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I have not found a name for a this type of vessel what class a vessel is it? Could it operate similar to a parasail if dropped from a high altitude or orbit with air far thinner then operational design? In a high altitude could it use rocket power with little resistance to achieve orbit while using the thin air for lift?

enter image description here

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  • $\begingroup$ Including more details from the linked question about they type of vehicle you're asking about would help make the question more clear. $\endgroup$ – fooot Dec 25 '16 at 21:52
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    $\begingroup$ This is the only thing I could think of. $\endgroup$ – SMS von der Tann Dec 26 '16 at 1:51
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    $\begingroup$ ....a blimp that doesn't fly? $\endgroup$ – Carlo Felicione Dec 26 '16 at 14:57
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    $\begingroup$ Q: What is a blimp that is not lighter than air? A: A rock. A: A party balloon A: A soccer ball. $\endgroup$ – abelenky Apr 17 '17 at 15:59
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    $\begingroup$ Why do you illustrate your question about a heavier than air with the image of a lighter than air? By the way, could be provide the source of your image? $\endgroup$ – mins Apr 17 '17 at 23:45
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What is a blimp called if it is designed not to be lighter than air?
What is a winged shaped blimp that get its lift from its aerodynamics instead of its buoyancy?

Dynastat

A dynastat is a hybrid airship with fixed wings and/or a lifting body and is typically intended for long-endurance flights. It requires forward flight to create the aerodynamic lift component.

Wikipedia


Blimp

You use the term Blimp, though I suspect you may mean airships in general.

Note that a blimp is "a non-rigid airship without an internal structural framework or a keel.".


Example of Dynastat

Photo of "Airlander" Dynastat in flight
HAV Press Downloads

Hybrid Air Vehicles' Airlander 10 is described as a dynastat and, as I understand it, uses no internal rigid structural members to sustain its shape though it does have fabric membranes and ballonets. It is much closer to a true blimp than to a traditional rigid airship.

Helium filled, laminated fabric construction hull. The hull’s aerodynamic shape, an elliptical cross-section allied to a cambered longitudinal shape, provides up to 40% of the vehicle’s lift. The internal diaphragms required to support this shape allow for a limited amount of compartmentalisation further enhancing the fail-safe nature of the vehicle. Multiple ballonets located fore and aft in each of the hulls provide pressure control

HAV

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  • $\begingroup$ @Muze: By replacing "A Dynastat?" by "A Dynastat is the correct answer." in this answer, don't you think you have gone further than the author intent? You also changed your question, including an image of a dirigible which is not a dynastat, this may now be a bit contradictory.. $\endgroup$ – mins Apr 17 '17 at 23:39
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airship (n.)

a. Originally: any of various aircraft or machines for flying (now rare). Now usually: spec. a dirigible, esp. one having a rigid elongated structure containing gas-filled bags with a compartment for passengers below, which is propeller-driven and steered by means of rudders.

Oxford English Dictionary (online)

Note that the definition does not include "lighter than air" as a requirement. In fact, if this were a requirement then descending blimps and balloons would not qualify as you need to be heavier than air in order to descend without power.

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I think the question you're asking is: what do you call a balloon-based heavier-than-air aircraft which uses aerodynamic lift?

I think the answer is that no such aircraft have ever been built, so there's no name for them. Usually, if your aircraft is heavier than air, there's no point in giving it a balloon.

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    $\begingroup$ Even the old Zeppelins could vary lift by 20% simply by adjusting pitch and speed. Dynamic lift is an essential component when flying dirigibles. $\endgroup$ – Peter Kämpf Dec 26 '16 at 0:26
  • $\begingroup$ 60% of the lift is produced aerostatically by being Lighter-Than-Air and a further 40% lift is generated aerodynamically by having a wing-shaped hull - Hybrid Air Vehicles' Airlander $\endgroup$ – RedGrittyBrick Dec 27 '16 at 22:17
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From the question linked, you're still in the blimp design, so blimp or balloon is correct. A blimp is just a balloon with a steering capability.

Climbing and descending by changing buoyancy

When a balloon needs to climb, it can increase its buoyancy by heating the fluid in its envelop, e.g. heating air. It can also increase the balloon volume by increasing fluid pressure in the envelope. It can also jettison some ballast (e.g. releasing water from ballast tanks).

When a blimp needs to descent, it can decrease its buoyancy, either by replacing fluid by denser fluid (e.g. hot air by cold air) or decreasing envelope volume (by decreasing its internal pressure).

What counts in a blimp/balloon is the average density, as the balloon is subject to two forces: it's weight and its buoyancy. Actually what counts is its density relative to the density of the environment (see below).

enter image description here
A hot air balloon (a Montgolfière) is an open ballon. Source

This is named a "lighter than air". Note that this name is abusive, as the blimp is actually heavier than air when its envelope is not inflated, and when inflated the weight of the fluid adds to its empty weight. It should be named "less dense than air".

Buoyancy has been studied by Archimedes of Syracuse and is explained as: The upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces.

Lighter than carbon dioxide

In your case it's not "lighter than air" as the Martian atmosphere is very thin, and not composed of air --which is mostly nitrogen and oxygen-- but carbon dioxide at very low pressure. Less dense than air wouldn't be enough for some buoyancy to occur.

Blimp / balloon (of Martian kind) is still correct, even when the total buoyancy is negative.

Difference between rocket, balloon and aircraft

All these inventions can climb and move horizontally. They can gain altitude because they have a source of lift. The difference is how this lift is generated:

  • Rocket: Pure reaction from gas exhaust.
  • Balloon: Pure buoyancy.
  • Rotorcraft: Lift created directly by rotating wing.
  • Airplane: This is actually a two-step process: Engine creates horizontal velocity, wing converts horizontal velocity into lift.
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