ShuttleA. How realistic is it? Anything better?

[Clavius0712]

Hi all,

When I first got Orbiter I flew mainly missions in Earth or Luna orbit using ships like the DGIV, XR2 and XR5. These are all great Orbiter ships.

Recently however, I've started flying missions in Jupiter orbit, taking off and landing at PreludeII bases on Callisto, Ganymede and Europa.

Up until now I've been using ships like the XR2 for this but a winged vessel in the Jupiter system isn't very practical from a realism point of view. I have therefore started flying missions using the ShuttleA, one of the stock ships of Orbiter.

My feeling so far, however, is that the ShuttleA isn't very realistic in terms of performance characteristics. It is supposed, for instance, to be capable of achieving orbit in Earth's atmosphere, which I find pretty unlikely. It also lacks the great autopilots of the other ships - in particular the "descent hold" autopilot which I've found to be invaluable for manual vertical landings.

Are there any other ships a bit like the ShuttleA - i.e. designed for flight in a zero or low pressure environment - which are more realistic and have nice autopilots?

 

[the.punk]

Maybe download the total immersion cockpit for shuttle PB on orbithangar.

 

[Eagle]

IIRC the Shuttle A has similar performance to the DG in regards to ISP and delta v.

The unrealistic part is its high thrust and that it has so many strong engines. Also its rather unrealistic to use it for a braking reentry as its superstructure would be exposed to the atmosphere.

So if you accept lightweight, compact, and powerful gas core thrusters then its realistic.

 

[Urwumpe]

It is completely unrealistic, but not without realistic influences - a real spacecraft even with the same technology, would never look like the Shuttle-A.

 

[Ghostrider]

It also lacks the great autopilots of the other ships - in particular the "descent hold" autopilot which I've found to be invaluable for manual vertical landings.

Keep in mind that Shuttle-A belongs to the first batch of Orbiter spacecraft that were included with the standard releases. In-built autopilots began to appear with the DGIII, which is a third-party vehicle. The DeltaGlider series has had a lot of development, while Shuttle-A remained behind (although there was an A2 with damage model). Same with PB, although there has been work there too.

 

[Clavius0712]

Thanks for your replies.

Come on addon developers - why do all our vessels have to be built for Earth flights? Let's have a decent Outer Planets vessel complete with realistic engine thrust, fuel storage and a basic "descent hold" autopilot to make vertical landings easier. The moons of Jupiter and Saturn are vastly underutilized in Orbiter at the moment. I'm bored of flying to the ISS or Brighton Beach from KSC all the time.

Now I'm off to the Orbiter Hanger to see what other ships are there!

 

[Andy44]

If we were to build a realistic Shuttle A, we'd have to make a few changes.

The crew module is good, as is the skeleton frame, so we'll start with those.

We need to get rid of some engines. Let's keep the hoverjets, and nix the main and aux jets. That'll give us some decent thrust, still allow horizontal moon landings, and eliminate needless mass.

Next, give up any notion of atmospheric flight. This thing has no heatshield. If we give it thermal protection, we may be able to aerobrake a bit, but you're not going to land or take off from Earth. This is stricly built for lunar landing and cislunar flight. We will launch it on a booster inside a fairing.

Also, if we want enough delta-V to do Moon-LEO-Moon missions, this thing is going to need a lot bigger propellant tanks and a lot less cargo mass.

I suspect that the propellant tanks may get so large that this thing will become a tail-sitter, similar to Greg Burch's Lunar Ferry.

---------- Post added at 05:25 PM ---------- Previous post was at 05:21 PM ----------

Come on addon developers - why do all our vessels have to be built for Earth flights? Let's have a decent Outer Planets vessel complete with realistic engine thrust, fuel storage and a basic "descent hold" autopilot to make vertical landings easier.

Something like this with a few changes, maybe:

[ame="http://www.orbithangar.com/searchid.php?ID=3174"]Lunar Space Shuttle 0.9[/ame]

It's built for Moon flight, but it can be useful on other light, airless bodies. Perhaps I will build a modified version some day for Outer Planet service...

 

[Hielor]

We need to get rid of some engines. Let's keep the hoverjets, and nix the main and aux jets. That'll give us some decent thrust, still allow horizontal moon landings, and eliminate needless mass.

I'm confused, doesn't getting rid of the main and aux jets basically make the current hovers the mains, just pointed down (which makes flying a pain, since none of the built-in autopilots are designed for that)?

I'd say nix the hovers and mains, and add a second pair of auxes, so you've got both hover and mains available from just one set of engines. Plus, that gets cool points. Maybe not realism points, though...

 

[Andy44]

I'm confused, doesn't getting rid of the main and aux jets basically make the current hovers the mains, just pointed down (which makes flying a pain, since none of the built-in autopilots are designed for that)?

Yes, but in Orbiter the definition of "hover" and "main" is just the difference between a belly-sitter and a tail-sitter.

The Apollo LM, for instance, is a belly-sitter in Orbiter, since the pilot looks to the horizon when landed instead of up at the sky. So what we would call the "main" engine on the real LM is defined as a hoverjet in Orbiter.

ETA: I see what you meant for ease of Orbiter flying...but yeah, gimballed engines are not realistic because the gimbal mechanism is needless mass. The LM didn't use them in real life, and in space you only need to see where you're going when docking or landing. Since we're talking a realistic add-on maybe we need to resolve the whole hover/tailsitter problem with a view change option. I don't code so I don't know how hard that would be.

 

[Hielor]

Yes, but in Orbiter the definition of "hover" and "main" is just the difference between a belly-sitter and a tail-sitter.

The Apollo LM, for instance, is a belly-sitter in Orbiter, since the pilot looks to the horizon when landed instead of up at the sky. So what we would call the "main" engine on the real LM is defined as a hoverjet in Orbiter.

Right, but the LM doesn't need to do complex orbital maneuvering, for which the built-in prograde/retrograde/normal/antinormal autopilots are necessary (assuming that you aren't using something like AttitudeMFD). For hover landings, a "belly sitter" style is more useful, since it's easier to get your bearings. For normal flight, though, a "tail sitter" style (ie: pilot looking along the same axis as the engine's thrust direction) is far more useful and comfortable.

Plus, having the shuttle-A fly around with the pointy end not pointing straight ahead would just look weird

There's another, more practical, reason: with the current model of the Shuttle-A having widely spaced hover engines (as is needed for a stable manually controlled hover craft), if one engine fails you're stuck with extremely limited thrust due to the large torque that would be applied by the remaining one.

 

[yagni01]

I'm confused, doesn't getting rid of the main and aux jets basically make the current hovers the mains, just pointed down (which makes flying a pain, since none of the built-in autopilots are designed for that)?

I'd say nix the hovers and mains, and add a second pair of auxes, so you've got both hover and mains available from just one set of engines. Plus, that gets cool points. Maybe not realism points, though...

That doesn't solve your built-in autopilot problem. . .

 

[Hielor]

ETA: I see what you meant for ease of Orbiter flying...but yeah, gimballed engines are not realistic because the gimbal mechanism is needless mass. The LM didn't use them in real life, and in space you only need to see where you're going when docking or landing. Since we're talking a realistic add-on maybe we need to resolve the whole hover/tailsitter problem with a view change option. I don't code so I don't know how hard that would be.

Well, for a ship that needs to have a wide performance envelope, gimbaling engines could make sense. Plus, the cool factor, man! Don't forget the cool factor!

The view change would be fairly trivial to manage.

---------- Post added at 04:04 PM ---------- Previous post was at 04:03 PM ----------

That doesn't solve your built-in autopilot problem. . .

Well yeah, it does, because the gimballed engines could point to deliver thrust along the +z axis, which is the axis that's pointed in the target direction by the built-in autopilots.

 

[Zatnikitelman]

So perhaps, ditch the mains, and hovers and go strictly gimbaled. In real life that's extra weight and complexity, but if it eases flying, it might be worth it. Then a computer (real life or not) would only have to point the ship one direction instead of having to take into account two frames of reference.

 

[Hielor]

So perhaps, ditch the mains, and hovers and go strictly gimbaled. In real life that's extra weight and complexity, but if it eases flying, it might be worth it. Then a computer (real life or not) would only have to point the ship one direction instead of having to take into account two frames of reference.

Well, it's also not entirely unprecedented in reality. Look at the Harrier.

Presumably at the technology level where you'd need a dedicated small cargo vessel like that which is capable of both landing and small interplanetary journeys, the "extra weight and complexity" may be fairly minimal.

 

[Andy44]

Presumably at the technology level where you'd need a dedicated small cargo vessel like that which is capable of both landing and small interplanetary journeys, the "extra weight and complexity" may be fairly minimal.

Well, maybe, but the thread started with a lament that Shuttle A's Isp is unrealistically high. So if we're using chemical jet propulsion, we're limited by Isp, and there are few possible increases in tech level available for chemical rockets.

But what you ask may be posible if we assume that materials technology will advance to the point where we can lighten the structure of the spacecraft to the point where we can afford a luxury like a gimballed engine. Greg Burch's addons are based on this assumption, and given the advances in nanotech it seems plausible.

A cockpit with a window in the roof (like the Space Shuttle) and a reclining pilot's chair is still simpler...but I agree gimballed engines are cool. Shuttle A2 is very cool, since the aux pod engines are linked to the hover or the main throttles depending on the angle they are at, which makes them very easy to use.

In fact, I always wished someone would combine the best features of Shuttle A (VC, detachable cargo modules, retractable landing gear) with Shuttle A2 (fuel managment system, docking radar, configurable payload options, linked aux pod throttles, damage model with awesome dynamic pressure buffet effect) to make a Super Shuttle A addon.

 

[Eagle]

Well, maybe, but the thread started with a lament that Shuttle A's Isp is unrealistically high. So if we're using chemical jet propulsion, we're limited by Isp, and there are few possible increases in tech level available for chemical rockets.

Chemical? Dang, That reduces you to 3 things low mission delta v, staging, or the big white rocket also known as the flying fuel tank.

At least give yourself an NTR with a Hydrogen medium. 9000m/s gives you an ISP more reasonable to work with for an interplanetary craft.

 

[Hielor]

Well, maybe, but the thread started with a lament that Shuttle A's Isp is unrealistically high. So if we're using chemical jet propulsion, we're limited by Isp, and there are few possible increases in tech level available for chemical rockets.

Well, the problem with that is that in order to get anywhere useful, a chemical engine really needs to have quite a bit more fuel than payload.

 

[Andy44]

Okay, so we can go with an NTR. I think that's what the Ares used in 2001. We're still going to need lots and lots of propellant for a moon-LEO-moon mission profile. Even more if you want to make the transfer windows larger. Just remember not to get too close to it when you're on the ground.

Other realistic propulsion schemes have too little thrust to get off the Moon, so it's either chemical or NTR for the near future, unless we can come up with something better. Maybe if we allow for fusion we can go somewhere.

 

[Clavius0712]

Other realistic propulsion schemes have too little thrust to get off the Moon, so it's either chemical or NTR for the near future, unless we can come up with something better. Maybe if we allow for fusion we can go somewhere.

If it's any help I was setting my scenarios for the Jovian moon trips in 2061. I doubt there would be any sort of colonisation effort around Jupiter earlier than that. Maybe fusion exists by then?

For take off and landing maybe we could use chemical boosters, then switch to some sort of high efficiency/low thrust engine like Ion Drive once orbital?

Great discussion by the way.

 

[Linguofreak]

If it's any help I was setting my scenarios for the Jovian moon trips in 2061. I doubt there would be any sort of colonisation effort around Jupiter earlier than that. Maybe fusion exists by then?

I doubt there would be any colonization effort around Jupiter at all. Which doesn't doom the prospect of a mission to Jupiter, it just says that missions will primarily be exploration and science missions, and that you probably won't see any permanent settlement larger than an ISS-sized research center.

But for best realism, you'd have lander/launchers for the moons, which would dock with an inter-moon shuttle that would never touch the ground. The shuttle would also dock with your Earth-Jupiter ferry. At the Earth end, the ferry would dock with surface-to-orbit winged shuttles.