Virgin Galactic

[Aer'ki]

10% decrease in fuel consumption would give you the same 10% in payload increase. That includes the orbital stage weight, though. Not just cargo.

I don't see where you are getting 30% from.

No, no, no...that ratio doesn't fit. The weight of the fuel expended for those 20 seconds of vertical lift is 4 times the weight of the payload. 81% of the shuttle's weight is fuel...shifting 1% of that weight from fuel to payload would give you the 30% increase in payload. By not using vertical launch from ground you should be able to save at least 1% of fuel weight and shift it to payload weight. 30% is the number I'm willing to quote without fear of being wrong. I estimate it to be a great deal higher.

That's called hand-waving. How do you get 200%. Show me the numbers that say 200% or something in the ballpark at least. How much drag? How big is the impact of initial velocity? How much does higher initial velocity increase drag? Give me numbers.

How much drag depends on shape of craft...which we don't have.
Higher altitude launch decrease drag and allows for a higher rate of acceleration.
High end velocity could be as much as 5% of total orbital speed if high altitude lift craft is constructed.
Wings on craft will also reduce fuel consumption.

All of these things both decrease the amount of fuel necessary...but then less fuel means less weight...which then again means less fuel needed, which is again less weight. It snowballs a bit.

I'm pretty sure that you could get 100% increase in payload just from abandoning a vertical ground launch. Throw in all the other factors and I'm fairly confident in the 200% number. As I said, it's ball park, and without an actual craft to begin running numbers on that's the best that can be done.

Maybe you just don't understand what estimate means. It's not a number you make up. It is a number you get from computations using a rough model.

I'm not making up numbers...I'm pinning them down to a range and plucking one from that range that I'd risk a wager on, if that helps explain it better.

Your "rocket fuel" comment won't fly. Shuttle doesn't use expensive fuels, except for the boosters. It's using LOX/LH2, which is pretty cheap. It is comparable in cost to Jet A, which is what your lifter is using, and if fuel cell tech takes off, it will be cheaper than Jet A. Proposed SSTO craft don't use boosters. So it's just the cost of LH2.

A lot of the lift will come from the wings. As for the fuel, it could be anything...even electricty from your fuel cell tech. Also, it would have two sets of engines if its high altitude...some sort of aerospike for the thinner air above which a normal lift craft could carry it.

And what do you mean you can't estimate the fuel consumption? You can work out all that stuff for a rocket, but you can't figure out how much Jet A the lifter is going to take up? How about I help you with some base figures?

Take glide ratio to be about 5.
Take efficiency of jet engines to be about 50%. That's pretty generous for the task.
Take thrust/weight to be about 1/2. (That's thrust = half the weight of the lifter).
Take lifter weight to be about equal to orbiter weight.
Look up the energy/weight of Jet A. (Use figures for Kerosene if you can't find Jet A).

Use what you know about glide ratio to figure out how long it will take to climb to 10 miles and then how much fuel would be consumed.

Maybe after running these, you'll have some idea why the proposal for a Shuttle to be launched from a modified 747 sans boosters was scrapped. Boosters turned out to be cheaper.

Why would lifter weight be equal to orbiter weight? I'd assume it would be much more.

As for cost...don't forget the recover proceedure for the boosters. A lifter will just fly back and land on the same air strip it left from and can be refueled and take off again within the day. How long does it take to refit boosters? There's more to cost of operation than simple fuel prices.

Also, the cost of fuel to weight of payload increases exponentially the larger the payload you use. There is a limit when the rocket just gets too big to launch. Because of this, air launch will always yield larger payloads than vertical ground launch.

Again, you can't do calculations for a craft that doesn't exist. But you can do a basic logical comparison.

Rocket = lift through 100% thrust.
Air launch = lift through thrust + wings.

Based on this simple principle, winged craft will always require less fuel than rockets...type of fuel and current cost are another matter.

[K^2]

No, no, no...that ratio doesn't fit. The weight of the fuel expended for those 20 seconds of vertical lift is 4 times the weight of the payload. 81% of the shuttle's weight is fuel...shifting 1% of that weight from fuel to payload would give you the 30% increase in payload. By not using vertical launch from ground you should be able to save at least 1% of fuel weight and shift it to payload weight. 30% is the number I'm willing to quote without fear of being wrong. I estimate it to be a great deal higher.

Rocket formula. Learn it. Understand it. Work with it.

How much drag depends on shape of craft...which we don't have.

You're estimating. Your form coefficient will be in 0.5-1.0 range. Chop, chop. Get on with it.

Higher altitude launch decrease drag and allows for a higher rate of acceleration.

How much higher. Stop saying words, and start crunching numbers.

High end velocity could be as much as 5% of total orbital speed if high altitude lift craft is constructed.

Good, numbers. It could be, yes, but you'll be flying supersonic (speed of sound is lower at altitude) I was using 200m/s, which is more like 2.5% and stays within sound barrier. But again, either one works for an estimate. So how much fuel does reducing final speed by 5% save you? Do the math.

Wings on craft will also reduce fuel consumption.

Wait, you were just arguing that Shuttle is limited because it has to maintain certain velocity so as not to fall apart. Shuttle's wings is why that happens. You can't have your cake and eat it. Wings are there purely for the landing. You start using them on liftoff, and you cause yourself more trouble than it is worth. Just ignore the wings on the top stage.

All of these things both decrease the amount of fuel necessary...but then less fuel means less weight...which then again means less fuel needed, which is again less weight. It snowballs a bit.

Rocket formula accounts for all that. We don't need to guess about snowball effect here.

I'm pretty sure that you could get 100% increase in payload just from abandoning a vertical ground launch. Throw in all the other factors and I'm fairly confident in the 200% number. As I said, it's ball park, and without an actual craft to begin running numbers on that's the best that can be done.

Hand-waving.

I'm not making up numbers...I'm pinning them down to a range and plucking one from that range that I'd risk a wager on, if that helps explain it better.

More hand-waving.

A lot of the lift will come from the wings. As for the fuel, it could be anything...even electricty from your fuel cell tech. Also, it would have two sets of engines if its high altitude...some sort of aerospike for the thinner air above which a normal lift craft could carry it.

Lift isn't free. It comes with drag. By generating lift, you also subject yourself to a slow, gradual liftoff, which means drag is effecting you over much longer time. Lift does NOT help you save energy on getting up to an altitude. Never has. Never will.

Why would lifter weight be equal to orbiter weight? I'd assume it would be much more.

Dude, I'm giving you a break here. Heavier lifter means more fuel. Lets pretend that we can make a lifter that's very, very light. It still won't let you save on fuel costs, and that's the whole point.

As for cost...don't forget the recover proceedure for the boosters.

SSTO doesn't use boosters. It's a fuel-and-go design. And as I said, fuel is simply LH2 + LOX oxidizer.

Also, the cost of fuel to weight of payload increases exponentially the larger the payload you use.

Rocket formula. No need to guess.

There is a limit when the rocket just gets too big to launch. Because of this, air launch will always yield larger payloads than vertical ground launch.

That's true, which is why at the very beginning I suggested that it would be a very good idea to make air launch possible. And that is planned as an option for the SSTO craft. IF you need to take something really heavy up, you have air lift as an option. If you don't, you save a whole bunch of money with ground launch.

Again, you can't do calculations for a craft that doesn't exist. But you can do a basic logical comparison.

You can look up Lockheed Martin X-33's specs and use them for an estimate, as that is one of the most reasonable SSTO designs. Other SSTO craft would be similar. Any air-lifted craft would also need to be very similar in design.

Rocket = lift through 100% thrust.
Air launch = lift through thrust + wings.

Again, lift isn't free. Correct 'formula':

Rocket = ascent via thrust vertically.
Air launch = ascent via lift + drag + longer trajectory.

Vertical launch will end up cheaper any day of the week. That's why they do it that way.

[RubberJesus]

As for NASA being idiots...I'm not refering to any one person, but the overall design elements that they're using are not functionally wise. Their going back to using capsules because of the nostalgic element is a telltale sign they don't know what they're doing.

the reason they went back to the capsule is to save money, with the space shuttle it's all or nothing, you have to lift the whole ship into orbit just for 6 astronauts, a capsule is MUCH lighter, more weight equals exponentially more fuel, by designing separate rockets for large cargo and for human passengers they actually save a lot of money, performance wise there is nothing the shuttle can do that the capsules and cargo rockets can't do, except land on a runway. the shuttle looks advanced but is actually a money drain waiting to become a safety hazard.

[K^2]

That is absolutely ridiculous. Capsules are non-reusable. They require multi-stage launch vehicles that result in just as much fuel being used per kg of cargo. And they tend to rely on more expensive and less environmentally friendly fuels.

Shuttle was designed with a specific goal in mind. To make space flights routine and affordable. With proper funding, it achieves this goal quite nicely. Problem is, funding was cut. Shuttle is not the most affordable way of running the space program if you only use it to take crew up and from the ISS. But simply maintaining ISS is complete lack of progress. And going back to capsules is a huge step back.

SSTO or even air-lifted single reusable space vehicles would allow to maintain routine flights to orbit at lower budget. Even that is a step back from Shuttle program, but it would be a reasonable compromise for now. At least, it would allow space program to be gradually expanded. Going back to capsules is almost as bad as abandoning the space program all together.

[Aer'ki]

That is absolutely ridiculous. Capsules are non-reusable. They require multi-stage launch vehicles that result in just as much fuel being used per kg of cargo. And they tend to rely on more expensive and less environmentally friendly fuels.

Shuttle was designed with a specific goal in mind. To make space flights routine and affordable. With proper funding, it achieves this goal quite nicely. Problem is, funding was cut. Shuttle is not the most affordable way of running the space program if you only use it to take crew up and from the ISS. But simply maintaining ISS is complete lack of progress. And going back to capsules is a huge step back.

SSTO or even air-lifted single reusable space vehicles would allow to maintain routine flights to orbit at lower budget. Even that is a step back from Shuttle program, but it would be a reasonable compromise for now. At least, it would allow space program to be gradually expanded. Going back to capsules is almost as bad as abandoning the space program all together.

Here we agree, though it is possible to make a reuseable capsule, I imagine.

It is a step backward, and by this I presume NASA doesn't really have a clue how to proceed. Proper procedure to reach the moon would be by establishing INFRASTRUCTURE.

7 piece system to reach Luna:

1. Spaceport on Earth...check.
2. Dropship designed just to go to orbit...check.
3. Starport in LEO...sorta check. Not a very good one, IMO.
4. Starship used as ferry between starports.
5. Starport in Lunar orbit.
6. Dropship for Luna only.
7. Lunar spaceport on surface.

Once established, this will be the most useful and efficent means of travel. The starship components need only be brought up the gravity well once, after which they just float in space and never land. Mission specific pieces allow for speciality in design rather than all-in-one craft that are less efficient and cumbersome.

[K^2]

I don't think US Govt has any serious ambitions for the Moon. It was just election-time talk. NASA would very much like that, but they realize that their funding is going to be bad. And it is US Congress that actually cut funding for both Shuttle and Shuttle-like replacement programs. They are the ones who chose to give money to archaic capsule design. NASA heads were strongly against it. So I wouldn't use it as an argument for idiots in NASA so much as idiots in government.

And yes, that would be the best way to establish a proper base on Luna. Though, for a really successful one, we also need means of producing fuel on Lunar surface. If they find a good source of ice there, they can produce LH2/LOX fuel provided a good solar array is built, which is definitely within the realm of possible right now.

[kymeric]

If only he knew the right people to bribe off in the military to get that super advanced alien technology XD

WTB [NID]

[Aer'ki]

I don't think US Govt has any serious ambitions for the Moon. It was just election-time talk. NASA would very much like that, but they realize that their funding is going to be bad. And it is US Congress that actually cut funding for both Shuttle and Shuttle-like replacement programs. They are the ones who chose to give money to archaic capsule design. NASA heads were strongly against it. So I wouldn't use it as an argument for idiots in NASA so much as idiots in government.

And yes, that would be the best way to establish a proper base on Luna. Though, for a really successful one, we also need means of producing fuel on Lunar surface. If they find a good source of ice there, they can produce LH2/LOX fuel provided a good solar array is built, which is definitely within the realm of possible right now.

All true, but the capsule design had to originate within NASA, whether it came from the heads or not.

[K^2]

All true, but the capsule design had to originate within NASA, whether it came from the heads or not.

Yup, but that's politics, not science. A few prominent research groups within NASA pick up funding to develop a Shuttle-like SSTO or air lifted design. Heads of some other research groups know they can't compete with groups that already got funding, and they try to get some money buy promising to develop a modern capsule alternative for whatever list of reasons they came up with. Then, when congress is looking to cut funding for NASA, these guys see an opportunity. If they act fast, they can convince some senators and reps to reduce total funding by switching all funding to capsule design, they can be receiving the lion's share of funding, and Shuttle guys would be picking up scraps.

[Aer'ki]

Yup, but that's politics, not science. A few prominent research groups within NASA pick up funding to develop a Shuttle-like SSTO or air lifted design. Heads of some other research groups know they can't compete with groups that already got funding, and they try to get some money buy promising to develop a modern capsule alternative for whatever list of reasons they came up with. Then, when congress is looking to cut funding for NASA, these guys see an opportunity. If they act fast, they can convince some senators and reps to reduce total funding by switching all funding to capsule design, they can be receiving the lion's share of funding, and Shuttle guys would be picking up scraps.

Which is why the first base on the moon will probably come from either China or private enterprise.

[K^2]

Which is why the first base on the moon will probably come from either China or private enterprise.

Yup.

[knowles2]

Obviously it will be somewhat safe, all im saying is there is a chance of something going wrong more so here than for example an airplane.


Have you seen the concept art of the spaceport? looks amazing.

It will be somewhat safer than the first aeroplanes an the first trips across the atlantic.
In other words a few crashes in the first decade or two of operations, should be more or less expected an plan for by the company.

Originally Posted by Rodney Mal Doran

The real problem with NASA , in my opinion, is that they are asked to do things but not given the budget to accomplish them. Most of the above are technologically feasible but cost more than NASA has.

No the real problem for NASA is that they are control by politicans who tend disappear very quickly on Nasa time scales which are often 10- 20 years, an are replace by other politicans.
Also Nasa also have to contend with the fact that they only get money for projects which congress approves an generally they only approves projects which bring money to there own states. An that why Nasa project cost ten times more than non government projects, also why they show no interest in replacing there non reusable with reusable space ships, as this would eventually mean massive job losses an no politicians would ever sign such a thing off or allow funding for it. Also the US military tends to take the most promising projects an remove them into there own control an classified the whole thing or slow down Nasa progress on such projects until they run out of money an then take the project in house.

Originally Posted by escyos
space travel!!!

more like upper atmosphere travel for 500 million dollars. such a waste, in 10 years time they will have something better for half the price!

Problem is you need to have a starting point. Most space tech is currently control by the US government, or by other governments around the world. Which means private companies have to developed there own tech which they control. For them to do it they have to attract private investors. An they usually want quick returns on that investment. What virgin Galactic have effectively done is to identified the quickest an cheapest way to develop a craft to LEO but may be not the best way, in the hope they can make money which they can use to attract further investments needed to developed technologies for space craft capable of reaching Earth Orbit. Then once there they can then ask investors or indeed the company may of obtain a big enough capital base to enable them on there own to invest in a earth to moon vehicle an even Earth to Mars an earth to the Asteroids vehicles on it own. I suspect that they will focus on a vehicle capable of being upgraded to be able to achieve all three locations safely. Probably a highly modularise design.

[K^2]

konwles, try not to make multiple posts just to quote several people. You can either edit and insert quote tags yourself, or you can use multi-quote button () to add multiple quotes to the post you are writing.

It might not seem like a big deal to you, but it causes clutter, makes it more difficult to reply to you, and is considered bad tone overall.

[Aer'ki]

It will be somewhat safer than the first aeroplanes an the first trips across the atlantic.
In other words a few crashes in the first decade or two of operations, should be more or less expected an plan for by the company.

Originally Posted by Rodney Mal Doran



No the real problem for NASA is that they are control by politicans who tend disappear very quickly on Nasa time scales which are often 10- 20 years, an are replace by other politicans.
Also Nasa also have to contend with the fact that they only get money for projects which congress approves an generally they only approves projects which bring money to there own states. An that why Nasa project cost ten times more than non government projects, also why they show no interest in replacing there non reusable with reusable space ships, as this would eventually mean massive job losses an no politicians would ever sign such a thing off or allow funding for it. Also the US military tends to take the most promising projects an remove them into there own control an classified the whole thing or slow down Nasa progress on such projects until they run out of money an then take the project in house.


Problem is you need to have a starting point. Most space tech is currently control by the US government, or by other governments around the world. Which means private companies have to developed there own tech which they control. For them to do it they have to attract private investors. An they usually want quick returns on that investment. What virgin Galactic have effectively done is to identified the quickest an cheapest way to develop a craft to LEO but may be not the best way, in the hope they can make money which they can use to attract further investments needed to developed technologies for space craft capable of reaching Earth Orbit. Then once there they can then ask investors or indeed the company may of obtain a big enough capital base to enable them on there own to invest in a earth to moon vehicle an even Earth to Mars an earth to the Asteroids vehicles on it own. I suspect that they will focus on a vehicle capable of being upgraded to be able to achieve all three locations safely. Probably a highly modularise design.

I largely agree, except with this last part. This isn't very efficient. INFRASTRUCTURE is the way to go.

This means a dedicated dropship(lifting/landing craft to Leo) which can be improved on over time, getting larger, cheaper, hardier, and more of them.

A starport in orbit for the dropship to connect to and transfer cargo/personnel.

Then, a starship to transit through space to other starports...say, one for the moon, one for mars, one for Venus, etc. A starship just from Earth to Moon wouldn't have to be very complicated, but one capable of traveling to other planets would need to be larger and more complex.

The key is producing dedicated craft for dedicated missions and not trying to make a 'do it all' craft. Splitting up the workload is the most efficient system. Creating a dropship to Leo is the first step, and Virgin Galactic seems to be on their way there.

[K^2]

Completely agree with Aer'ki on this one. And it's not just the efficiency of it. You also have to keep in mind that we need people up there, in space, who aren't astronauts trained to deal with microgravity for extended periods of time. We need ordinary people, some of whom start to feeling motion seek in a car.

The spaceport-to-spaceport ship may spend days or even months in voyage. It must provide artificial gravity. The only way we know how is with centrifugal effect. A ship with centrifugal gravity is not going to be the kind of thing that will enter atmosphere, and wouldn't be easy to land on a planet/moon devoid of it either.

Landers, in contrast, spend little time not docked to rotating station or not on the surface. And even most of the flight time they undergo acceleration. In fact, by timing the launches right, it is possible to achieve almost perfect 1g gravity from the moment passenger steps onto the lander to the moment that same passenger steps out into the docking area of the spaceport.