Discussion Orbital Propellant Tanker

MaverickSawyer

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Interesting. I haven't seen many applications of stage-and-a-half other than the Atlas family. Going to be interesting to see how it turns out. Looking nice in all regards, though. Keep up the good work!
 

Hlynkacg

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Just a quick heads up, the red is actually an ablative coating/insulation to help mitigate expansion stresses and prevent corrosion.
 

MaverickSawyer

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Ok, so the white would be from being fired. the dark patches appear to line up with something on the outside of the nozzle bell.
 

T.Neo

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Just a quick heads up, the red is actually an ablative coating/insulation to help mitigate expansion stresses and prevent corrosion.

I always figured that the red coating was the ablative, what I'm wondering is if the RS-68 has (or still has) a red-coloured nozzle interior, rather than a nozzle interior with some other colour.

Ok, so the white would be from being fired. the dark patches appear to line up with something on the outside of the nozzle bell.

What would they line up with though? Shouldn't a fired nozzle be universally charred?

Are flight RS-68s hot-fire tested? I'd imagine that if they are, they would be for this thing as well (and hence the nozzles on OPT could be a charred greyish colour).
 
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MaverickSawyer

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My dad works at Aeojet Sacramento, and deals with the Orion OME. ALL engines flown today are hot fire tested for the entire duration of their intended mission before flight. One of the few instances where a flight engine has not been test fired before flight was the LEM from Apollo.
As for the "charring", I don't think that's charring, but instead changes in the alloy's visual appearance due to the intense heat. If there is something attached to the outside that could absorb more heat, or prevent it from being radiated away, it could change the alloy in a different way than where there is no object on the outside.
 

T.Neo

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Coolant-lines/heat-sink maybe?

Doesn't make sense, since the RS-68 is ablatively cooled. Would that involve heat sinks or coolant lines of any sort?

ALL engines flown today are hot fire tested for the entire duration of their intended mission before flight.

Does that include large, pump-fed booster engines? You did say all, but maybe you're referring to in-space propulsion elements (at least primarily)?

I know SpaceX does acceptance testing on their engines.

As for the "charring", I don't think that's charring, but instead changes in the alloy's visual appearance due to the intense heat. If there is something attached to the outside that could absorb more heat, or prevent it from being radiated away, it could change the alloy in a different way than where there is no object on the outside.

But I thought the inside of the RS-68 nozzle was covered with an ablative, not a metal alloy liner. :idk:

On the other hand, there may be a story behind why this engine looks the way it does. The image description says "Delta IV CBC at the Air Force Space and Missile Museum".

I believe that during development, an entire D-IV CBC was hot fire tested at one of the NASA spaceflight centers (Stennis, I think). Considering that this CBC is being brought to a museum, and looks pretty dirty/weathered, it could be the CBC from that test, which could explain the nozzle charring (but not whether flight nozzles are charred from testing).

Still don't quite 'get' why it would char in that pattern if that's the case though. Does the outside of the nozzle look like it could affect things in that way? I'd imagine the whole point of the ablative being to isolate the nozzle from the exhaust thermally, that the major effects occuring at the surface of the ablative would be dominated by ablation rather than heat being conducted away into the nozzle structure.

Delta4CBC_AFSMM2009RK_05.jpg
 
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MaverickSawyer

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Doesn't make sense, since the RS-68 is ablatively cooled. Would that involve heat sinks or coolant lines of any sort?



Does that include large, pump-fed booster engines? You did say all, but maybe you're referring to in-space propulsion elements (at least primarily)?

I know SpaceX does acceptance testing on their engines.



But I thought the inside of the RS-68 nozzle was covered with an ablative, not a metal alloy liner. :idk:

On the other hand, there may be a story behind why this engine looks the way it does. The image description says "Delta IV CBC at the Air Force Space and Missile Museum".

I believe that during development, an entire D-IV CBC was hot fire tested at one of the NASA spaceflight centers (Stennis, I think). Considering that this CBC is being brought to a museum, and looks pretty dirty/weathered, it could be the CBC from that test, which could explain the nozzle charring (but not whether flight nozzles are charred from testing).

Still don't quite 'get' why it would char in that pattern if that's the case though. Does the outside of the nozzle look like it could affect things in that way? I'd imagine the whole point of the ablative being to isolate the nozzle from the exhaust thermally, that the major effects occuring at the surface of the ablative would be dominated by ablation rather than heat being conducted away into the nozzle structure.

Delta4CBC_AFSMM2009RK_05.jpg

When I say all, i mean ALL liquid fuelled engines, pumps or no pumps. kinda hard to test fire a solid...:lol:
As for cooling, the Merlin-Vac has a radiant-cooling extension. In that case, ANY irregularities can cause tremendous problems. And even ablative nozzles have that problem, although I don't think its nearly as bad.
 

T.Neo

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As for cooling, the Merlin-Vac has a radiant-cooling extension.

Right, but neither the RS-68 nor the first-stage Merlins have use radiative cooling.

In terms of metal being discoloured due to temperature, such an effect is visible on the nozzle of this Vulcain engine:

330px-SNECMA_Vulcain_II.jpg


I'm not using Vulcains though. On the other hand, this would be an absolutely hilarious rocket if I did. :lol:
 

MaverickSawyer

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Point. However, I'm just using that as an example. Also, the ablative is a liner, and is probably just thick enough to make it through the full burn. SOME heat will leak through, and given enough time, it could cause that discoloration. whatever the lines are in this picture, they are spaced in the correct pattern to have been a cause of the darker streaks. although...:hmm:
How long has that CBC been outdoors?
 

T.Neo

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Work on the nosecap fairing continues: this shields the forward avionics, docking port, propellant transfer equipment and any other stuff located in the nose, from aerodynamic and thermal effects during ascent.

attachment.php


The design I went for was a forward-ejecting nosecap with three rocket motors to blast it off the rest of the stack. I'm not sure if this is an optimal arrangement.

I have estimated the mass of those nosecap at around 800 kilograms, and am assuming jettison 340 seconds into the ascent.

The outside is intended to be a sort of composite matrix, the outside white and shiny (I drew inspiration from the the Falcon 9 5m fairing). I still need to add things such as wiring, attachment supports, etc.

The white thing on the inside is the fairing for the avionics cable tunnel- it is still untextured.
 
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T.Neo

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The nosecap has been completed; work is underway on the 'inner' (the bit that sticks with the vehicle) thrust structure. The thing in the image isn't complete, and at some angles anim8or doesn't seem to render things very well.

attachment.php


Since I have very little idea of the actual hardware that would be located in that area, for the most part it is just greebling.

The engines are still the low-poly, horrible-looking stand-ins. Fortunately the 'inner workings' of the final engines should be hidden by a flexible/thermal cloth of some kind, which should save on both modelling effort and framerate performance.
 
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T.Neo

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Early stages of the launch infrastructure:

OPT5.jpg


Red- vehicle.
Blue- launch mount with hold-down posts.
Purple- erector/umbilical tower.
Green- transporter.
Yellow- umbilical tower retracted position.
Light blue- vehicle and launch hardware in transit position (from integration facility to launch site).

The erector hardware as well as the various umbilicals are not yet modelled, but this should give a fairly good impression of the envisioned launch strategy.

It is totally copied from SpaceX. :rofl:
 

T.Neo

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A very interesting entry on Jon Goff's blog. There's some very interesting new technologies being worked on in the US involving MLI, including MLI that can be used in the atmosphere and even on launch vehicles (which is relevant to the earlier discussion in this thread relating to how to effectively insulate a propellant payload-tank from solar radiation on orbit).
 

T.Neo

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THREECOREHEAVY.jpg


The mythical THREE CORE HEAVY!!! variant of OPT. Roughly 200 metric tons to LEO.

Eat your heart out, Mr Musk... your Falcon Heavy is Falcon Lite next to this thing. :lol:

(Ok, admittedly, it is pretty easy when your single-stick vehicle already lifts a payload comparable to FH.)

The four-engine booster 'pack' is permanently bolted to the strapons and the center core has no outer engines at all (just an aerodynamic fairing placed over the aft structure). Fewer engines on the center core means propellant is burnt more slowly and the core acts in effect, like a second stage.

The fairing is 11.5 meters in diameter, and the cylindrical portion is 30 meters long. I intend to have this (or at least a shorter version) as the fairing for cargo-carrying versions of OPT, not just the Heavy.

Accomodating this on the launch pad would probably be a pain, and 'scarring' it into the launch pad for the lighter vehicle might make it ungainly and too large.

Nevertheless, it is more of a "future growth option" that I am taking into account while making the current version. It is pretty much just a distraction. :p

The real work is still 'behind the scenes', and includes a lot of design changes to OPT. The entire boost section has been redone so as to accomodate the actual geometry of the RS-68 engine, and texturing for this part of the vehicle is underway.

I'm really amazed how much the design has changed from the idea as I originally envisioned it. It's a brilliant learning experience.
 

Hlynkacg

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I know I haven't been commenting on this much but I've really enjoyed watching this project come together.

Keep up the good work. :thumbup:
 

T.Neo

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Texturing of the aft body is progressing slowly... it is quite challenging to try and incorperate all the small little details, greebles, items that need to be added to enhance realism. Bolts, seals, access hatches, mounting points for transport and stacking operations, blank-off points for future growth options.

attachment.php


I changed the design of the entire aft body section back in December; the last version had big spaces that vaguely encompassed vague engine shapes. This one does a much better job (I think) of encapsulating the engine geometry, also taking into account gas generator exhausts, etc. The aft body is probably the part of the vehicle that has gone through the most radical changes, and the most iterations.

It is also extremely critical from a realism standpoint: my worry is aerodynamic interactions with the aft end of the vehicle and whether the base heating environment is survivable to the ablative nozzles. Comments/criticism are welcome.
 
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