Comparison of landing methods for capsules, boosters or probes

[Nibb31]

I prefer lifting body design, because it is the most passive method, which involve basically no moving/active part, which reduce the chance of it failing.

A lifting body, just like a spaceplane, requires control surfaces, hydraulics, electronics, and some sort of deployable landing gear. It has a lot more moving/active parts than parachutes or powered landing.

[RainDreamer]

A lifting body, just like a spaceplane, requires control surfaces, hydraulics, electronics, and some sort of deployable landing gear. It has a lot more moving/active parts than parachutes or powered landing.

If those things fail, can the body still at least do unpowered glide through the atmosphere to slow enough speed for secondary landing methods like parachute to be used, or even a landing? I mean the design should be aerodynamically stable right? I also like the heli wings for that, since it can slowdown unpowered, even if electronics fail and there is a total loss of control. Though the spinning might not be really good for an astronaut, so probably better for unmanned probe.

And parachute is probably still the best way to slow down to landing unpowered, uncontrolled, as long as it opened properly. I think we won't stop using parachute for a long time, due to how simple yet reliable it is, despite its other disadvantages.

Edited March 15, 2015 by RainDreamer

[K^2]

If those things fail, can the body still at least do unpowered glide through the atmosphere to slow enough speed for secondary landing methods like parachute to be used, or even a landing?

Depends on a whole bunch of things, including failure modes of things that can fail. But in principle, one could design a lifting body capable of passive re-entry. Landing without controls or landing gear, though, that's just not going to happen.

[Nibb31]

If those things fail, can the body still at least do unpowered glide through the atmosphere to slow enough speed for secondary landing methods like parachute to be used, or even a landing?

Lifting bodies are less stable than winged vehicles. They have a lower lift/drag ratio, and require flaring manoeuvers to break their speed. Without control surfaces that's not going to happen, and you are going to come in too fast and too steep.

Note that capsules are technically lifting bodies, because they are designed to have a positive lift/drag ratio. Yes, they can reenter passively, but without parachutes for the last part of the landing, they're dead too.

[Pipcard]

How is SpaceX going to control their Dragon V2 in order to make it land precisely from orbit? Just with the minimal lift from the capsule along with RCS thrusters?

Edited March 15, 2015 by Pipcard

[RainDreamer]

And a lot of math.

[Airlock]

How is SpaceX going to control their Dragon V2 in order to make it land precisely from orbit? Just with the minimal lift from the capsule along with RCS thrusters?

Yes, and they will use a moveable ballast sled to control the angle of attack.

http://science.house.gov/sites/republicans.science.house.gov/files/documents/HHRG-114-SY16-WState-GReisman-20150227.pdf

its 16 Draco thrusters provide fault tolerant roll control during reentry for precision guidance on course for a soft touchdown on land. Additionally, a movable ballast sled allows the angle of attack to be actively controlled during entry to further provide precision landing control.

[AngelLestat]

I add lithobraking, there is other method or info that I still miss?

It Dependsâ„¢

the question was rephrased.

I prefer lifting body design, because it is the most passive method, which involve basically no moving/active part, which reduce the chance of it failing.

Maybe that is why is the only method which does not need a backup. But in my opinion, the deltav lost it in the ascent plus design things which they need to be taken into account, counter many of their pros.

Heli-wings are pretty nice and would be my secondary choice, if not for it being almost impossible for manual control due to the pod spinning along with the astronaut in it - it will be very disorientating. And if there are mechanisms to allow it to spin without taking the whole pod to a spin, then those mechanism may fail to spin.

The capsule does not spin, if it does it will be very easy to counter with tiny control surfaces.

Helicoters spin (without tail rotor) due engine torque against the wind. But this is a very different case, the capsule mass vs blades is a lot higher, the rotation comes from the wind and the rotor friction against the capsule is negligible.

You can see the autorotation videos in helicopters that I post, which they can guide and land the helicopter without main and tail rotor.

If those things fail, can the body still at least do unpowered glide through the atmosphere to slow enough speed for secondary landing methods like parachute to be used, or even a landing?

As k2 points, in reentry; control surfaces or wings does not work, you need a passive way to mantain the spacecraft oriented without waste much rsc, but without control surfaces once you are at low height, there is not passive design which can save you.

Of course control surfaces failures are very weird, airplanes depends on them all the time.

Also if someone goes through so many difficulties to have a lifting body design, then what is the point to include a backup landing method.

Edited March 15, 2015 by AngelLestat

[Pipcard]

Yes, and they will use a moveable ballast sled to control the angle of attack.

http://science.house.gov/sites/republicans.science.house.gov/files/documents/HHRG-114-SY16-WState-GReisman-20150227.pdf

That's a great idea, changing the center of gravity.

I was thinking of body flaps, like on the Japanese space tourism SSTO concept "Kankoh-maru"

(note that Kankoh-maru would have been 18 meters in diameter and able to carry 50 people)

Edited March 15, 2015 by Pipcard

[Bill Phil]

How is SpaceX going to control their Dragon V2 in order to make it land precisely from orbit? Just with the minimal lift from the capsule along with RCS thrusters?

The superdraco thruster. There's 8 on the V2. They're much more powerful than RCS...

[Superluminaut]

I add lithobraking, there is other method or info that I still miss?

lol, airbags is getting kind off track, in my opinion. Its really more of a touchdown method, as in when you don't have enough data for a fine touchdown. Then again it could be legit on low gravity worlds. Other methods I can think of are also more grey zone type things, like ejecting crew (example vostok 1), or inflating a balloon, but then you wouldn't technically land.

[AngelLestat]

lol, airbags is getting kind off track, in my opinion. Its really more of a touchdown method, as in when you don't have enough data for a fine touchdown. Then again it could be legit on low gravity worlds. Other methods I can think of are also more grey zone type things, like ejecting crew (example vostok 1), or inflating a balloon, but then you wouldn't technically land.

But they may be the main method in some cases, about ballons yeah, I dont think that may count as land (even if you do)

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I found this video from test that Nasa did with heli-blades for the apollo program, the test was good, but discarded due lack of time in developing.

My choices would be:

Manned capsule back to earth

Main method, heli-blades

Backup method, tiny paraglide (wing shape parachute) with 2 seconds solid boosters landing on sea.

Liquid Rocket Booster

The baikal concept use wings and a a breathing air jet engine to return to base which land horizontal.

Not sure what modifications are needed or what different concept may be used to allow main stages to return earth and survive reentry.

Probes:

Well this depends a lot on many things as gravity, atmosphere composition, arrival deltav, surface, etc.

[K^2]

I add lithobraking

Beat 'ya to it.

Of course control surfaces failures are very weird, airplanes depends on them all the time.

There's a lot of redundancy to it on most airplanes. Hydraulics are doubled by mechanical linkages. Trim can be used in lieu of actual control. And even if 2 of 3 DoF totally fail, you can usually use remaining DoF and throttle to have some limited control and line yourself up for a landing. A multi-engine aircraft can be flown by engines alone. Very poorly, but you can line yourself up for a survivable landing.

If you are unpowered, using lifting body design, and surfaces need to be capable of surviving re-entry, your options are far more limited. Redundancy is still your best friend, but there could be weight limitations on making it trully effective.

Honestly, I'd want parachutes as a final fallback for a lifting body vehicle. Even just crew parachutes. Lifting body vehicle can do passive re-entry and descent to safe altitude to bail.

[Sampa]

I think a mixture of both parachutes AND thrusters is better (like the Russian Soyuz capsule)

[AngelLestat]

Beat 'ya to it.

relax, it was commented in the edit reason.

There's a lot of redundancy to it on most airplanes. Hydraulics are doubled by mechanical linkages. Trim can be used in lieu of actual control. And even if 2 of 3 DoF totally fail, you can usually use remaining DoF and throttle to have some limited control and line yourself up for a landing. A multi-engine aircraft can be flown by engines alone. Very poorly, but you can line yourself up for a survivable landing.

If you are unpowered, using lifting body design, and surfaces need to be capable of surviving re-entry, your options are far more limited. Redundancy is still your best friend, but there could be weight limitations on making it trully effective.

Honestly, I'd want parachutes as a final fallback for a lifting body vehicle. Even just crew parachutes. Lifting body vehicle can do passive re-entry and descent to safe altitude to bail.

you mean lifting body + parachute as ESA mini shuttle?

I dont really now why they choose that, it seems like the worse idea ever.

First, you have to deal with this problem:

or the USA variant:

So the added mass of the faring plus the extra volume which cost deltaV in aerodynamics. Normal capsules does not have that problem.

Second, if you get some much trouble to achieve that, why it needs extra parachutes and land in sea???

Just to reentry? That is something that capsules does very well. But this add the parachutes mass plus backup parachutes mass, and it lands on the corrosive sea.

If someone wants to explain me how is that efficient, be my guess.

I think a mixture of both parachutes AND thrusters is better (like the Russian Soyuz capsule)

Dont forget that if you use parachutes, you need also the mass for the backup parachutes. None can be guided.

How´s that will be more efficient than heli-blades with a tiny wing shape parachute as backup?

This option is guided and it requires less mass.

[Sampa]

relax, it was commented in the edit reason.

you mean lifting body + parachute as ESA mini shuttle?

I dont really now why they choose that, it seems like the worse idea ever.

First, you have to deal with this problem:

http://pbs.twimg.com/media/B8cHolgCYAAiM5n.jpg

or the USA variant:

http://www.elektronika.lt/_sys/storage/2014/04/30/Boeing_X-37B_inside_payload_fairing_before_launch.jpg

So the added mass of the faring plus the extra volume which cost deltaV in aerodynamics. Normal capsules does not have that problem.

Second, if you get some much trouble to achieve that, why it needs extra parachutes and land in sea???

Just to reentry? That is something that capsules does very well. But this add the parachutes mass plus backup parachutes mass, and it lands on the corrosive sea.

If someone wants to explain me how is that efficient, be my guess.

Dont forget that if you use parachutes, you need also the mass for the backup parachutes. None can be guided.

How´s that will be more efficient than heli-blades with a tiny wing shape parachute as backup?

This option is guided and it requires less mass.

the efficiency lies in its simplicity. Fewer things to go wrong at the final critical stage of the flight

[AngelLestat]

a parachute deploy seems more complex than a 45 degress change in 3 blades which are extended centrifugally.

first the parachutes needs to be perfectly prepacked, then the top cover needs to shot away with the mini parachute guide to push the others.

Any turbulance or high wind in that moment it may compromise the operation, and you fall without any horizontal control, so you need to choice your location way far from the coast, then you need to add the ship boat recover cost and the parachutes repack in the water. Also the flotation bags and try to eliminate all that possible corrotion from sea water.

if you land in ground, you need to remplace those solid charge which doesn´t give you a so soft landing either. The recovery needs to be in deserts to avoid any problem with ground disparity. So all that recovery also has a cost.

In the other way, you just land in your base with a very soft landing which reduce any possible problem on damage devices in future operations. Which is translated into less money in maintenance, safety checks, tests and faster reusability.

Here there is more information about the rotary capsule.

http://research.jsc.nasa.gov/BiennialResearchReport/2011/82-2011-Biennial.pdf

Edited March 17, 2015 by AngelLestat

[Superluminaut]

a parachute deploy seems more complex than a 45 degress change in 3 blades which are extended centrifugally.

first the parachutes needs to be perfectly prepacked, then the top cover needs to shot away with the mini parachute guide to push the others.

Any turbulance or high wind in that moment it may compromise the operation, and you fall without any horizontal control, so you need to choice your location way far from the coast, then you need to add the ship boat recover cost and the parachutes repack in the water. Also the flotation bags and try to eliminate all that possible corrotion from sea water.

if you land in ground, you need to remplace those solid charge which doesn´t give you a so soft landing either. The recovery needs to be in deserts to avoid any problem with ground disparity. So all that recovery also has a cost.

In the other way, you just land in your base with a very soft landing which reduce any possible problem on damage devices in future operations. Which is translated into less money in maintenance, safety checks, tests and faster reusability.

Here there is more information about the rotary capsule.

http://research.jsc.nasa.gov/BiennialResearchReport/2011/82-2011-Biennial.pdf

I think K^2 meant a parachute as in a landing abort measure.

Here is a question about the rotary method. Wouldn't you eventually need a turbojet to power your rotors at low altitude in order to perform a precision landing?

[Sampa]

for me, my main concern lies in moving parts. For something as critical as a landing system, I believe that the fewer the moving parts the better

[AngelLestat]

we are in the 2015, if we can not deal with a moving part then we are doom.

also.. a parachute deploy can be take it as a moving part.

about how the rotary method land? easy, first you fall at the same speed than a parachute or maybe a bit faster (it all depends on how small are your blades), but when you are close to the ground, you change the pitch of the blades, which transform faster rotation (kinetic energy) into more drag and lift. So you land soft.

Even any helicopter which are not designed for this task, all can land without engines (and they control where it lands without spin or anything).

[Iskierka]

Helicopters have their main and tail rotors mechanically linked, allowing them to retain yaw control through auto-rotation. Can you explain how exactly a single rotor with no correcting torque would avoid spinning the capsule?

[Robotengineer]

I know that if I were an astronaut, I would not want to lithobrake or use the heli-blades. A combination of the two would be particularly nauseating.

[Superluminaut]

about how the rotary method land? easy, first you fall at the same speed than a parachute or maybe a bit faster (it all depends on how small are your blades), but when you are close to the ground, you change the pitch of the blades, which transform faster rotation (kinetic energy) into more drag and lift. So you land soft.

Even any helicopter which are not designed for this task, all can land without engines (and they control where it lands without spin or anything).

This assumes you are coming down right on your target. Capsule reentry is not that accurate, it would require some kind of thruster guidance.

Helicopters can land without power?

[magnemoe]

This assumes you are coming down right on your target. Capsule reentry is not that accurate, it would require some kind of thruster guidance.

Helicopters can land without power?

Emergency landing without power( yes you need backup power to rotate the blades) is pretty standard, in fact its part of any helicopter operations you want to avoid being in an setting auto-rotate can not save you, low and slow but not just a few meter over the ground is most dangerous. High chance modern helicopters enter autorotate mode automatically on engine out.

You then let the rotor spin up, you have an terminal speed and you do an suicide burn by turning the blades to get lift, yes its a bit hairy but less so then letting rockets do the suicide burn.

Most dangerous aspect in helicopter transport to offshore oil rigs is the behavior of helicopter after splashdown, not the landing, it tend to tip over and fill with water.

Multiple ideas here like let it almost sink just let you get the head above the water, oxygen supply, blow out panels instead of emergency exits is some of the ideas.

- - - Updated - - -

Emergency landing without power( yes you need backup power to rotate the blades) is pretty standard, in fact its part of any helicopter operations you want to avoid being in an setting auto-rotate can not save you, low and slow but not just a few meter over the ground is most dangerous. High chance modern helicopters enter autorotate mode automatically on engine out.

You then let the rotor spin up, you have an terminal speed and you do an suicide burn by turning the blades to get lift, yes its a bit hairy but less so then letting rockets do the suicide burn.

Most dangerous aspect in helicopter transport to offshore oil rigs is the behavior of helicopter after splashdown, not the landing, it tend to tip over and fill with water.

Multiple ideas here like let it almost sink just let you get the head above the water, oxygen supply, blow out panels instead of emergency exits is some of the ideas.

You can change your trajectory by moving the rotor, this works far better an RSC in KSP where I can land within 10 meter in atmosphere if I have rcs, I let mechjeb do the landing and give me predictions I can then use RCS to correct trajectory,

[AngelLestat]

Iskierka, Robotengineer, Superluminaut:

Capsule reentry does not need to be so accurate if you use the heli-blade method, it can fall at 15km/h vertital speed but with an horizontal speed of 100km/h "not sure about the real number", that's enough to correct any deviation in the reentry.

Many things was already explained in the topic, here is a recap:

helicopters landing without power:

https://youtu.be/2voCedPQMUo?t=3m

https://youtu.be/E2a9H8Xw8Mo?t=1m47s

You can keep searching videos, is a very common procedure that any pilot should know.

If you still hear the sound of the engine, is just because this is done with students and double command.

When practicing, instead of actually shutting the engine off completely though, they usually just turn the engine down enough to disengage it from the rotor. This way, if the student encounters a problem during a no-power landing, the helicopter can be throttled back up to avoid an accident. Given that this isn’t an option during actual engine failure, it’s critical for helicopter pilots to practice this until they have it down pat.

Helicopters rotates due the engine torque, not because the rotor blades spin.

In fact when helicopters had a problem with the tail rotor, pilots shut down the engine to avoid spin without control, then they land with autorotation.

In the capsule case, the blades rotates due wind, so there is not torque and the rotor friction against the capsule is negligible plus the difference on mass, and to counter it is enoght a very tiny fin in the capsule body.

Here the test in the 60th

With 2 very tiny fins on the side, plus today technology and a pilot, that thing will fly and land better than anything.

Edited March 18, 2015 by AngelLestat