Could a Quadruplane Be Effective on Duna?

[Geschosskopf]

I learn by trial and error

Then why ask for advice?

You asked for advice, I gave you some. And I've probably done more aviating on Duna than 99.9% of the forum members. You won't get better advice than that. If you choose to disregard it, then it's your funeral. Don't say I didn't warn you.

Since I am designing SSTOs, they'll be plenty of delta-v to get back into orbit. I'm only really looking to design an SSTO with enough lift that it merely can land safely on Duna without the use of retroburns. I only need the stall speed around 70 m/s. My last SSTO stalled around 120 m/s, but it wasn't designed to fly on Duna to begin with. This really seems like a simple problem of just adding lift, and I'm trying to do that without big wings so that I can more easily land on rough terrain. I don't plan to fly around the planet cause the game tends to crash after 15 minutes of low altitude flight, so I suspect having to refuel in orbit. Duna to me is still magical cause I've only been on it once, and it was a learning experience, and I don't want to tarnish that with easy mode.

Jet engines don't work on Duna because there's no free-range oxygen. So if you have an SSTO that works on Kerbin, it will assuredly NOT work on Duna. The jets, intakes, and extra LF are just dead weight, and if it can get to LKO, it has way too little wing to fly on Duna.

For the same plane, at most terrain altitudes the stall speed on Duna is about 1.5x as high as on Kerbin because of the thinner air. IOW, if you stall at 70m/s on Kerbin, you'll stall at 100m/s on Duna.

And even landing at 35m/s on Duna needs retro thrust to avoid mishap with any degree of certainty. Airbrakes don't work, wheel brakes don't work, so without retro thrust you bounce along for miles. Sometimes you get lucky and survive this but most times you'll either cartwheel off a bump in the ground or hit a wall.

Oh well, have fun crashing.

[Edax]

Then why ask for advice?

You asked for advice, I gave you some. And I've probably done more aviating on Duna than 99.9% of the forum members. You won't get better advice than that. If you choose to disregard it, then it's your funeral. Don't say I didn't warn you.

Jet engines don't work on Duna because there's no free-range oxygen. So if you have an SSTO that works on Kerbin, it will assuredly NOT work on Duna. The jets, intakes, and extra LF are just dead weight, and if it can get to LKO, it has way too little wing to fly on Duna.

For the same plane, at most terrain altitudes the stall speed on Duna is about 1.5x as high as on Kerbin because of the thinner air. IOW, if you stall at 70m/s on Kerbin, you'll stall at 100m/s on Duna.

And even landing at 35m/s on Duna needs retro thrust to avoid mishap with any degree of certainty. Airbrakes don't work, wheel brakes don't work, so without retro thrust you bounce along for miles. Sometimes you get lucky and survive this but most times you'll either cartwheel off a bump in the ground or hit a wall.

Oh well, have fun crashing.

Even if I learn by trial and error, it's handy to ask for advice for. I can at least make an approximate guess by asking some more experienced people. The reason I disregard some of your advice is that your playing a different game then me, using parts I don't have, and using a play-style I wont adopt. It's nothing personal.

[Geschosskopf]

Even if I learn by trial and error, it's handy to ask for advice for. I can at least make an approximate guess by asking some more experienced people. The reason I disregard some of your advice is that your playing a different game then me, using parts I don't have, and using a play-style I wont adopt. It's nothing personal.

None of which changes the basic facts of flying on Duna, which I spelled out for you. Physics is what it is. How you deal with that, via playstyle, is a matter of taste.

Oh well, I'm sure your widow will look pretty in black

[mikegarrison]

This might be a dumb question, but I'm not fully understanding the purpose of control surfaces on the wings. I put control surfaces at both ends of the space plane so that it can pitch up and down, so what is the function control surfaces on the wings given that their so close to the center of mass? Often times in-game they seen uncooperative, such as 2 sets of controls surfaces on a big-s wing will cause 1 set to increase lift, and the other set to decrease lift (again, on the same wing) when I'm trying to pitch the plane. This doesn't seem to make any sense logically.

For controlled flight you need to control all three axes (pitch, yaw, roll). Roll is typically controlled on the wing. Pitch and yaw are typically controlled at the tail and/or nose.

[Edax]

For controlled flight you need to control all three axes (pitch, yaw, roll). Roll is typically controlled on the wing. Pitch and yaw are typically controlled at the tail and/or nose.

Ohh, I thought the tailplane and reaction wheels would control roll. I suppose that explains why when I don't have control surfaces on the wings that the plane loses stability.

[ajburges]

Ohh, I thought the tailplane and reaction wheels would control roll. I suppose that explains why when I don't have control surfaces on the wings that the plane loses stability.

Yes pitch authority is a function of the torque your control surfaces generate. Torque is a product of force and distance from CoM. Technically any pitch or yaw surface can contribute to roll.

Since drag is proportionate to just force for control surfaces, you want to stick them out as far as possible for efficiency. This means that you typically don't want to use pitch and yaw surfaces for roll because they are too close to the body.

[Edax]

I think I've got a working quadruplane that will stall under 70 m/s at around 10,000m on Kerbin. Now I just have to figure how to get it into space.

Yep, still STTOs, though it's fuel is run to the ragged edge.

Edited August 18, 2015 by Edax