General Question Venus Landing in XR2?

[Space Dragon]

Hi all is it possible to land on venus and then return to orbit in an XR2?

 

[Nemoricus]

Landing: I see no reason why not. If you're careful about how you reenter, you should be fine. However, this is contingent on the XR2 not crisping to begin with from the temperatures on Venus.

Launching: Unlikely. Depending on how pressure affects the engines, you're not taking off due to Venus's extraordinarily high surface pressure. You just won't get any effective thrust.

You're welcome to try, though.

 

[dbeachy1]

That is correct; the only way to take off from Venus is to "cheat" and set EnableATMThrustReduction=0 in your XR2RavenstarPrefs.cfg file:

#--------------------------------------------------------------------------
# Enable or disable reduction in thrust due to atmospheric pressure.
#   0 = easy (no reduction)
#   1 = realistic (reduction)
#--------------------------------------------------------------------------
EnableATMThrustReduction=0

As for landing, you will be OK as long as you're careful with your hull temps during reentry.

 

[Space Dragon]

ok thanks guys something to think about when I go past that way

 

[Nighthawke]

Hi all is it possible to land on venus and then return to orbit in an XR2?

Well, I guess you could call it landing. If your atmospheric parameters and flight model are set to realistic what actually happens (if you don't skip off of Venus' extremely thick atmosphere) is you slowly sink to Venus' surface. According to the most recent scientific data the atmospheric pressure at Venus' surface is equivalent to the pressure you would encounter at a depth of 1k in the Earth's oceans.

Takeoff is something else entirely. If your parameters are set realistic, may as well forget it. It isn't happening. You can however creep along the ground for quite awhile.

 

[Linguofreak]

As for landing, you will be OK as long as you're careful with your hull temps during reentry.

Well, are the XR2's temp limits different from the XR1's?

If not, then a safe landing is impossible, although you can get as close to the ground as you wish:

I once flew an atmospheric entry on Venus in an XR1, and managed to get down to the surface without busting the temp limits. Then, just above the surface, at low speed and with my hull temperature being the same as the ambient air, I deployed my gear...

With the ship buttoned up for reentry, the surface temps weren't a problem. But the temp limits with gear deployed are lower than the reentry configuration limits. So trying to land turned out to be a rather bad idea.

 

[tylor2000]

Do we have a propeller you might see on a deep sea diving vessel? No thrust except churning water or atmosphere? Just to get started and out of the bind. Could use it on one of the gas giants like Jupiter too.

 

[Hielor]

Do we have a propeller you might see on a deep sea diving vessel? No thrust except churning water or atmosphere? Just to get started and out of the bind. Could use it on one of the gas giants like Jupiter too.

If your propeller is developing 0 thrust, you won't go anywhere...

 

[tylor2000]

Rocket engines will not develop thrust with the high-pressure atmosphere, a 0-thrust propeller would be useless.

Propellers don't use thrust. They use lift. Therefore a 0-thrust propeller is not useless.

 

[Linguofreak]

Rocket engines will not develop thrust with the high-pressure atmosphere, a 0-thrust propeller would be useless.

Huh? The guy's talking about propellers and you start talking about rockets?

Now, granted, I'm not sure that a propeller would really help any (it would just add weight and foul up the aerodynamics at supersonic speeds), but it would certainly work at low speeds in a high pressure atmosphere.

@Tylor2000

As I said, propellors would be a bad idea, because they'd foul up the aerodynamics at supersonic speeds, such as during launch and reentry.

 

[Hielor]

Propellers don't use thrust. They use lift. Therefore a 0-thrust propeller is not useless.

Um, what?

Are you talking about a propeller such as the kind used by boats or prop-driven planes or helicopters?

Yeah, those generate thrust. In a helicopter, the thrust generated by the rotor is used to oppose gravity.

If a propeller generates no thrust, then it's not doing anything at all, and is therefore useless.

uh? The guy's talking about propellers and you start talking about rockets?

He proposed using a "no thrust" propeller for "churning water or atmosphere" to get "out of the bind."

If your propeller generates no thrust, then you're not moving anywhere, and the rocket engines still won't be able to do anything.

I assumed that he was talking about using propellers as an auxilliary for rocket mains, which doesn't do you any good if the propellers aren't doing anything but flinging air around...

 

[tylor2000]

Huh? The guy's talking about propellers and you start talking about rockets?

Now, granted, I'm not sure that a propeller would really help any (it would just add weight and foul up the aerodynamics at supersonic speeds), but it would certainly work at low speeds in a high pressure atmosphere.

@Tylor2000

As I said, propellors would be a bad idea, because they'd foul up the aerodynamics at supersonic speeds, such as during launch and reentry.

That's true. But they could be detachable. I was wondering because this made me think of my idea of using them for jupiter and such...so I asked if they existed.

You could use them for flights like going into venus and such.

---------- Post added at 05:13 PM ---------- Previous post was at 05:01 PM ----------

........

 

[Linguofreak]

He proposed using a "no thrust" propeller for "churning water or atmosphere" to get "out of the bind."

Sorry, I misparsed your response to him. The way you combined your statements about rockets and propellers made me think you were talking about propellers as if they were rockets.

Anyways, I think he's thinking that the force generated by a propeller is something other than thrust, because of the fact that it's generated in a different way than in a rocket engine. I don't get the impression that he thought the propeller wouldn't exert a force, just that the force exerted wouldn't qualify as "thrust". I think he thinks its "lift" instead of "thrust" because it's generated by the Bernoulli effect.

@tylor2000

"Thrust" is any force exerted upon the vehicle by its engines, regardless of the direction of that force or the means by which it was generated (propeller, jet engine, rocket, whatever).

"Lift" generally refers to any force generated by an aircraft's wings perpendicular to the direction of motion, especially when such force is in an upward direction. It can also refer to upward forces on the aircraft from other sources than the wings, such as thrust from the engines.

While the thrust from a propeller is generated by the same mechanism as lift, it is not generally considered to be "lift," except in cases like that of a helicopter.

 

[tylor2000]

Yes, I was talking about using them as auxiliry.

---------- Post added at 07:02 PM ---------- Previous post was at 06:52 PM ----------

Sorry, I misparsed your response to him. The way you combined your statements about rockets and propellers made me think you were talking about propellers as if they were rockets.

Anyways, I think he's thinking that the force generated by a propeller is something other than thrust, because of the fact that it's generated in a different way than in a rocket engine. I don't get the impression that he thought the propeller wouldn't exert a force, just that the force exerted wouldn't qualify as "thrust". I think he thinks its "lift" instead of "thrust" because it's generated by the Bernoulli effect.

@tylor2000

"Thrust" is any force exerted upon the vehicle by its engines, regardless of the direction of that force or the means by which it was generated (propeller, jet engine, rocket, whatever).

"Lift" generally refers to any force generated by an aircraft's wings perpendicular to the direction of motion, especially when such force is in an upward direction. It can also refer to upward forces on the aircraft from other sources than the wings, such as thrust from the engines.

While the thrust from a propeller is generated by the same mechanism as lift, it is not generally considered to be "lift," except in cases like that of a helicopter.

As I understand "thrust" it means you are using a fuel or propellent and using that fuel or propellent to cause particles to exit at high velocity.


With lift you are just climbing thru the air.

 

[Hielor]

As I understand "thrust" it means you are using a fuel or propellent and using that fuel or propellent to cause particles to exit at high velocity.

Which is exactly what you're doing with a propeller--except that the particles you're causing to "exit at high velocity" are just the air that's being pushed backwards by the propeller.

http://www.av8n.com/how/htm/4forces.html

 

[Linguofreak]

As I understand "thrust" it means you are using a fuel or propellent and using that fuel or propellent to cause particles to exit at high velocity.

"Fuel" is your source of energy.

"Propellant" is what you're pushing against to make yourself move forward.

Neither fuel nor propellant has to be on board, but they can be.

"Thrust" is the force you get from using energy from your fuel to push against your propellant.

When you're walking, your fuel is your food, and your propellant is the ground.

In an electric train, your fuel is whatever the local electrical plant is using, and your propellant is the tracks.

In a propeller driven aircraft, your fuel is gasoline, and your propellant is the air that goes through your propeller.

In a rocket with chemical fuels, you burn your fuel to get energy, and use that energy to fling the fuel out the back, so your propellant and fuel are the same.

There are also certain types of rocket (such as nuclear thermal rockets), that have separate fuel and propellant: In a nuclear thermal rocket, you use a nuclear reactor to heat your propellant. So your fuel is whatever the reactor is using, and your propellant is something like hydrogen or methane.

 

[Tommy]

Thrust, as the term is used in aviation/spaceflight, is one of the four cardinal forces (the others being drag, lift, and gravity). ANY motive force is thrust, even powered wheels on landing gear (if there was such a thing) while on the ground. Level flight is achieved when all four forces are balanced.

These forces operate in seperate "frames of reference", especially during re-entry with a high AoA. Thrust is relative to the attitude of the ship and it's thrusters. Unlike airplanes, it is not always in line with the fore-aft axis. Retro thrust, and hover thrust are typically opposed and perpendicular, respectively.

Drag is referenced to the velocity vector, to the rear.

Gravity, of course, is referenced to the gravity source, and is "down".

Lift gets a bit complex, as it can be referred to in two ways. Sometimes lift refers to the wing's lift, which is referenced perpendicular to the wing. During high AoA flight, lift is often referrenced as being a force perpendicular to the velocity vector, or sometimes referenced as "up".

To make things even more confusing, many reference books explain lift and gravity as purely vertical forces, and thrust and drag as purely horizontal forces.

 

[tylor2000]

Oh, I see how you guys are looking at it. Thanks Tommy. I can respect that. I wonder if aviation uses it like that for simplicity or for a standard for instruction or if that is something which is standard in Physics as well.

Well just so know you could probably make a propeller in orbiter which by making a special airfoil that would solve problems like this because it no longer depends on ISP or the thruster definition but rather by creating lift that propels you forward. At least as far as I can tell from reading 2009 beta APIs.

 

[Tommy]

Propeller driven craft can be simulated by a vessel's module now, by doing the math and using addforce. And yacht's have collapsable low drag propellers whidh could, in theory, be enlarged and also made retractable. However, there is still a problem with the huge drag in that atmosphere.

I think a disposable balloon would be workable, let it lift you up to thinner air so the rockets work better, and release. You would drop a bit until you got airspeed, so you'ld have to be high enough before releasing.

If you just want someplace to go on Venus to make the trip interseting, check out Artlav's Shukra base, which is suspended from balloons over Venus.

 

[Hielor]

Oh, I see how you guys are looking at it. Thanks Tommy. I can respect that. I wonder if aviation uses it like that for simplicity or for a standard for instruction or if that is something which is standard in Physics as well.

Aviation uses it like that because that's what it means...

Well just so know you could probably make a propeller in orbiter which by making a special airfoil that would solve problems like this because it no longer depends on ISP or the thruster definition but rather by creating lift that propels you forward. At least as far as I can tell from reading 2009 beta APIs.

I'm fairly sure that you wouldn't be able to make the airfoil on a propeller move through the air in any meaningful fashion that would allow Orbiter to natively simulate a propeller. To simulate a propeller you'd probably be better off having a rocket on which you control the thrust parameters in order to simulate the thrust generated by a rotating propeller -- it's not particularly accurate and it would be terribly hard to code, but I think that's the best we'd be able to do at this point.