer]

Both TX and HCLV use Payload manager so strapping Skyhammer to them shouldn't be a problem. Real issue is the mass. I don't remember TX' preformance but HCLV can lift 80 tons to LEO in 2 booster config and 120 tons to LEO in 4 booster config, however in latter boosters have significant up/down velocity component at jettison and they may impact the shuttle.

50 tonnes to LEO sticks to mind for the TX. However, it might be able to give it a serious leg up on your climb to orbit, allowing you to ignore the droptanks entirely.

 

[kocmolyf]

Ah, interesting! I just LOVE the idea of this, as the XR2's cargo bay is too small to fit Space Station Building Blocks modules, and the XR5 is absolutely HUGE.

This is pretty much exactly my motivation. :thumbup:

What do you mean by "Modeled in more detail than the XR fleet?"

I mean in terms of the sophistication of the simulation. I intend to go somewhat beyond the XR fleet in complexity. Obviously that will take time - dbeachy has (presumably) put an enormous amount of time into that code.

Will it be possible to launch the LR1 Skyhammer on a launch vehicle? Like the TX and the HCLV?

You can strap it to them with your add-on of choice, but there is currently no way to ignite the LR1's main engines without ground support equipment (literally, unless you are landed and vertical, the engines will not start). You shouldn't need it though - the LR1 is a realistically-modeled vehicle and is definitely capable of achieving orbit on its own.

I have considered making a variant of the LR1 that uses a flyback booster as the first stage if the expendable tank is your complaint, but that's firmly planted in the future. Expendable lower stages are really a better fit for Orbiter since you can only control one vehicle at a time.

Will it also be possible to launch this horizontally on a runway? Maybe with some JATO's strapped to the bottom of it during take-off so it can carry the external tank.

The LR1 (and its landing gear) are designed to land empty. Fully fueled with the external tank, the LR1 weighs nearly 16 times that much. It just can't take that weight horizontally. Once I complete phase 2 (final approach & landing), the gear will crush in game if you do that.

 

[Nicholander]

Hmm... Well, yes, I already know that it can reach LEO on it's own, but I was just wondering if it was possible.

 

[perseus]

Beautiful addon, I love their research, successor to the Starclipper addon, motivates enthusiasm.
Will have damage model? characteristics of launch and reentry defined ?, which was derived for the central yaw stabilization? , What fuel is used ?, That ISP has theoretically ?, Control Fly-by-wire (FBW) ?,
What is sure is beautiful and simple, yet very complex concept details and characteristics.

 

[kocmolyf]

50 tonnes to LEO sticks to mind for the TX. However, it might be able to give it a serious leg up on your climb to orbit, allowing you to ignore the droptanks entirely.

I was just wondering if it was possible.

The orbiter plus payload is in the 150 tonne range. If you can put about 5300 m/s into it (including gravity losses), and I include an air start kit for the center engines, you should be able to make orbit.

That's an extremely high staging velocity for anything you want to recover, though. It would be tough for anything to survive that, let alone make it back to the launch site.

I will add an air start kit to the scenario editor just for you, though. But it's going to cost you some mass.

Beautiful addon, I love their research, successor to the Starclipper addon, motivates enthusiasm.

Thanks!

Control Fly-by-wire (FBW) ?

Skyhammer is definitely a fly-by-wire spacecraft. As I go through the various stages of development it will begin to pick up an increasingly sophisticated flight computer. I would like to use it to address some problems I have with the available MFDs.

Most of your other questions have been answered in the pages above; I encourage you to read them, or wait and read the first release notes if you prefer.

 

[MaverickSawyer]

The orbiter plus payload is in the 150 tonne range. If you can put about 5300 m/s into it (including gravity losses), and I include an air start kit for the center engines, you should be able to make orbit.

That's an extremely high staging velocity for anything you want to recover, though. It would be tough for anything to survive that, let alone make it back to the launch site.

The TX is a tough bird. It's not uncommon to use her to carry XRs to Mach 4+ and cut them loose to run the ascent on the internal Scramjets. Works better in OMP, but it can be done solo. 5300 m/s might be beyond what you can do with 150 tonnes on her back, though. I think some experiments are in order.

*runs off to refresh Orbiter flying skills*

 

[kocmolyf]

5300 m/s might be beyond what you can do with 150 tonnes on her back, though.

Whoa, sorry. I should have realized that number was fishy. ~150 is the dry mass. When fully fueled (which you'll need to make up the rest of ascent), it tips the scales at more like 520.

 

[NextBigLeap]

Question

How will reentry work? Any AoA and bank control implemented? and will this work with D3D9 client?

 

[kocmolyf]

How will reentry work? Any AoA and bank control implemented? and will this work with D3D9 client?

I think that the stock (delta glider / shuttle) reentry control is pretty insufficient. XR's pitch/bank control is a huge step forward, but still not quite what I'm looking for. I have some plans in this regard but I'm keeping them a secret for now.

Suffice it to say that I care a lot about entry and landing.

 

[MaverickSawyer]

Whoa, sorry. I should have realized that number was fishy. ~150 is the dry mass. When fully fueled (which you'll need to make up the rest of ascent), it tips the scales at more like 520.

*whistles in awe*

 

[kocmolyf]

Finally! :woohoo:

...I don't really have screen captures for this part, although I could have shown lots of entertaining glitches.

I have made both the center of gravity and moments of inertia fully dynamic. This was the hardest thing I've done so far - both because Orbiter really doesn't like center of gravity changes, and because doing computational geometry is hard when you can't draw debugging volumes on screen.

During the process I also discovered / realized a couple of interesting facts:

1. Orbiter completely refuses to adjust a vessel's center of gravity while in ground contact. It will shift all of your meshes, attachment points, etc., but it will snap the CG right back where it was relative to the contact plane.
2. Actually doing center-of-gravity shifting only makes sense when on the ground (ironically). In free flight, moving the center of gravity without using thrust is straight-up warping. In reality, it's the vessel body that moves, not the center of gravity. On the ground, the body can push against the ground to force the CG to move instead. I suspect most of the center-of-gravity shifting in add-ons is actually violating physics for this reason.

As a bonus, I implemented engine thrust transients, so the engine takes a small amount of time to change power level. This has the side effect of making it kind of difficult to time your engine cutoff during orbital insertion, so I'll probably have to make another HUD cue for that.

There are only two large items left before the first release: ascent aerodynamics, and proper (simplified) hinge physics for the drop tank during staging. Then it's a bit of minor cleanup and you guys can take a shot at getting to orbit!