Discussion LKS inspired shuttle concept.

[Lmoy]

The cost is amortized with the use and a single design is used twice. Maybe a single, modular vehicle with a interchangeable cargo bay / crew compartment? Again, no offense intended, i'm only discussing... even FOI has in fact two different spaceplanes, Eridanus (multipurpose) and Delphinus (crew only), but in that case they are VERY different beasts (Eridanus is almost ten times Delphinus by mass).

The issue with that is this crew shuttle, if converted for cargo transport, wouldn't be nearly big enough to fit most satellites like Starchaser would be, which would pretty much defeat the point, because then all you can deliver is cargo, which would again be safer and cheaper to deliver via unmanned launch.

 

[Urwumpe]

The issue with that is this crew shuttle, if converted for cargo transport, wouldn't be nearly big enough to fit most satellites like Starchaser would be, which would pretty much defeat the point, because then all you can deliver is cargo, which would again be safer and cheaper to deliver via unmanned launch.

Yes. What makes a payload bay really special and important is its qualification as EVA platform or the ability to install fixed payloads into your spacecraft. Hauling satellites isn't really where it excels.

If you for example want to repair a satellite, having a large bright payload bay with one or two robot arms and EVA tools is really excellent.

 

[K_Jameson]

Surely, separate launches for cargo and crew are the more rational approach. Anyway, in my previous message about a "modular shuttle", I was thinking at the Starchaser as base design, rather than at this smaller version. In any case, even Starchaser can be pretty small for some cargo roles; for example I don't think that a standard ISS module can fit in its cargo bay.

 

[Loru]

Wait... now that I think about it... what happened to your XR-3 project, Loru?
Sorry for the OT

Mesh has been shipped for coding. That's not my departament now

Oh and... I was reading your table in the previous page and I noticed that for LOX/LH2 you used a mixture ratio of 5, instead of the more common and optimal value that is around 6.

Thanks for pointing that out. That saved me few dozen cubic meters in hydrolox stages.

... for instance I don't see these great differences between this concept and the Starchaser's one. No offense intended!

Well, this one is intended as solely a crew transport, whereas Starchaser is intended as satellite retrieval/maintenance and station support. Starchaser could definitely function as a crew transport, but it's more economical to use a smaller and lighter spaceplane for that purpose if you aren't also hauling cargo up (which can be done safer with unmanned delivery systems anyway). So overall, this seems like a really good idea to me.

:hesaid:

Well - Starchaser is 2 + 3 man shuttle with pretty substantial cargo bay that I don't need at this point.

Surely, separate launches for cargo and crew are the more rational approach. Anyway, in my previous message about a "modular shuttle", I was thinking at the Starchaser as base design, rather than at this smaller version. In any case, even Starchaser can be pretty small for some cargo roles; for example I don't think that a standard ISS module can fit in its cargo bay.

It's significantly smaller - here's comparison:

(Cargo bay is 6 x 3.4 meters)

 

[K_Jameson]

It's significantly smaller - here's comparison:

Surely it is, but to me the difference is still not enough. In my ignorance, I see enormous costs to keep in line two different (but not-so-different) and custom-built spaceplanes when, with some compromises and modularity, I can retain only one of it and do two jobs. This is only my thinking, NO offense intended, I repeat!

For comparison, this is the difference between FOI's Eridanus and Delphinus shuttles, that really are poles apart:



I don't meant that our approach was better... Moreover, the Delphinus orbiter wasn't planned during the Eridanus developing, so there wasn't even a real organic approach at the problem!

Anyway... this new small spaceplane has a really cool design, this is sure.

 

[Lmoy]

I was hoping you'd post a comparison image, Loru!
Now in comparison to Delphinus/Eridanus, Eridanus was intended for station-building, wasn't it? Much more in line with STS in terms of function, and thus it is fairly larger than Starchaser. So a comparison between Eridanus and Starchaser isn't entirely valid, since they were intended to fill different roles.

 

[K_Jameson]

I may have misunderstood the Starchaser's purpose, at this point.

Regarding Eridanus, it was conceived as a sort of "scaled down" and "more sustainable" STS especially regarding the cargo bay, that is 1/3 smaller. The Space Shuttle was still fairly bigger than Eridanus.

 

[kocmolyf]

The only big advantage of sidemounting payloads is the high of the stack. The Space Shuttle did not really have any advantage in safety by being a sidemount, quite contrary in its actual implementation. But from the ground operations perspective, sidemount was perfect.

The ground operations were part of the concern - but my understanding is that the main issue was bending loads - the inline configuration required a more robust (heavier) mating structure.

The relevant Dale D. Myers quote (who served as an administrator both at Rockwell and NASA during Shuttle development):
https://youtu.be/iiYhQtGpRhc?t=1h3m11s

 

[K_Jameson]

A comparison between the original inline version of the Quasar/Eridanus stack and the final layout with the orbiter in the sidemount configuration shows immediately the feeling of "frailty" of the inline arrangement, given partially by the fact that the Eridanus wasn't really conceived with in mind such a placement (the primitive idea of Vittorio, Eridanus creator, was about a plain "replica" of the STS) and thus its aft section don't fit well with the Quasar-220 core stage: look how thin is the "neck" between the rocket and the orbiter.

 

[Lmoy]

There's clear benefits to both side-mount and in-line configurations, but based on everything discussed here I personally would go for side-mount, since it should generally reduce operational cost and complexity, with the penalty to safety being greatly reduced if the design adopts the same features utilised by Eridanus (detachable crew cabin with LES, which would probably be used on an in-line configuration anyway, and launch shield for the heat shield).

This is in no way biased by my opinion that side-mount looks way cooler.

 

[Loru]

If instead of firing all engines at once I fire up boosters first and then core after boosters are empty (turing it into classic TSTO) I can save a lot of fuel.

Numbers from silverbird:

 

[Urwumpe]

If instead of firing all engines at once I fire up boosters first and then core after boosters are empty (turing it into classic TSTO) I can save a lot of fuel.

Hardly surprising, since you don't need to take the tank weight with you after staging for the fuel in the core stage before staging.

BUT: The price is, that you have to trust your core stage engine to work after staging. If you look at the rate at which launches are aborted because an engine was showing just a slightly sluggish reaction to commands, not the best idea for a manned mission.

 

[Loru]

Apollo had 3 staging / firing events and it was manned. I think I can manage single hydrolox engine.

 

[Urwumpe]

Apollo had 3 staging / firing events and it was manned. I think I can manage single hydrolox engine.

Apollo was a large gamble anyway, that was always a few mm away from catastrophic failure during its flights.

Funnily, the J-2 engine failed only on the S-II stages and never on the S-IVB, I am not sure if this is really just luck or dark art.

 

[Loru]

Apollo was a large gamble anyway, that was always a few mm away from catastrophic failure during its flights.

Funnily, the J-2 engine failed only on the S-II stages and never on the S-IVB, I am not sure if this is really just luck or dark art.

Hmm - I'd need 2,6 J-2 engines or single SSME class. Can't imagine starting stage combustion engine inflight. Do you know of any stage combustion engine started in-flight?

 

[Urwumpe]

Hmm - I'd need 2,6 J-2 engines or single SSME class. Can't imagine starting stage combustion engine inflight. Do you know of any stage combustion engine started in-flight?

Not really. The NK-43 was supposed to be started inflight, but that never happened.

 

[Loru]

Fuel tanks for that look tempting.

I think I'll just need to invent hydrolox engine capable of inflight start and around 450 ISP.

 

[Urwumpe]

Fuel tanks for that look tempting.

I think I'll just need to invent hydrolox engine capable of inflight start and around 450 ISP.

Well, depends on the thrust that you need. You could of course also use an existing engine, since they are really available in a wide range. After all who cares if they really had ever the chance to prove that they work?

 

[Lmoy]

Is there any benefit to having the orbiter mounted low on the launch vehicle like STS? I know for STS it was logical because the main engines were in the orbiter and you didn't want them melting the ET, but for this vehicle (especially if you decide to implement a LES) wouldn't it be beneficial to have the orbiter placed higher up on the LV? Because then there's less chance of stuff falling onto it and damaging it.

The only thing I can think of is it would be a little harder to mount the orbiter, and the COG might be easier to work with if it's mounted lower, but then I don't know a whole lot about spaceplane operations, so.

 

[K_Jameson]

Apollo was a large gamble anyway, that was always a few mm away from catastrophic failure during its flights.

This is a mith that I read several times; while it is true that the safety standards weren't those of today and the Apollo missions faced countless problems, "a few mm away from catastrophe" is a bit exaggerated statement regarding the Saturn V launches, IMHO.
That said... Soyuz has various staging events and still is the most reliable manned rocket in the world.
If Loru will chose to use real (existing) engines, realism will impose to chose a model that is actually air-startable or that can support this capability. Not trivial for an SSME-class engine.

Funnily, the J-2 engine failed only on the S-II stages and never on the S-IVB, I am not sure if this is really just luck or dark art.

If I recall correctly, the S-IVB engine on Apollo 6 performed poorly during the first burn and completely fails the in-orbit restart, forcing to use the Apollo SPS to raise the orbit.

---------- Post added at 09:51 PM ---------- Previous post was at 09:28 PM ----------

Is there any benefit to having the orbiter mounted low on the launch vehicle like STS? I know for STS it was logical because the main engines were in the orbiter and you didn't want them melting the ET, but for this vehicle (especially if you decide to implement a LES) wouldn't it be beneficial to have the orbiter placed higher up on the LV? Because then there's less chance of stuff falling onto it and damaging it.

The only thing I can think of is it would be a little harder to mount the orbiter, and the COG might be easier to work with if it's mounted lower, but then I don't know a whole lot about spaceplane operations, so.

With Eridanus we chose to place the orbiter higher for a series of safety and cosmetic reasons:

1) the crew compartment is above the tanks, not directly next to it (the nose cone of the rocket is basically empty space), that is safer in case of a major failure.
2) the LES has a wider free horizon in case of use.
3) the crew compartment isn't subject to the falling pieces of foam, eliminating the need of protecting it and thus requiring a somewhat smaller protection shield for the spaceplane during the launch.
4) the spaceplane is better placed during the final run, when the core stage is almost empty and the engines must gimbal even more to match the CoG that migrate laterally. Because our core stage is far smaller and lighter than Energia's one, placing the spaceplane in a Buran-like position would probably require a prohibitive gimbal for the rocket engines to match the CoG in the last seconds of thrust.
5) The stack looked different from STS and Energia-Buran.

Naturally that weird placement of Eridanus, in a real world would pose, I think, significant drawbacks as:
1) Far higher drag especially around the Max-Q
2) Problematic bending loads on the core stage, especially when the stack is on ramp awaiting tankage.