Commercial HLV and R&D

[Serafeim]

Jets like the 747 usually have a mass ratio of 2:1

still far enough than space launchers.

in order to have a space faring humankind like the Sci-fi movies etc we will need very compact energy,reactors etc. only this way also we can have maybe lower g launches than chemical rockets,is like comparing Cannon(like that in Vern book) with chemical rockets.

The next step is electric propulsion with reactors.With a compact power like that we can go to orbit with the same acceleration  like a Plane today..So  every bod will can go to space..
in wikipedia says that to launch a electric rocket from ground a power og some GWatts is needed.so maybe near  the next century..

The indermediate solution for me(except chemical rockets of course) is the space elevator..

nasa is giving money for this plan ,but they believe but they believe that is only for the next century..

Like in sci-fi movies,novels etc..

[Robotbeat]

Propellant costs will probably still be enough to keep you and me out of orbit though. Unless fusion reactors become a reality in our lifetime and reduce energy costs dramatically as they might.

Well, the middle class will still not be able to go on an annual vacation to orbit, but a vacation to the Americas was not realistic for the middle class European family in the late 1600s, either, but colonization was proceeding in full force. It will be advances in ISRU (like mining, etc) and other areas that will enable colonization after getting to orbit gets down to $100/kg. At that price point, you'd be able to sell your house and afford to go into space.

I agree that reducing the cost of energy is an important goal that would increase the standard of living for everyone.

[mmeijeri]

I agree that reducing the cost of energy is an important goal that would increase the standard of living for everyone.

Sure, but I was thinking specifically in terms of reducing the cost of propellant. With infinitely cheap power you could afford to make methane or higher hydrocarbons out of atmospheric CO2 and end up being cheaper than fossil hydrocarbons today. We're still a long way away from that of course.

EDIT: not to mention LOX/LH2 from water of course!

[docmordrid]

what is that?is an electric propulsion?
sorry but I dont know it..

A superconducting generator, powered by a small reactor (coolant drives the generator shaft via a turbine) or an alt-fuel turbo-generator, would run electric motors that would replace the jet portions of a turbofan. 

Alternatives also include fuel cell/battery power, which would be only  good only for short flights but perhaps viable for a super-WK2 type launcher.

Think of such a craft, very possibly a UAV to increase efficiency, as the first stage of a launcher akin to what Boeing proposed a long time ago. 

Next Big Future article....

Also: http://wstiac.alionscience.com/pdf/AQV4N1_ART06.pdf  (on small superconducting generators)

[clb22]

Bigelow got tired of State Department b.s. and red tape that went along with using Russian rockets. That's why he would prefer to use American launchers.

Bigelow doesn't have to make any decision on the launch vehicle of any new test (or operational) module yet. The next launch is NET 2015 at the moment. Of course, his company has looked into US launch vehicles as from a paper work perspective, cultural viewpoint and transportation and logistics viewpoint these are the easiest choices. But at the end all will boil down to costs and reliability. Dnepr was chosen over a US launch vehicle (e.g. Taurus) for Genesis I and II because of costs and costs only.

[docmordrid]

And Bigelow learned from it that costs alone are not the entire story.  Cost doesn't mean much if the Feds get into an ITAR snit like they did with Genesis I and II.

[mlorrey]

Propellant costs will probably still be enough to keep you and me out of orbit though. Unless fusion reactors become a reality in our lifetime and reduce energy costs dramatically as they might.

Not quite. The propellant requirements of putting a person in orbit is in the range of sending them from NYC to Sydney, Australia. If you acheive the ability to put someone in orbit for a few multiples of the fuel costs, you have cracked the problem and are destined to be a trillionaire...

In 1492, there was less than a dozen individuals capable of funding a voyage of exploration (i.e. tourism) half way around the world. Within 50 years there were thousands in the new world. In 1620, the Mayflower landed with 102 passengers, half of whome died that winter. Within 50 years there was not only thousands of inhabitants in Boston, but Harvard University had been founded within 16 years of first landing...

[mmeijeri]

Not quite. The propellant requirements of putting a person in orbit is in the range of sending them from NYC to Sydney, Australia.

Assuming you use air-breathing propulsion, right?

If you acheive the ability to put someone in orbit for a few multiples of the fuel costs, you have cracked the problem and are destined to be a trillionaire...

True, but the two statements are not logically incompatible.

[rklaehn]

Jets like the 747 usually have a mass ratio of 2:1

still far enough than space launchers.

But achieving a high propellant mass fraction in a launch vehicle that is basically a tank with an engine at the bottom is much easier than with an airplane with long wings that has to take very large loads in many different directions.

And the 747 is not the state of the art for propellant mass fraction. The rutan global flyer had a dry weight of 1678 kg and a gross weight of 10024 kg, giving a propellant mass fraction of almost 6.

A propellant mass fraction of 20 or more for a rocket stage is not unreasonable, and was historically achieved by several stages. Combine such a stage with a TAN engine, and you have a credible medium-term path to an SSTO vehicle.

[rklaehn]

Not quite. The propellant requirements of putting a person in orbit is in the range of sending them from NYC to Sydney, Australia.

Assuming you use air-breathing propulsion, right?

with an on-site large Lox plant like you would have for a high flight rate spaceport, lox is extremely cheap. Much cheaper than even jet-grade kerosene.

[mmeijeri]

with an on-site large Lox plant like you would have for a high flight rate spaceport, lox is extremely cheap. Much cheaper than even jet-grade kerosene.

Good point, I was thinking of the fuel only, but the oxidiser is of course a much larger fraction of the total propellant mass.

[kevin-rf]

And the 747 is not the state of the art for propellant mass fraction. The rutan global flyer had a dry weight of 1678 kg and a gross weight of 10024 kg, giving a propellant mass fraction of almost 6.

That may be true, but the Global Flyer fly was not designed for the number of cycles a typical 747 experiences over it's lifetime.

To achieve 747 prices for LEO not only do you need a RLV, but you need a robust RLV that can do a large number of cycles. Nothing in LEO/HEO pipe right now (metal, napkin, or powerpoint) is designed to do that.

[rklaehn]

And the 747 is not the state of the art for propellant mass fraction. The rutan global flyer had a dry weight of 1678 kg and a gross weight of 10024 kg, giving a propellant mass fraction of almost 6.

That may be true, but the Global Flyer fly was not designed for the number of cycles a typical 747 experiences over it's lifetime.

Agreed. But the main reason that modern airliners have a propellant mass fraction of around 2 is that they don't need more to fly the longest commercial routes without refueling.

I think a LOX/Hydrocarbon tank with a propellant mass fraction of much more than 20 is well within the state of the art even when designing for a reasonably large number of cycles. The problem is to get an altitude-compensating, throttleable engine with an initial T/W of significantly more than 100/1. TAN takes care of all of this.

To achieve 747 prices for LEO not only do you need a RLV, but you need a robust RLV that can do a large number of cycles. Nothing in LEO/HEO pipe right now (metal, napkin, or powerpoint) is designed to do that.

It does not make sense to shoot for 747 levels of reliability and cycle count with the first attempt. The first RLV will probably be reused 100 times and have an operating cost of an order of magnitude more than propellant costs.

But I don't see anything physically impossible with RLVs with 747 level reliability and costs in the long term.

[Ben the Space Brit]

Skylon has attracted a lot of attention recently for being an air-breathing SSTO.  However, I'd like to raise the issue of an air-breathing TSTO.  More specifically, an extremely heavy-lift cargo 'plane (in the C-5 or An-225 size bracket) whose only function is to take a rocket upper stage and payload up to very high altitude where it is released and ascends to orbit.

The basic concept is well-known and is used in the Virgin Galactic sub-orbital passenger craft.  Virgin also believes that the carrier 'plane can be used for uncrewed orbital cargo launches.  Could this be an answer for Commercial HLV? Instead of investing billions on a gigantic first stage to get the payload off the ground, use an aircraft with much better mass fraction and reusability to do most of the work!

What is the best payload-to-LEO that could be achieved with current technology? In terms of what is possible, I'm thinking of something in the 5m-diameter range with an RL-10/-60 powered upper stage and a high-thrust multi-engine hybrid-fuel lower stage.  The payload would be released at airliner cruising altitude (~35,000ft) and the hybrid stage would be used to get the vehicle supersonic and above 60,000ft before the hydrolox engine cuts in.


[edit]

1) How could I forget Pegasus? Air-breathing TSTO is an operational technology! What we need to know is how easy it is to scale up.

2) IMHO, Ultimately air-breathing TSTO is the quickest practical route to RLV.  You have a large carrier 'plane and either a crew vehicle or a remote/computer-controlled cargo hauler with the same basic configuration so that both are launchable from the same aircraft.  After completing their mission, they re-enter for a horizontal landing before recycling for the next mission.  This archetecture lends itself to reduced costs and high flight rates due to the ease of launch operations compared to VL ELVs.  Specialising the two elements (the carrier 'plane and the OV) means you minimise the amount of redundant technology that you have to carry to orbit or even beyond.

Okay, it is a bit blue sky but, hey! What's the point of a 10-year gap if you aren't going to bother to do something dramatic with it?

[Robotbeat]

rklaehn, I couldn't agree with you more!

Ben the Space Brit: I agree airlaunching can take care of lots of the design problems with trying to get a SSTO rocket engine to work (i.e. high thrust/weight, somehow has to function efficiently at both sea level and vacuum, fighting gravity and atmospheric drag at the same time, while still needing to do all of the work to get to orbit) while bringing some of its own problems (different load paths if you put wings on it like the Pegasus, unable to scale up too much, etc.).

I think it could really work. If you somehow had a carrier plane that could go Mach 2 and to 65,000 feet, a SSTO would be pretty straightforward, actually. The RLV part though, with the difficulty of reentry and landing/recovery, would remain a problem. Some ARMOR TPS and a high-efficiency hydrolox engine with maybe a parasail (or something more efficient) might make this possible.

I think for passenger use, (regular) TSTO makes a lot of sense. You have a very high-performing but still suborbital first stage with a beefed-up "OMS" (burning high efficiency fuels, either hydrolox or methane/lox or high-efficiency kerolox or something) functioning as the upper stage. The upper stage would be part of your LEO spacecraft. The first stage could be a high-performance flyback booster. There's a lot of sense in integrating the upper stage with the spacecraft, since the upper stage has to basically enter orbit, anyways.

A SSTO craft that delivers a crewed spacecraft as a separating payload kind of gets rid of the advantages of having a SSTO. Might as well make it a TSTO craft, with the upper stage integrated into the spacecraft (kind of like the Shuttle, but without a significant non-human payload).


BTW, back on topic, I think a commercial RLV will need to become a commercial RLV HLV if we're going to see anything like 747 economies of scale come in to play, but that's probably 50 years down the road. Time to start work to try to make the equivalent of a Douglas DC-3, not a 747. (Okay, fine, we still have a ways to reach DC-3, first we have to somehow overcome the inertia of having a huge workforce behind only a handful of astronauts and annual flights... A big workforce is fine, but it needs to enable far more astronauts. I guess that means we can't have as good plans and training, but otherwise working in space will remain ridiculously expensive for the next century... or forever.)

[Verio Fryar]

1) How could I forget Pegasus? Air-breathing TSTO is an operational technology! What we need to know is how easy it is to scale up.

Of course, Pegasus is NOT a two stage to orbit. Pegasus has three solid stages plus the carrier aircraft.

[kevin-rf]

X-34...

[A_M_Swallow]

What is the best payload-to-LEO that could be achieved with current technology? In terms of what is possible, I'm thinking of something in the 5m-diameter range with an RL-10/-60 powered upper stage and a high-thrust multi-engine hybrid-fuel lower stage.  The payload would be released at airliner cruising altitude (~35,000ft) and the hybrid stage would be used to get the vehicle supersonic and above 60,000ft before the hydrolox engine cuts in.

To make a first stage able to reach Mach 2 can we still manufacture either of these engines:

a. Concorde's Rolls-Royce Olympus 593-610-14-28?
http://www.janes.com/transport/news/jae/jae000725_1_n.shtml

b. SR71 Blackbird's Pratt & Whitney J58?
http://aerostories.free.fr/technique/J58/J58_01/page10.html

[Jim]

To make a first stage able to reach Mach 2 can we still manufacture either of these engines:

a. Concorde's Rolls-Royce Olympus 593-610-14-28?
http://www.janes.com/transport/news/jae/jae000725_1_n.shtml

b. SR71 Blackbird's Pratt & Whitney J58?
http://aerostories.free.fr/technique/J58/J58_01/page10.html

Those engines are out of production

Pratt & Whitney F119
Pratt & Whitney F100
General Electrical F110
General Electrical F101
 

[Robotbeat]

A B-2 stealth bomber can carry over 18 tons of bombs to a height greater than 50,000 ft and a speed of up to .95 Mach, which is enough weight for a Centaur upper stage and a payload (although not enough volume). Of course we're trying to REDUCE costs, here.