The Size of a "Dead Glider" ?

[rust]

I am currently working on the logistics of a new setting, and reading the
2300 AD material I re-discovered the concept of the "Dead Glider":

A dead glider is any sort of unpowered reentry vehicle. Dead gliders are quite often disposable, or at least collapsible for ease of transport back to orbit by means of some other interface vehicle. Dead gliders can only be used to get from orbit to surface, and then only on a world with an at-mosphere.
(...)
The streamlined airfoil design of the glider gives it and its payload lift against the atmosphere, allowing it to simply glide to the surface under no power of its own.
(...)
Dead glider landings take approximately three hours from orbit to surface.

This could be an elegant way to deliver supplies to a remote outpost. A
non-streamlined starship enters the system, accelerates for a little while
towards the planet in question, assembles the "dead glider", releases the
"dead glider", and leaves the system again, while the "dead glider" aero-
brakes and lands, preferably not too far from the outpost. And the next
supply ship that is streamlined and actually lands could pick up the parts
of the "dead glider", so it could be reused.

My problem is now that I have no idea what the reasonable size limit for
such a "dead glider" could be. The size of a space shuttle is obviously pos-
sible, but I suspect that there is a maximum size, beyond which the con-
cept does not work well, or not at all.

Any ideas from someone with more knowledge of aerospace engineering
would be most helpful and welcome.

 

[locarno24]

The size of a space shuttle is obviously possible, but I suspect that there is a maximum size, beyond which the concept does not work well, or not at all.

The lift comes from the wing area, and the weight from the volume.

As a result, double all the dimensions and the area goes up by 4 (length x2 and width x2) whilst the volume goes up by 8 (length, width and height x2)

Massive oversimplification, but there you go. Essentially the bigger the glider the bigger its wings have to be in proportion to the glider. I'm sure you could make one of whatever size you like but I wouldn't fancy making one much larger than the current shuttle. Say maxing out at airliner size?

The other reason you wouldn't bother with one much beyond shuttle size is that as you describe it it's a smallcraft. Hence it has to be carried internally in parts or a bay, or in a docking clamp.

The more fundamental limit is going to be the economic one - you're describing a throwaway shuttle.

Fair enough for a pallet/ISO container contraption a dTon or two in size (not unlike the GPS guided parachute rigs you get on C-130s when dropping supplies into war zones) but if I'm dropping something the size of the C-130 I'm going to want it back because even a megafreighter won't be carrying many of them.

 

[rust]

Thank you very much.

Well, again taking the space shuttle as an example, a "dead glider" of
about 90 dtons, which could transport about 75 dtons of supplies with a
mass of up to about 30 metric tons, should be sufficient to supply an
outpost for quite a while with all the stuff its own life support systems
cannot produce.

The "dead glider" could be broken down and the parts could be reused
after a streamlined ship picked them up, or it could be designed so that
most of these parts can be used by the outpost's workshops for manu-
facturing. For example, the body of the "dead glider" could become the
hull of an additional habitat of a growing outpost.

Hmm, seems this concept could make sense in my setting, although less
so in the Third Imperium setting with its higher technology level, which
makes landing and taking off rather easy.

 

[locarno24]

It's a fair enough idea, as you say, for an initial outpost. Essentially, it's an orbital equivalent of 'air-dropping supplies' - something that's worth it if you have multiple start-up colonies in a system; so a trader ship jumps in, makes orbit, looses off a few dozen dead gliders and jumps out again.

Less important on any more developed world - high tech or not, if you've got anything coming back up from the surface (ore or other trade goods) you've got an empty shuttle to go back down, and the ship is probably stopping off to refuel anyway.

 

[rust]

If the thing is disposable, couldn't it be build on a "lifting body" (DynaSoar, X24 etc) or even a dumb old "Sojus" form factor?

I think that any steerable lifting body which would enclose the cargo to
protect it from the heat during the entry into the atmosphere would do.
It should be steerable to ensure that it does not land too far from the
outpost, which could make it difficult to retrieve the supplies, so some-
thing like the spherical Sojuz capsule would probably be a bad idea - as
far as I remember, the Russians usually found it difficult to predict where
exactly it would land.

 

[DFW]

My problem is now that I have no idea what the reasonable size limit for such a "dead glider" could be. The size of a space shuttle is obviously possible, but I suspect that there is a maximum size, beyond which the concept does not work well, or not at all.

Other than material strength limits, there is no real limit to size. Given bonded superdense stuff you could easily have something larger than a C-5.

 

[rust]

Fine, because this is a setting with reaction drives only (no reactionless
drives, no gravitics), and any option to avoid movement out of the gra-
vity well of the planet helps. The more stuff which can be transported to
the planet's surface without having to lift the transport vehicle into orbit
again afterwards, the better. :wink:

 

[GJD]

Dosen't have to be an airfoil shape, you could go with the classic cone shape. If it's dead stick all the way then just calculate the right entry point and let it go ballistic/parachute all the way to the ground - save all the waste space in the wings and probably an autopilot and maneauvering system too. Might be worth looking at some of the reference designs for the proposed Mars cargo landers from Mars direct.

 

[rust]

Might be worth looking at some of the reference designs for the proposed Mars cargo landers from Mars direct.

Thank you for a good idea.

 

[DFW]

Dosen't have to be an airfoil shape, you could go with the classic cone shape. If it's dead stick all the way then just calculate the right entry point and let it go ballistic/parachute all the way to the ground - save all the waste space in the wings and probably an autopilot and maneauvering system too. Might be worth looking at some of the reference designs for the proposed Mars cargo landers from Mars direct.

Excellent. Both the US & Russia used this to bring delicate humans down.

 

[Colin]

In 2300AD, dead gliders and aeroshells are commonly used methods to get cargo and people down from orbit. 2300AD specifically references "collapsible dead gliders" that can be folded down and returned to orbit, possibly via catapult.
Aeroshells are the primary methods for dropping large and/or heavy cargos. With a maneuvering package and a parawing for final descent, they can be aimed quite precisely, generally within a 5 km circle, and military drops are often more precise.
Rust, for your setting I would imagine that a large support vessel could be dropped via aeroshell from orbit, perhaps in a couple of easy to assemble pieces.

 

[DFW]

With a maneuvering package and a parawing for final descent, they can be aimed quite precisely, generally within a 5 km circle, and military drops are often more precise.

We can already hit a runway dead on with autonomous, dead gliders from orbit @TL 7.

 

[rust]

Rust, for your setting I would imagine that a large support vessel could be dropped via aeroshell from orbit, perhaps in a couple of easy to assemble pieces.

Thank you very much for another good idea.

 

[GJD]

Might be worth looking at some of the reference designs for the proposed Mars cargo landers from Mars direct.

Thank you for a good idea.

Of course, they'd need beefing up to survive entry to an Earth type atmosphere.

G.

 

[rust]

Of course, they'd need beefing up to survive entry to an Earth type atmosphere.

Yep, but I think that a hull made of a more advanced material plus a
heat shield should be sufficient for this.

 

[BP]

Why not also carry reaction engine and folded aerodynamic nose/shell casing... if fuel is readily obtainable, then it can be launched back into orbit for quicker reuse.

Especially assuming more advanced engines than today's, reaction fuel might also be feasible to drop with vehicle (or a portion that is less readily manufacture-able).

 

[rust]

Why not also carry reaction engine and folded aerodynamic nose/shell casing... if fuel is readily obtainable, then it can be launched back into orbit for quicker reuse.

Especially assuming more advanced engines than today's, reaction fuel might also be feasible to drop with vehicle (or a portion that is less readily manufacture-able).

This could well become Phase II of the interface transport between orbit
and planetary surface, when the outpost could use the gliders to trans-
port something (e.g. mined crystals, or whatever it has to offer) into or-
bit, but during the Phase I the outpost would most probably have no real
need to do so, since the rare starship actually landing on the planet could
more easily pick up the parts of the disassembled gliders there instead
of "catching" the returned empty gliders in orbit and disassembling them
there.

 

[GJD]

Or, cut doors and Windows into them and use them as colony buildings for those start-up colonies.

 

[rust]

Or, cut doors and Windows into them and use them as colony buildings for those start-up colonies.

Right, or perhaps the materials the gliders are made of can be used for
other purposes. I could imagine that various metal alloys could be both
very useful and impossible to produce at the outpost, so using them to
make the gliders could be a way to deliver them to the outpost.

 

[AndrewW]

Even taking them apart and using them as raw materials could work.