Project Sigma rocket

[Wishbone]

Look for boiloff formulas in the source code of NTR core stage. /me ended up using INSANE number of MLI layers, and did not account for heat leaks through stitches and holes. The formulas can be adapted to LOX (I hope)

 

[N_Molson]

My upper stage is designed as a "big Centaur", so the thermal protection would be equivalent... Since those are designed to be lightweight, that protection is probably limited.

If anyone knows how much time those can stay operational, it would be very interesting data. Also, during the LCROSS mission, the Centaur stage performed a serie of burns over an extended period of time, if I remember well ? Well, I guess that depending of the mission, they might add additional layers of MLI...

 

[K_Jameson]

With the third stage, the stack seems to be a little bit too long... fairly unrealistic to me... however, a very good work on engine modeling and dll development. :thumbup:

 

[n0mad23]

Have you looked into perhaps using cold-fab aerogel for insulation? I'm pretty sure the big industries don't use this type, but in terms of cost it I find the prospect pretty optimistic. If the price could be dropped considerably from the commercially available stuff, I think it's about the best insulation around.

 

[T.Neo]

I would imagine that MLI would be best for in-space insulation, because it is basically using the vacuum of space as the insulation, and minimising heat transfer via electromagnetic radiation (but obviously it is still connected to the rest of the vehicle, so there is heat transfer through the scrim or whatnot).

But: and I am really not sure of this (I would be happily surprised to learn that this isn't the case), but I think MLI cannot withstand being exposed to the aerodynamic forces at launch... which would mean an MLI-enshrouded propellant tank would likely have to be enclosed by the payload fairing.

That in itself is not a bad thing... of course, it's a heavier payload fairing... but the hammerhead could also accomodate larger payloads.

 

[ky]

Will the launcher have its own pad and System Sol, since it is a tad too big for use on the default LC-39.

 

[MaverickSawyer]

...Also, during the LCROSS mission, the Centaur stage performed a serie of burns over an extended period of time, if I remember well ?...

I do know that LCROSS was used for the guidance of the stack, but I don't know if the Centaur was used as anything other than an impactor after LRO seperation...

 

[T.Neo]

I'm pretty sure that Centaur was made inert after it had outlived its usefulness, and for most of the mission, LCROSS was used for all manuvering.

 

[N_Molson]

Will the launcher have its own pad and System Sol, since it is a tad too big for use on the default LC-39.

too big ? It as "only" 1 SSME and 2 SRBs, and is much lighter than the Shuttle stack. And uh, why a special System Sol ?

I'm not planning to model a launchpad right now. I use that one from Orbiter 2010 P2 beta for pics There will be a "launchpad vessel" to manage some effects, but invisible. So people just place it at their favorite spot, adjust the height (easy to add a parameter in the .scn for that), and here they go. I believe it's the most convenient way.

Anyway, yes, that stack is too long. So I cut a good third of the third stage, and now it fits under the fairing used for the HCV version. I have to test how much GTO performance will be degraded (maybe not that much, I think the previous config was not optimal).

But now, the room for payload (especially in the 15 tons range) is obviously insufficient. Maybe extending the fairing by a few meters would be structurally more realistic (since it is supported by the second stage) ?

(Patch by Eli13)

Because a probable loadout for a GTO would be, for 15 tons, 2x 7.5 tons sats or 3x 5 tons sats, so they have to be "piled up".



And I had a hard time to make 3 small Carinas fit ! :lol:

Edit :

The "Centaur-XXL" is now reduced to 40 tons. That's more reasonable. And I can still send 15 tons to GTO with 3700 kg of propellant left (and an unoptimized launch trajectory). With the payload, it makes 55 tons, almost the same that the HCV (53 tons). So the third stage+payload can be orbited by the second stage. Maybe 5-10 more tons of propellant would optimize the "Centaur-XXL", but it implies a minor stretching..

In theory it could enhance the LEO performance, though I think the poor mass/thrust ratio of the "Centaur-XXL" is going to be a limit. Could a thrid RL-10A-4-2 be installed ? Probably, but I think that the heavier versions of the launcher will be best fitted to the task. I'll try, though.

 

[T.Neo]

If the second stage can carry a ~60 ton Megacentaur as well as 15 tons of payload, surely it could accomodate a fairing stretch? I doubt the mass gain would be that significant.

Also, in addition to GTO/BEO performance, could the Megacentaur imrpove LEO performance as well?

 

[N_Molson]

Well, that one offers much more space. The green/blue cylinder is 15 x 4.5 meters big.

But maybe this is fairing madness, what do you think ?





Also, the ACS I set early in the rocket developpement would now be useless, given the shift of CoG (it activates once the SRBs are jettisoned).

 

[T.Neo]

Woah, that's a long payload fairing! :blink:

Maybe mount the payload fairing on the top of stage 3, instead of stage 2, like on the 4-series Atlas? Or perhaps keep the long fairing, but separate after stage 2 shutdown, in microgravity, to maybe reduce stresses or shock forces during fairing separation?

 

[N_Molson]

Yes, attaching the payload to the third stage is probably better. Maybe with some sort of "collar" adapter to make it hold better, like on the AtlasV/Centaur. Maybe some stringers and additional empty mass on the third stage would make the thing more credible, too.

The ultra-long fairing I made would have to be incredibly heavy to stay in one piece, I think. Vibrations, aerodynamic forces, no way.

:idea:I'm thinking to another solution : just make the third and second stage diameters be the same. The LOX tank wouldn't be a sphere then, more like 2 cutted hemispheres, but I don't think this is a problem. The LH2 tank would be a short cylinder with "flat hemispheric" ends. The third stage would be even shorter that way, and the whole thing structurally more "coherent". :hmm:

It would then be easy to add engines and make the stage longer for heavier versions of the rocket.

 

[N_Molson]

"Artist concept" of the Sigma-V launcher. It will be able to haul 200 tons to LEO (Velcro tested).



Characteristics :

Boosters : 4 x 5-segments RSRM
1st stage : 5 x RD-25 (SSME)
2nd stage : 4 x J-2X
Diameter : 10 meters

Here mated with a Dragon capsule for scale comparison.

 

[N_Molson]

Some pics of the third stage that I would name "Centaur XL", as it is basically a big 5 meters diameter Centaur with the same RL10a-4-2 engines.



Detail on the engines plumbing :



And here's a 7 tons communications satellite based on the LS-1300 bus :

 

[N_Molson]

The 3-staged version of the Sigma-I is getting functionnal :

 

[N_Molson]

Painting the 3rd stage, assembled with the rocket :





The fairing and interstage adapter are still untextured (and with the normal maps, it shows !).

 

[N_Molson]

Working on a new, more realistic engine gimbal behavior. So far, the results have been... mitigated, and have put some strain on KSC facilities.



But the Sigma team is working on the problem (hopefully they have a good team of debris cleaners).

---------- Post added at 09:33 PM ---------- Previous post was at 06:24 PM ----------

Got the gimbal system working for the first stage, with engine animation, and I think it's pretty cool, also flight dynamics are much better as some time is required for the engine to gimbal

Next part will be to adapt the autopilot to those new feature... I fear I'll have to make it again from nearly scratch :hmm:

Edit : not that bad, actually. The autopilot tends to "shake" the engine a little wildly, which looks a little weird, but achieve its goals. Some deadzone / dampening settings should make it better.

 

[N_Molson]

OK I've been working on further refinement of the engine gimbal control. It... still doesn't work *perfectly* right now. Well the rocket took off as planned from LC39B and the 10 first seconds of flight were flawless.

On the negative side, my ascent program almost obliterated KSC parking lot. :hide:



US Military official have shown a high interest on the potential destructive power of the LV.

 

[N_Molson]

Sigma-IV Preliminary Design (version B)

Molson Industries, Inc., just released a preliminary design of the future "Sigma-IV" SHLV (Super-Heavy Launch Vehicle). According to this document, the massive rocket would be able to launch up to 220 metric tons of payload in orbit. Applications could strech from 1-piece orbital station deployement to planetary exploration, though nothing has been confirmed yet.

It has also been announced that the "Sigma-I" and "Sigma-V" programs will go through a major redesign.

AstroNews, Tuesday the 7th of May 2013.