The fascinating problem of starship landing -- No legs

[joek]

In response to the cross-talk in the original thread, this thread is devoted to Starship landing solutions which do not use (or propose to use) landing legs.  If you propose a solution or trades, please be specific as to departure and destination.

edit: sorry, corrected link to original thread.

[Walkerton]

This is for landing on earth.

If they had a large silo built into the ground, maybe 20 meters in diameter.  About 40 meters deep.
Starship will land in the silo.
The silo has huge fans that blow air up the center.  Strong enough to hold up starship.  So once half way in the silo starships raptor is shut off.
Maybe a ground installed raptor would be used, maybe several large jet engines.
The silo also has numerous vents in the side walls, also with big fans.  That keep starship up right, steer it if you will.

edit - or use water instead of air.  Spray it up at Starship as it descends into the silo.  that would also solve the fire problem

[Stan-1967]

This sounds like a more complicated version of catch mechanisms, except you are proposing pneumatic cushioning vs. mechanical methods.   The method has to deal with the material problems of handling Raptor exhaust while simultaneously blowing a column of air up the tube at terminal velocity

[rakaydos]

re: pnumatic "landing"

A raptor has a mass flow of x and an Exaust velocity of Y
Starship has a terminal velocity substantially below Y, but by entraining air, the let exaust velocity drops while the effective mass flow increases.

You probably need a great many raptors in your wind tunnel to get enough updraft to suspend a starship by it's brakerons, but  it should be possible.

[Pahimarus]

This is for landing on earth.

If they had a large silo built into the ground, maybe 20 meters in diameter.  About 40 meters deep.
Starship will land in the silo.
The silo has huge fans that blow air up the center.  Strong enough to hold up starship.  So once half way in the silo starships raptor is shut off.
Maybe a ground installed raptor would be used, maybe several large jet engines.
The silo also has numerous vents in the side walls, also with big fans.  That keep starship up right, steer it if you will.

How do you turn it off?

Presumably you'd need a mechanical system to then grab it so you can shut down the blowers. Seems like it would be simpler to just solve the mechanical cushioning piece for the mechanical catch system you still need.

But points for the, "that would be awesome factor." Maybe Elon would call it the starship bounce house.

[xvel]

This is for landing on earth.

If they had a large silo built into the ground, maybe 20 meters in diameter.  About 40 meters deep.
Starship will land in the silo.
The silo has huge fans that blow air up the center.  Strong enough to hold up starship.  So once half way in the silo starships raptor is shut off.
Maybe a ground installed raptor would be used, maybe several large jet engines.
The silo also has numerous vents in the side walls, also with big fans.  That keep starship up right, steer it if you will.

omg just do the same, land in vertical wind tunel but horizontal, without flip maneuver and raptors, starship has control surfaces already to do exactly that, then soft touchdown on net.

[hoardsbane]

This is for landing on earth.

If they had a large silo built into the ground, maybe 20 meters in diameter.  About 40 meters deep.
Starship will land in the silo.
The silo has huge fans that blow air up the center.  Strong enough to hold up starship.  So once half way in the silo starships raptor is shut off.
Maybe a ground installed raptor would be used, maybe several large jet engines.
The silo also has numerous vents in the side walls, also with big fans.  That keep starship up right, steer it if you will.

omg just do the same, land in vertical wind tunel but horizontal, without flip maneuver and raptors, starship has control surfaces already to do exactly that, then soft touchdown on net.

Interesting thought!

Starship already has the control surfaces for stability ... just needs an updraft of approx 90m/s (terminal velocity).  Could use jets.

Eliminates flip maneuver (still required for Mars though), associated fuel and (problematic) engine relight (and simplify the associated autogenous pressurization). 

Could have a pneumatically damped cradle to perform the final deceleration (and as a safety measure) and to lift the starship back vertical for remounting on the booster.  Cradle with large surface area should prevent any damage to the fuselage or tiles. 

Especially suitable for the tanker version of Starship.  Would potentially simplify the launch tower (if it is planned to have it catch the Starship).  Perhaps could remove the header tanks and associated piping completely.

Starship has already demonstrated good control on descent.

Certainly no more difficult than catching with the launch tower.

Great idea!

[Lampyridae]

The problem is not only creating a fast enough air column to decelerate the Starship but also make the column of air high enough because deceleration happens over a distance. You wind up with a very large structure, at which point you may as well just have a catching cradle that slides down the side of the structure and braking when it grabs the Starship, no giant fans needed.

Since the best way to counteract gravity using airflow is with lift, have the Starship fitted with lifting airfoil cross sections on the flaperons and have it picked up by a cradle running (very fast) on tracks, maybe like a train version of Ms Chief.

[KelvinZero]

Maybe some sort of lighter than air anchored structure that can begin decelerating the starship quite high up? And perhaps with a nose hook instead of a net?

[Oersted]

I'd certainly rather trust my life with a big-@ss net than a flip-and-burn maneuver. Good for Earth but we need legs and flip-burn anyway for Mars, so it will have to be worked out.

[Burningdan87]

I have to say this is one of the more...confusing and hard to take seriously of Elon's musings. The leg system flat out needs to be worked out, and the landing system for Mars and other similar bodies will be the same routine as Earth presumably (moon excluded for now). Even on Earth catching the Starship itself seems like significantly more of an engineering challenge than working out the legs themselves. I understand that it would reduce mass, but with all the rest in mind it seems like this sort of reduction would be worked out after they have the standard legs and landing system worked out. This seems like putting the cart before the horse.

[Lampyridae]

Maybe some sort of lighter than air anchored structure that can begin decelerating the starship quite high up? And perhaps with a nose hook instead of a net?

An aerostat perhaps? Maybe a combination of inflatable and a rotary wing (as in aerofoil gas bags in a propeller form), since the thing is just expected to hover and take a huge load. The technology could eventually be adapted for Venusian spaceports.

However, a big steel construction is still simpler and likely cheaper in the long run - and not dependent on the weather.

I have to say this is one of the more...confusing and hard to take seriously of Elon's musings. The leg system flat out needs to be worked out, and the landing system for Mars and other similar bodies will be the same routine as Earth presumably (moon excluded for now). Even on Earth catching the Starship itself seems like significantly more of an engineering challenge than working out the legs themselves. I understand that it would reduce mass, but with all the rest in mind it seems like this sort of reduction would be worked out after they have the standard legs and landing system worked out. This seems like putting the cart before the horse.

Elon's really pushing the envelope, but this would become relevant in the 1000 flights per year category. Especially for something like tankers. If you take away landing legs and landing propellant, the mass savings are huge. Instead of 100 tonnes to LEO you get 120+ with the same system.

Even just replacing the 20 tonnes of landing propellant with something else, eg bigger flaps, increases the lifespan of the Raptors.

[rsdavis9]

All of the suggestions sound like trying to make a falling starship and convert it into a plane with landing gear and land it on a runway.

Maybe instead of helicopters, giant fans, grabbing hooks we just need a giant flying frame that can cradle the starship in it and then land on a runway.

so basically
A giant rectangle the size of starships outline.
Cradling straps to softly hold starship. Imagine the large boat travel lifts.
Wings on the outside of the frame.
Wheels on the underside of the frame.
Maybe some small engines to fly this thing.
It will fly up to lets say 5km and fly under the starship and gently catch it.
Probably can use props at the speeds we are talking about.

EDIT: So I am callling this concept: Giant flying travel lift.

I cross posted this in the previous thread.

EDIT: EDIT:

I suppose for the catch operation that it would be good to be able sky dive the same as the starship. So have wings/flaps that can move up and down like the startship. So get under starship and then control the fall rate to match the starship. Once in the cradle then lower flaps/wings and with engine power transition into winged flight.

[Lampyridae]

All of the suggestions sound like trying to make a falling starship and convert it into a plane with landing gear and land it on a runway.

Maybe instead of helicopters, giant fans, grabbing hooks we just need a giant flying frame that can cradle the starship in it and then land on a runway.

Why have wings? If  you have enough vertical thrust to null out the Starship descent plus that of the lift platform (say 600 tonnes), then you have enough to touch it down on a pad.

When I say aerofoil, I don't mean wings for runway-velocity landings, I mean keeping the flaperons as they are but giving them a cross section that generates lift efficiently. Right now they are pretty much just slabs. They don't have to provide enough lift at low enough speeds for landing, just enough to turn a fall into a fast, steep glide. Then whatever Rube Goldberg machine snatches it out of the air like the world's most insane Top Gear episode.

[Thunderscreech]

This diverts from the 'horizontal grab' comment, but for the sake of completeness: Have the vehicle land vertically without legs directly onto a mount from which it can launched directly or be lifted onto a Superheavy without being grappled to a crane. 

Delete the legs on Earth in exchange for the same quick turn-around benefits promised during MCT and now again with the grid-fin hangers for the booster.

[rsdavis9]

Why have wings? If  you have enough vertical thrust to null out the Starship descent plus that of the lift platform (say 600 tonnes), then you have enough to touch it down on a pad.

Wings allow unpowered landings because of lift. Unpowered does offer some measure of backup if things go wrong. If you are going to build massive things on the ground for landing things why not go for a proven landing technique on earth.

[Oersted]

It is way to complicated to catch Starship by the whole surface of the ship. Nets can get tangled in the fins and the tiles are no-where strong enough, but will be mauled by a net thus making quick and easy re-use impossible.

If you want to catch Starship it should be by a big hook in the nose. It can fold out like an airplane refuelling receptacle and can be easily snagged by a long cable hanging from a helicopter or other aircraft. Well/known technology, "just" needs to be scaled up. 

[rsdavis9]

It is way to complicated to catch Starship by the whole surface of the ship. Nets can get tangled in the fins and the tiles are no-where strong enough, but will be mauled by a net thus making quick and easy re-use impossible.

If you want to catch Starship it should be by a big hook in the nose. It can fold out like an airplane refuelling receptacle and can be easily snagged by a long cable hanging from a helicopter or other aircraft. Well/known technology, "just" needs to be scaled up.

Or on the pad. The same applies.
Big hook on the leeward side up on the nose.
Grabber arms for lower section to stabilize it upright after it is hooked off center up in the nose.

Remember this thread is "no legs"
Not "no flip burn"
So more inclusive then no "horizontal flip".

I for one like the flip.

[spacenut]

I still think 3-4 large drogue parachutes in the nose area to help flip the Starship a little slower and with a few extra seconds of drag time allow the fuel to settle and the engines to power up correctly.  Release the parachutes and land with the little legs they have. 

Parachute drogues would not be enough to provide a safe landing but just slow down the Starship enough for the fuel to settle.  Kind of like the parachutes used to slow down older fighter planes that couldn't reverse thrust.  The parachutes couldn't stop the plane but just slow it down.  Same with the drogue parachutes.  I even think the Shuttle had a drogue parachute to slow it down on it's unpowered landing.

Now, the parachutes may not work on Mars.  Atmosphere is too thin.  It may have to use the flip and engines.  So this still may have to be mastered.  But, only one engine is needed for Mars landings.  Two seem to be needed for earth landings. 

The other option is high efficiency side thrusters to help settle the fuel before entering engines. 

Another thing is the complete wrap around skirt.  I would think leaving off some skirt material on the leeward side of the Starship, not only would save some weight but allow for engine exhaust to get out from under the skirt at landing.  I know Elon wants the bottom cargo bays, but one or more may have to be sacrificed and just leave the skirt frame. 

[Oersted]

Even better, snag those deployed flip/brake-chutes in mid-air and gently carry the Ship down.