What are advantages and disadvantages of powered landing (future Dragon) and aerodynamic (Space Shuttle, Dream Chaser) landing types?
Quote from: Archer on 02/21/2012 07:29 pmWhat are advantages and disadvantages of powered landing (future Dragon) and aerodynamic (Space Shuttle, Dream Chaser) landing types?Wings are orders of magnitude more efficient at generating lift than rocket fuel and engines are.
Over long distances, maybe. But not for small amounts of lift just for landing, especially if you have the rocket engines and tanks and everything anyway.
Quote from: Robotbeat on 02/22/2012 03:20 amOver long distances, maybe. But not for small amounts of lift just for landing, especially if you have the rocket engines and tanks and everything anyway.In that case, nearly all of the delta-V comes from aerodynamics, and that's because wings (even they they are low-aspect-ratio ones like capsules) are more efficient than rocket fuel and engines.
The trade is pretty close, though. Different folks are trying it different ways. I still sort of side with the vertical landing folks... Wings are dead weight in space.May the best design win!
One advantage of wings that has been mentioned is a potentially softer landing for ISS crew after 6 months on orbit. The Soyuz landing is pretty brutal.
Away from Earth, wings are a disadvantage almost all the time. SpaceX wants to have Mars capable hardware and systems (as much as possible).
Quote from: go4mars on 02/22/2012 11:14 amAway from Earth, wings are a disadvantage almost all the time. SpaceX wants to have Mars capable hardware and systems (as much as possible). I am taking the title of the thread to mean aerodynamic landing on Earth. There are other threads for discussing Mars landing techniques.
But there's no reason a powered landing can't be gentle -- consider the Apollo LM, for example.
...for extremely high Mars entry speeds, wings with their higher hypersonic lift/drag (used "negatively") can help keep the entry craft from skipping off into space. But that's a pretty extreme example.
Quote from: Robotbeat on 02/22/2012 04:03 pm...for extremely high Mars entry speeds, wings with their higher hypersonic lift/drag (used "negatively") can help keep the entry craft from skipping off into space. But that's a pretty extreme example.It is. And wings cannot be used for landing on Mars by themselves, of course. So I hold to my point that if we are talking about aerodynamic landing (I take that to mean winged landing, not parachutes), we are talking about landing on Earth. (OK, we might mention Titan, in which case we might make the lander a seaplane. Aerodynamic maneuvering is a different matter and can in principle be carried at any Solar System body (excluding the Sun!) which has an atmosphere.
Don't think anyone mentioned this yet, but wings are pretty reliable compared to rocket engines. Wings are simple chunks of metal with few moving parts, whereas rockets are complicated chunks of metal with lots of moving parts.
Quote from: antiquark on 02/22/2012 06:29 pmDon't think anyone mentioned this yet, but wings are pretty reliable compared to rocket engines. Wings are simple chunks of metal with few moving parts, whereas rockets are complicated chunks of metal with lots of moving parts. On the other hand it's easier to design for engine-out than for wing-out.
{snip}Another is that wings are generally pretty heavy and are only really very good at returning from LEO. Do we really want to be restricted to only returning from LEO?
The title asks:"What are advantages and disadvantages of powered and aerodynamic landing?"One of the advantages of powered landing (vs aerodynamic) is that it can be done at places other than Earth. To artificially exclude the rest of the solar system is to deny one of powered landing's best advantages. We're going to have to get good at powered landing anyway.Another is that wings are generally pretty heavy and are only really very good at returning from LEO. Do we really want to be restricted to only returning from LEO?
It's a trade that depends on many factors and one that definitively will not be answered on this thread.
...I am not artificially excluding the rest of the Solar System. The title "What are advantages and disadvantages of powered and aerodynamic landing?" is meaningless applied to bodies without an atmosphere. Such bodies are automatically excluded from such a discussion. And of course we are going to have to use powered landing for them.
What are advantages and disadvantages of powered landing (future Dragon) and aerodynamic (Space Shuttle, Dream Chaser) landing types?For example, let's assume I have a factory at LEO , and I need to transport product from LEO to Earth, and also to move workers up and down (just a thought experiment).
This looks extremely difficult for a whole variety of reasons. I can see the first and second stages having enough fuel left to make the return journey, but I can't imagine that there would be enough room in the Dragon for the fuel required for powered descent.
I thought they would go with a combination of parachutes to slow Dragon, then the Super Dracos for the last 30 or 40 thousand feet.
BTW: Has there EVER been a spacecraft that has returned from Earth orbit using powered descent all the way to the surface?
Quote from: douglas100 on 02/22/2012 11:05 amOne advantage of wings that has been mentioned is a potentially softer landing for ISS crew after 6 months on orbit. The Soyuz landing is pretty brutal.But there's no reason a powered landing can't be gentle -- consider the Apollo LM, for example.
Soyuz 1 hit the ground at less than 100mph with tangled drogue and reserve 'chutes. So if it's only terminal velocity you have to break against, you're probably talking about less than 10% of the re-entry mass needing to be propellant, wings would weigh more than that, heat shield is still required with both methods.
IIRC I saw a web page that described some early designs of the Russian shuttle before it was decided to use the Buran design.The preferred design was a lifting body that used rockets for landing, I'll try to find it again.
Thank you for your answers!I was thinking about transportation between factory in LEO (space station in LEO) and Earth, not other planets (I cannot imagine why we will have a lot of traffic from other planets/Moon soon).Actually, I was trying to find out what types goods can be manufactured in space, which would justify such venture.Surprisingly, I couldn't find any information about how much would be price of kg of something transported from LEO to Earth. It seems that nobody ever made even a paper-spacecraft, designed to bring goods from orbit to surface; spacecraft that is designed to be launched empty (and refueled in orbit if it uses powered landing), and return with cargo.With current launch prices, I guess, only mining gold and platinum from asteroids will close the business case, but if the price can be less than 100$ per kg down, we have more options.
The first thing to manufacture in space is perhaps spacecraft. After all - they are so valuable that it is worth the cost of launching them to orbit.Steve
As for thought experiment of a factory in space. I am guessing you mean something which doesn't high volume- making drugs or something with low mass but is valuable. So perhaps 10 tons per year shipped to earth per year? With increase possible, perhaps to say 100 tons per year?
If whatever you shipping from space to earth surface can withstand high gees- it's cheaper. 50 gees is a car accident. If payload can withstand over 100 gees, "landing" is more like a controlled crash. A controlled crash into a lake, could something with fairly high terminal velocity. And one major aspect is the accuracy of hitting say 10 sq kilometer area.Normally, one want re-entry which is lifting body- to reduce gees [and heat- though heat isn't as challenging as gee loads].
The first thing to manufacture in space is perhaps spacecraft. After all - they are so valuable that it is worth the cost of launching them to orbit.
One advantage of aerodynamic landing [ from LEO ] is that it has actually been done before.
I wouldn't call what Soyuz does a powered landing. The solid retrorockets fire only a metre above the ground. It's more an impact attenuation device like an air bag. (And its failure means a very hard but not fatal landing.) A powered landing would be something like DC-X or the Masten or Armadillo vehicles. And savuporo is right: that kind of manned landing hasn't been done yet.
I wonder what the trade of propulsive vs autogyro (with and without tip rockets) would look like these days.
These are interesting links.
As far as rotors are concerned, I believe there was a proposal in the early days of designing Vostok to use deployable rotors to land the capsule. This idea was quickly abandoned in favour of a parachute.
The only serious proposal to use rotors all the way through the atmosphere to landing was Roton. I'll say no more about that: there are posters on this forum with far more knowledge about Roton than me.
The capsule that converts into a lifting body seems like a bad idea. It is needlessly complex both in design and operation. Compare it with the simplicity of the CST-100 or Dream Chaser.
No comment about the "UFO" shape!
Again, very interesting links. (You learn stuff on this forum!)
So I should have said: "the only serious proposal to use rotors all the way through the atmosphere to landing that I know of is Roton."
The use of rotors is very attractive but the engineering challenges to using them to land a spacecraft seem formidable. Do you have the rotors extended in some way through the whole re-entry like Roton, or do you deploy them at low Mach numbers just before landing?I've only glanced at the stuff you linked. Have studies been made where the rotors are exposed to re-entry heating? If you wish to avoid that and deploy the blades just before landing, how mechanically complicated would that be? And how safe would that be compared with ordinary parachutes?
Of course as has been said before the original "question" can be answered quite simply with a simple; "Well, that all depends...." at which point you have to get down into the nitty-gritty of what you WANT out of the design in the first place
Ineresting links, thank you. Sounds very complicated though.
RanulfCQuoteOf course as has been said before the original "question" can be answered quite simply with a simple; "Well, that all depends...." at which point you have to get down into the nitty-gritty of what you WANT out of the design in the first place At the first place I want lowest price for bringing goods from LEO down to Earth surface)
I believe such a device was discussed somewhere but I can't remember where. In principle there seems no reason why it shouldn't work, but in the big bad world of real engineering, that's a different matter...
Quote from: douglas100 on 07/24/2012 01:21 pmI believe such a device was discussed somewhere but I can't remember where. In principle there seems no reason why it shouldn't work, but in the big bad world of real engineering, that's a different matter...It was done on the X-38, with electric actuators...
It is done for landing military payloads as well, I think usually with a sort of pneumatic "muscle" device.
Quote from: Robotbeat on 07/24/2012 05:25 pmIt is done for landing military payloads as well, I think usually with a sort of pneumatic "muscle" device.I though that these guys used regular servos.