What is the point of landing back on Earth with landing gear?

[sevenperforce]

1 minute ago, Nibb31 said:

SpaceX's CRS proposal involved a mix of V1 and V2 Dragons for cargo depending on requirements. I suspect that they will use V1 for the early flights and try to transition to V2 for missions that don't require CBM berthing. That way they can put the V2 propulsive landing through it's paces on unmanned flights.

I imagine we will see at least one unmanned propulsive landing on a droneship with abort-to-splashdown as an option, followed by a couple of unmanned RTLS landings and then a crewed RTLS landing. 

[Nibb31]

There won't be any crewed RTLS landings because NASA doesn't want any.

[sojourner]

I don't think NASA has totally ruled out RTLS landings though.  I believe they left some room in the contract to eventually allow it. If they approve.

[sevenperforce]

31 minutes ago, Nibb31 said:

There won't be any crewed RTLS landings because NASA doesn't want any.

NASA is not necessarily the only supplier of astronauts. 

[Nibb31]

For the foreseeable future, they pretty much are SpaceX's only possible customer for manned flight, and the ISS is pretty much the only place where Dragon can go.

Wake me up when another customer pops up.

Edited March 16, 2016 by Nibb31

[Nothalogh]

1 hour ago, Nibb31 said:

For the foreseeable future, they pretty much are SpaceX's only possible customer for manned flight, and the ISS is pretty much the only place where Dragon can go.

Wake me up when another customer pops up.

What's to say SpaceX doesn't do it with their own people? NASA be damned.

Edited March 17, 2016 by Nothalogh

[Nibb31]

What would be the point, other than wasting money?

SpaceX is a commercial launch provider, not a space agency.

[sevenperforce]

5 hours ago, Nibb31 said:

What would be the point, other than wasting money?

SpaceX is a commercial launch provider, not a space agency.

I'm not sure whether anyone told Elon this. He may be under a different impression. 

But in all seriousness, I don't see why SpaceX wouldn't conduct a few manned flights independent of NASA. They seem to have big plans for the Dragon platform and will want to demonstrate flexibility and independence from NASA. The trunk on the Dragon V2 is large enough to carry a small sat for deployment to offset launch costs. 

There's got to be some market for human spaceflight. Obviously there will be the handful of tourist launches: four or five people willing to drop 25 million each to spend a few hours in orbit, etc. Can't expect those to last, though. Surely there's some other reason....

[PB666]

On 3/15/2016 at 8:42 PM, sevenperforce said:

Splashdown requires recovery by ship, which is costly and requires a ton of infrastructure and support. The Soyuz capsule parachutes to land...but it actually requires its own set of solid-fueled retrorockets mounted on the parachute cables to slow down at the very end. A parachute which actually slows down a 7-tonne capsule to a gentle landing speed would be absolutely massive and extremely heavy. If the retros on the Soyuz fail, you live, but you break most of your teeth and possibly your spine.

The Dragon V2 uses the landing rockets as an emergency launch abort system as well, saving weight at launch. Most capsules have had an external abort tower that is discarded every mission it isn't used. 

The landing legs soften touchdown and will probably collapse/crush in the event of a parachute landing on land, destroying themselves in the process but saving the occupants. 

On a car they have the collapsable bumper that shifts energy to the frame, they are fairly cheap structures but the protect basically everything in back of the radiator. They are cheap, for a good size rocket they could be 1000$ each, 4 would suffice, and you can send them to the scap yard when done. you don't even need to have extensions just outmount them and put a heat shield on one side.

So here is the basic problem with parachutes

Lets say terminal velocity if 60m/s when drag is x.

You add a parachute that creates drag of 2X, terminal velocity is not 30 m/s but 43 m/s

You add another parachutes (total = 2) and bring drag to 4x, terminal velocity drops, however to 30 m/s

You add two more parachutes (total = 4) terminal velocity drops to 22 m/s

you add 4 more parachutes (total  = 8) terminal velocity drops to 15 m/s

You now have to quadruple the size of each parachute (total (Mega) = 2)

you add 6 more parachutes and the terminal velocity drops to 7.5 m/s (~17 miles per hour).

you now have to quadrupel the size of each parachute again (total (superMega) = 2)

you add 6 more parachutes and the terminal velocity drops to 3.75 m/s (~8 miles per hour)

you now have to quadrupel the size of each parachute again (total (UltraMega) = 2)

you add 6 more parachutes and the terminal velocity drops to 1.8 m/s (~4 miles per hour)

So the deal is that if you have a strut that can reduce the highest moment of acceleration by 80%, what you can do is reduce the size of the parachute by 16 fold. The second thing is that if you land with a parachute only, your vehicle will tip over unless you increase the radius of at least 3 points in contact with the ground (4 is better because with 3 points the smallest radius is the 0.5 whereas with 4 legs the smalles radius is 0.707 the largest). The reason for this is that the parachute equilibrates the ship to the horizontal velocity of the airstream which is never zero and when you have a very hot device in that airstream it will create its own local (usually chaotic) winds, as a result you have horizontal vectors when the vessel touches the ground. Its a good idea to have both struts and manuevering thrusters for landing back on earth. 

Dont the russians use mouth guards for protecting the teeth? I thought each astronaut was molded into a special cocoon seat for lift-off and landing, in order to protect him in case of a hard landing.

 

 

 

[Nibb31]

2 hours ago, sevenperforce said:

I'm not sure whether anyone told Elon this. He may be under a different impression. 

I'm pretty sure Musk knows what he can do and he wants to do. I just wish that the SpaceX fanboys would understand that SpaceX is not a space program. It doesn't compete against NASA. It only exists because of money that comes from NASA.

Musk doesn't have infinite money. He can't throw billions out the window just to prove a point. As a billionnaire, most of his money is tied up in his corporate investments. If he's like most billionnaires, he actually borrows money for his daily expenses because of that.

2 hours ago, sevenperforce said:

But in all seriousness, I don't see why SpaceX wouldn't conduct a few manned flights independent of NASA. They seem to have big plans for the Dragon platform and will want to demonstrate flexibility and independence from NASA. The trunk on the Dragon V2 is large enough to carry a small sat for deployment to offset launch costs. 

And here I was thinking that they had big plans for Mars, not LEO. Hint: Dragon has no purpose for Mars. It's a LEO taxi, and turning it into something that it isn't is like turning a car into a super tanker.

Musk wanted a nice shiny spaceship, so that's what he got. That doesn't mean that there is a market for it. For the moment, the only market  for Dragon is NASA flights to the ISS. There are simply no other customers.

If an actual customer appears, I might reconsider, but until then, Dragon ends when the CCDev program ends.

2 hours ago, sevenperforce said:

There's got to be some market for human spaceflight. Obviously there will be the handful of tourist launches: four or five people willing to drop 25 million each to spend a few hours in orbit, etc. Can't expect those to last, though.

Obviously? 25 million for a few hours is really expensive. You could stick around a day or two, but I suspect that floating around a Dragon cabin would get boring after a few orbits. And there is no toilet...

2 hours ago, sevenperforce said:

Surely there's some other reason....

Surely there is. But we have been waiting for 50 years for someone to find such a reason to send people to space. I suspect we will have to wait a while longer...

[sevenperforce]

1 hour ago, PB666 said:

On a car they have the collapsable bumper that shifts energy to the frame, they are fairly cheap structures but the protect basically everything in back of the radiator. They are cheap, for a good size rocket they could be 1000$ each, 4 would suffice, and you can send them to the scap yard when done. you don't even need to have extensions just outmount them and put a heat shield on one side.

Cheap? Sure. Lightweight? Not so much. Shock-absorbing landing legs work much better and are lighter.

1 hour ago, PB666 said:

So here is the basic problem with parachutes...

Here is the basic problem with parachutes.

F = c*A*v²

This is the (simplified) drag equation. F is force, A is area, v is velocity, and c is the applicable drag constant. Setting force equal to m*g and rearranging, we find the terminal velocity equation:

v = [(m*g)/(c*A)]^1/2

This is the problem. Terminal velocity is proportional to the inverse square root of your parachute's area, so each time you want to cut your velocity in half, you have to quadruple the area of your parachute. Plus, it's actually worse, because you have to factor in the mass of your parachute:

v = [((m+d*A)*g)/(c*A)]^1/2

In this equation, d is the cross-sectional density of your parachute. So, the curve ends up looking like this:

You'll have a parachute that weighs more than your payload before you get down to a safe landing velocity.

1 hour ago, Nibb31 said:

I'm pretty sure Musk knows what he can do and he wants to do. I just wish that the SpaceX fanboys would understand that SpaceX is not a space program. It doesn't compete against NASA. It only exists because of money that comes from NASA.

And because of money that comes from comsat operators.

1 hour ago, Nibb31 said:

And here I was thinking that they had big plans for Mars, not LEO. Hint: Dragon has no purpose for Mars. It's a LEO taxi, and turning it into something that it isn't is like turning a car into a super tanker.

Musk wanted a nice shiny spaceship, so that's what he got. That doesn't mean that there is a market for it. For the moment, the only market  for Dragon is NASA flights to the ISS. There are simply no other customers.

The unmanned Dragon V2, mounted on Falcon Heavy, is intended to deliver payloads to the surface of Mars without modification.

1 hour ago, Nibb31 said:

We have been waiting for 50 years for someone to find such a reason to send people to space. I suspect we will have to wait a while longer...

We've also been waiting fifty years for a way to get people into space and back for less than $60 million+ per seat. Dragon V2 cuts that in half, or better. Dragon V2 is about ten times cheaper than the Shuttle flights were. If the price comes down enough, previously unprofitable reasons to send people to space become profitable.

Not that I know what those reasons are.

Here's a idea, though. Many companies use subsidiaries or shell corporations to purchase small slices of land in small countries with financial secrecy, allowing them to use those countries as tax havens. Because most countries will offer tax exemption if you can show that you have already paid taxes to another entity (to prevent double taxation), this can be hugely profitable when large assets need to be transferred. In Germany, for example, the amount of German-owned assets in international tax havens is roughly a fifth of the country's GDP.

Of course, the local government controlling the jurisdiction is able to control what goes on and what the local tax rates are. It can also set the bar for entry in such a way that only large corporations can afford to utilize the tax benefits.

I wonder whether it would be profitable for an independent company to set up an orbital server to conduct currency exchange, banking operations, asset transfer, investment brokering, and a variety of other operations outside of the jurisdiction of any government. The operating company wouldn't be doing the operations themselves, of course; they would lease server space/time to individual banks and other companies. An orbital server would be able to accommodate a ton of traffic without incurring additional overhead, enabling it to offer space to numerous smaller entities which wouldn't be able to get space in a tax haven.

Such a server would likely need regular servicing/updating for a variety of reasons, beyond what would be possible to do automatically. So they would need some kind of short-term hab.

Assuming that the servers and an inflatable hab could be lofted with a single Falcon Heavy launch and imagining a ten-year lifetime with manned servicing missions every six-eight months, we're looking at a total cost of roughly $2.5 billion, plus the cost of the server/hab itself. I wonder if an orbital server like that could earn more than $250 million per year.

[Nibb31]

19 minutes ago, sevenperforce said:

And because of money that comes from comsat operators.

Yes, with a discount. Which is possible because Falcon and Merlin development was partially paid for by NASA. Dragon is fully paid for by the CCDev and CRS programs.

Without NASA, there would be no SpaceX.

Quote

The unmanned Dragon V2, mounted on Falcon Heavy, is intended to deliver payloads to the surface of Mars without modification.

No, that isn't what it is intended for. It's intended as a LEO taxi. There are a couple of paper studies to turn it into something else, but those will need quite some engineering and of course, a customer, which doesn't exist yet.

Quote

We've also been waiting fifty years for a way to get people into space and back for less than $60 million+ per seat. Dragon V2 cuts that in half, or better. Dragon V2 is about ten times cheaper than the Shuttle flights were. If the price comes down enough, previously unprofitable reasons to send people to space become profitable.

What unprofitable reasons ? Even if you bring the price of the seat down to $10 million, which isn't realistic any time soon, it still won't spring new demand. There is still no destination in LEO and a cheap Dragon would still be a bridge to nowhere.

Space flight is an extremely inelastic market.

Quote

I wonder whether it would be profitable for an independent company to set up an orbital server to conduct currency exchange, banking operations, asset transfer, investment brokering, and a variety of other operations outside of the jurisdiction of any government.

They could just put their servers on an abandoned oil platform in international waters. It would offer the same safe haven for a fraction of the price. Ever heard of Radio Caroline ?

Quote

Such a server would likely need regular servicing/updating for a variety of reasons, beyond what would be possible to do automatically. So they would need some kind of short-term hab.

No it wouldn't. It would be cheaper to just launch a new spacecraft with new servers on it than to launch a manned mission.

Quote

Assuming that the servers and an inflatable hab could be lofted with a single Falcon Heavy launch and imagining a ten-year lifetime with manned servicing missions every six-eight months, we're looking at a total cost of roughly $2.5 billion, plus the cost of the server/hab itself. I wonder if an orbital server like that could earn more than $250 million per year.

An offshore oil rig costs a lot less than that. Or have a chat with the Prince of Sealand.

Edited March 17, 2016 by Nibb31

[sevenperforce]

Then again there is always the Bigelow commercial space station. 

[Nibb31]

2 minutes ago, sevenperforce said:

Then again there is always the Bigelow commercial space station. 

Have they found a customer yet ?

[sevenperforce]

13 minutes ago, Nibb31 said:

Have they found a customer yet ?

Dunno. How are they getting funded now?

[sojourner]

They're not.

[fredinno]

23 hours ago, sevenperforce said:

I imagine we will see at least one unmanned propulsive landing on a droneship with abort-to-splashdown as an option, followed by a couple of unmanned RTLS landings and then a crewed RTLS landing. 

Why a drone ship? You can to RTLS no problem with DragonV2, because that takes no more fuel. It's near the ocean, so they can still abort to the ocean (or if things go bad) just do a parachute landing- cargo should not be as sensitive, just in case that happens.

4 hours ago, Nibb31 said:

Yes, with a discount. Which is possible because Falcon and Merlin development was partially paid for by NASA. Dragon is fully paid for by the CCDev and CRS programs.

Without NASA, there would be no SpaceX.

No, that isn't what it is intended for. It's intended as a LEO taxi. There are a couple of paper studies to turn it into something else, but those will need quite some engineering and of course, a customer, which doesn't exist yet.

What unprofitable reasons ? Even if you bring the price of the seat down to $10 million, which isn't realistic any time soon, it still won't spring new demand. There is still no destination in LEO and a cheap Dragon would still be a bridge to nowhere.

Space flight is an extremely inelastic market.

They could just put their servers on an abandoned oil platform in international waters. It would offer the same safe haven for a fraction of the price. Ever heard of Radio Caroline ?

No it wouldn't. It would be cheaper to just launch a new spacecraft with new servers on it than to launch a manned mission.

An offshore oil rig costs a lot less than that. Or have a chat with the Prince of Sealand.

If you can get HSF prices cheap enough, it would allow enough people to get to space to allow for Space tourism, or possibly a space movie studio, with a small space station, or a refurbrished ISS (assuming anybody picks that offer up).

[Nibb31]

Yeah, yeah. Companies have come and gone on that business model for decades, along with asteroid mining, miracle space drugs, orbital solar stations, and zero-g semiconductors... I'm not holding my breath.

Edited March 17, 2016 by Nibb31