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"SpaceShipTwo could be single stage to SUBorbit."

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exoscientist

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Interesting article here:

SpaceShipTwo could be single stage to suborbit says ESA firm.
By Rob Coppinger
on April 29, 2010 4:24 PM
"Virgin Galactic's SpaceShipTwo could be a single stage to suborbit vehicle using liquid chemical propulsion according to independent research carried out by a company that has been contracted by the European Space Agency for suborbital and hypersonic transport studies."
"... the UK firm came to the conclusion that the volume within which SS2 carries its solid rocket motor and nitrous oxide supply could equally hold a liquid chemical propulsion system capable of providing enough thrust for long enough for a horizontal take-off and ascent to 50,000ft and above without the need for WK2."
http://www.flightglobal.com/blogs/hyper ... gle-s.html

If you also filled up the passenger compartment with fuel leaving only a pilot's cabin could it even become orbital?


Bob Clark
 
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tanstaafl76

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Interesting, but somethings that come to mind:

1) I would think using WK2 would be more efficient

2) Since SS2 is designed to be a glider, I would think it would be safer to launch from 50k feet so if you have any engine issues you can abort and land safely (not necessarily true during take-off when you may not have sufficient altitude to properly bring her back in)

3) I don't think it would necessarily work to fill the whole thing with fuel in an attempt to get to orbit, not only are there probably substantial structural ramifications from the added weight, but it complicates the entire horizontal take-off proposition.
 
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SteveCNC

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While it may work to change out the engine/fuel supply with a liquid fuel system I seriously doubt it will happen . As it is the Hybrid engine is extremely safe compared to any liquid fuel system there is . There are no hazardous materials involved in SS2 as it is now and I suspect the ecological damage is also much lower with a Hybrid engine vs liquid fuel . Do you know how hazardous Hydrazine is and unstable ? Not a substance I would choose to mess with if I have a choice .
 
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aphh

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SteveCNC":32mm8c4w said:
Do you know how hazardous Hydrazine is and unstable ? Not a substance I would choose to mess with if I have a choice .
Hydrazine is actually not used for the main liquid fueled engine propellant, but as monopropellant for attitude and reaction control system. It is currently the choice for nearly all spacecraft and satellite reaction control propellant adding to the huge cost of launching a spacecraft due to it's hazardous nature.

Studies are currently underway to find a safer (and thus cheaper) alternative for Hydrazine. http://www.esa.int/esaMI/Technology/SEMPJQ9KF6G_1.html

I am glad ESA supports studying suborbital spaceflight, and I may have had a small role in that by submitting a proposal to ESA a few years back about case for suborbital spaceflight in science and astronaut training.
 
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SciFi2010

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If that is true than Burt Rutan should definitely design SpaceShipThree or Four as an orbital spacevehicle to make space more affordable for civillians. The big audience will only be interested in space-travel and space-colonization if they can participate in it.
 
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scottb50

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aphh":3616m4ve said:
SteveCNC":3616m4ve said:
Do you know how hazardous Hydrazine is and unstable ? Not a substance I would choose to mess with if I have a choice .
Hydrazine is actually not used for the main liquid fueled engine propellant, but as monopropellant for attitude and reaction control system. It is currently the choice for nearly all spacecraft and satellite reaction control propellant adding to the huge cost of launching a spacecraft due to it's hazardous nature.

Studies are currently underway to find a safer (and thus cheaper) alternative for Hydrazine. http://www.esa.int/esaMI/Technology/SEMPJQ9KF6G_1.html

I am glad ESA supports studying suborbital spaceflight, and I may have had a small role in that by submitting a proposal to ESA a few years back about case for suborbital spaceflight in science and astronaut training.
You could easily have Hydrogen/Oxygen thrusters as long as you have a supply. As far as SS-2 you might have enough room if you eliminate the passengers and crew, but even that would probably not be enough. Then you need the added weight of a heat-shield to get back down. One way containers muight be possible though. Maybe a Centaur type stage with added propellant.
 
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SteveCNC

Guest
I was under the impression that hydrazine is used in main engines as well , however I would be curious exactly what chemicals are used in the engine you propose . I only know how hazardous that substance is because I have had to have parts cleaned in it (we farm that stuff out) and have been told enough to know I don't want anywhere near it .

I guess the biggest reason I defend the hybrid so much is I am the main machinest that worked with spacedev in developing it . There was only a couple safety flaws I saw in development and I'm pretty sure the engine that's in SS2 has had both of them addressed. It's an extremely light system even when fully fueled , 718Inconel main engine but only about .1" thick for most of it and the titainium tanks for the NO2 are about .08" thick . Fuel plug (rubber sort of) only weighs in at roughly 100lbs . I would guess the entire assembly of the engine and fuel tanks and mounts weighs less than 600 lbs fully loaded . I've never looked into the weights of liquid fuel engined but I can't imagine them being anywhere near as light as the hybrid . The only liquid fuel rockets I've worked on were for General Dynamics and later Lockheed Martin the Atlas series II-V but that's a completely different animal .

One limitation a Hybrid has that a liquid fuel dosen't would be how many times you can restart it but I don't think that's too big of a problem for what they plan to do with SS2 right now anyway . Most of the hybrids I worked on could only be started 4 times and IMO the 4th one might be a little iffy depending on several factors . But all in all it's the essence of simplicity right now which I believe gives it the edge over anything else for safety .
 
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aphh

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SteveCNC":299owf0s said:
I was under the impression that hydrazine is used in main engines as well , however I would be curious exactly what chemicals are used in the engine you propose . I only know how hazardous that substance is because I have had to have parts cleaned in it (we farm that stuff out) and have been told enough to know I don't want anywhere near it .
Several proposed suborbital vehicles are planned using kerosene as the main engine fuel. It has lesser energy density (less spesific impulse) than hydrogen when mixed with oxygen/oxidizer, but is easier to handle, safer and already in liquid form without going cryogenic. Then the only cryogenic liquids would be oxygen and/or oxidizer and possibly pressuriser. Cryogenic liquids can be self-pressurising, when they vaporize, energy can be obtained for free which is needed to get enough combustible mixture to flow through the engine which is designed to work without the aid of mechanical turbochargers (turbopumps).

Self-pressurization is also the principle with Hydrazine and other monopropellants. The thrust comes from rapid decomposition of the fuel when heated up, which creates hot gases. The volume is increased dramatically and thrust is created. This is needed in space to turn the spacecraft around, for example.

All this is conventional rocketry, what SpaceX and Falcon-9 is about to use for main propulsion (with turbopumps) and monopropellant for attitude and reaction control.

You make several interesting notes about hybrid motors in your post, and I will have a better look at them.
 
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aphh

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scottb50":3i7y1tuw said:
You could easily have Hydrogen/Oxygen thrusters as long as you have a supply. As far as SS-2 you might have enough room if you eliminate the passengers and crew, but even that would probably not be enough. Then you need the added weight of a heat-shield to get back down. One way containers muight be possible though. Maybe a Centaur type stage with added propellant.
The reason why SS2 needs the first stage to lift it up from the ground is because the hybrid motor is not quite as powerful as liquid fueled engine. Some proposed designs would take off from the runway like a plane using jet engines, which would use the same kerosene fuel as the main rocket engine, that would be ignited at certain altitude.

This was to be the concept for EADS space jet, but as often, cool concept is once again abandoned because of financial constraints:
http://www.flightglobal.com/blogs/hyper ... ce-je.html
 
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scottb50

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aphh":2jiw9uay said:
The reason why SS2 needs the first stage to lift it up from the ground is because the hybrid motor is not quite as powerful as liquid fueled engine. Some proposed designs would take off from the runway like a plane using jet engines, which would use the same kerosene fuel as the main rocket engine, that would be ignited at certain altitude.

This was to be the concept for EADS space jet, but as often, cool concept is once again abandoned because of financial constraints:
http://www.flightglobal.com/blogs/hyper ... ce-je.html
Eventually an orbital container could probably be handled by SS-2, a couple thousand pounds to orbit probably being optimistic.
 
E

exoscientist

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Another interesting article:

Virgin Galactic unveils SpaceShipTwo; Plans open architecture spaceship.
By Larry Dignan | January 23, 2008, 7:42am PST
'“Our vision of White Knight 2 would be part of a much longer development program. Have open architecture like Linux to allow other people to develop new vehicles and revolutionize new industrial uses of space,” said Will Whitehorn, president of Virgin Galactic, Virgin’s spaceline.
"Whitehorn clarified the open architecture point a bit: He said that if interested parties come to Virgin and Scaled Composites they can use key points such as WhiteKnightTwo’s wing to build new aircraft. “We will work with people that come to work with us to do new things with the WhiteKnightTwo. If people come to us we’ll work with them.”
"Whitehorn added that interested parties are already in discussions about building off of the properties of WhiteKnightTwo, but wasn’t going to name names. Overall, Virgin Galactic wasn’t detailing technical details behind the spaceship effort."
http://www.zdnet.com/blog/btl/virgin-ga ... eship/7678

If Virgin Galactic really is serious about this, then I foresee passenger orbital flights proceeding quite apace!

Bob Clark
 
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mr_mark

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Hey everyone, Spaceship 2 cannot become a orbital vehicle without greatly increasing it speed and weight. The very idea that this vehicle in it's current configuration could be orbital is a joke. Reentry cannot be achieved without a heat shield. The aerobraking that spaceship 2 uses would not be effective reentering from orbit. It cannot reenter along an deorbital path. It can only reenter up and down as you do with suborbital flight. Right now Spaceship 2 travels at most 3,500 miles per hour not nearly enough to achieve orbit. With the added heatshield weight there's no way this craft could ever achieve orbit. Also structurally, spaceship 2 can in no way stand up to the orbital speeds and pressures of orbital spaceflight.You guys are dreaming... let's get real and please study a little before making these outlandish assumptions.
 
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bdewoody

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mr_mark":1pthr3iw said:
Hey everyone, Spaceship 2 cannot become a orbital vehicle without greatly increasing it speed and weight. The very idea that this vehicle in it's current configuration could be orbital is a joke. Reentry cannot be achieved without a heat shield. The aerobraking that spaceship 2 uses would not be effective reentering from orbit. It cannot reenter along an deorbital path. It can only reenter up and down as you do with suborbital flight. Right now Spaceship 2 travels at most 3,500 miles per hour not nearly enough to achieve orbit. With the added heatshield weight there's no way this craft could ever achieve orbit. Also structurally, spaceship 2 can in no way stand up to the orbital speeds and pressures of orbital spaceflight.You guys are dreaming... let's get real and please study a little before making these outlandish assumptions.
Yeah there is a lot of difference between the 3-4 thousand mph that SS2 can achieve and the 17,500 mph needed for orbital velocity. Rutan is nowhere near having an orbital passenger space ship.

And I doubt that SS2 will ever be launched from the ground. It's design is linked to it's mother ship.

I also believe there is a future in designing orbital vehicles that are launched from some sort of mother ship that can climb to the 70-80K feet range. The original concept for the space shuttle called for such a design but it was passed over because of the startup cost even though it was agreed that in the long run it would be less expensive.
 
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mr_mark

Guest
That said, I think that Spaceship Two is a fantastic design for what it does and that is suborbital flight. Spaceship 3 is being planned as a point to point suborbital vehicle as announced by Scaled and Virgin Galactic about 4 months ago. The idea is to be able to travel vast areas in very little time by using the suborbital route say California to Japan in 2 hours. By putting more people into suborbital space Scaled and Virgin will be taking a great step forward for passenger travel. If you're looking for a orbital return type vehicle Dreamchaser is your baby and will launch from an Atlas rocket. Expect trials by 2020. Till then there's Spacex's Dragon which I here is nearing completion in California as we speak. Of course that is not a winged vehicle and Spacex is eventually gearing Dragon for deep space operations.
 
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exoscientist

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SteveCNC":1f7dwmmd said:
I was under the impression that hydrazine is used in main engines as well , however I would be curious exactly what chemicals are used in the engine you propose . I only know how hazardous that substance is because I have had to have parts cleaned in it (we farm that stuff out) and have been told enough to know I don't want anywhere near it .
I guess the biggest reason I defend the hybrid so much is I am the main machinest that worked with spacedev in developing it . There was only a couple safety flaws I saw in development and I'm pretty sure the engine that's in SS2 has had both of them addressed. It's an extremely light system even when fully fueled , 718Inconel main engine but only about .1" thick for most of it and the titainium tanks for the NO2 are about .08" thick . Fuel plug (rubber sort of) only weighs in at roughly 100lbs . I would guess the entire assembly of the engine and fuel tanks and mounts weighs less than 600 lbs fully loaded . I've never looked into the weights of liquid fuel engined but I can't imagine them being anywhere near as light as the hybrid . The only liquid fuel rockets I've worked on were for General Dynamics and later Lockheed Martin the Atlas series II-V but that's a completely different animal .
One limitation a Hybrid has that a liquid fuel dosen't would be how many times you can restart it but I don't think that's too big of a problem for what they plan to do with SS2 right now anyway . Most of the hybrids I worked on could only be started 4 times and IMO the 4th one might be a little iffy depending on several factors . But all in all it's the essence of simplicity right now which I believe gives it the edge over anything else for safety .
Thanks for the info. I'm interested in what are the dry weights, i.e., non-fueled, of the SS1 and SS2 motors.
The number you gave of 600 lbs fueled for the SS2 motor seems low to me. Perhaps you meant the SS1 motor, not SS2? Or perhaps this only includes the solid fuel and not the LOX?

Bob Clark


Edit: that LOX should have been NO2, nitrous oxide, as the oxidizer.
 
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exoscientist

Guest
The usefulness of just using a single stage for the suborbital flights is to save on costs. Using two vehicles would cost twice as much to develop and twice as much in per flight costs.
Note that XCOR is the leading suborbital tourism venture after Virgin Galactic. They plan to take off with a single craft from the ground rather than using a two-stage system. The reason they can do this is because they are using a higher performance liquid-fueled engine rather than VG's hybrids. Note, also they will charge $100,000 for the suborbital flight, half of what VG is charging.

Bob Clark

[youtube]http://www.youtube.com/watch?v=3a-l1tb1rPg[/youtube]
 
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exoscientist

Guest
Take a look at the attached diagram to get an idea of the volume you could fill with propellant for SS2.
It's a roughly cylindrical space about 40 feet long. Divide this by 3.28 to get the length in meters, 12.2 meters. You could estimate the diameter also from this diagram but this page gives the fuselage diameter as 2.28 meters:

SpaceShipTwo - Wikipedia, the free encyclopedia.
http://en.wikipedia.org/wiki/SpaceShipTwo

Then the cylindrical volume is PI*(radius^2)*length = (3.1416)*(1.14^2)*12.2 = 49.8 m^3. Take the overall density of kero/LOX propellant as 1030 kg/m^3. Then this amounts to a propellant mass of 51,300 kg.
The fuselage does taper off towards the end so you should get a more accurate estimate by modeling this volume as a conical frustum:

Conical Frustum.
http://mathworld.wolfram.com/ConicalFrustum.html

The question is what is the dry mass of SpaceShipTwo?


Bob Clark

 
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SteveCNC

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exoscientist":3lm8wxf7 said:
Thanks for the info. I'm interested in what are the dry weights, i.e., non-fueled, of the SS1 and SS2 motors.
The number you gave of 600 lbs fueled for the SS2 motor seems low to me. Perhaps you meant the SS1 motor, not SS2? Or perhaps this only includes the solid fuel and not the LOX?

Bob Clark
Yeah the 600lbs was from ss1 , after seeing the motor for ss2 yesterday I would have to say it's roughly double the size of SS1 maybe even a little bit more though the design is still the same as that motor is completely scalable from what Chris at spacedev tells me . I would have to guess 1200-1500lbs fully loaded for the actual ss2 motor but that's still pretty light compared to most and it's thrust/weight ratio is very nice for a lightweight frame such as ss2 . I think Scaled.com still has the flight video up from ss1 .

Edit * the dry weights of the SS1 motor was about 60lbs before mounting it and loading it with the fuel and starters . SS2 I'm not certain but judging by the design of the others I would hazard a guess of about 200lbs with nothing loaded . the frame and mounts were just 2124 aluminum not real heavy and the 4 titainium tanks for SS1 with the rings mounted weighed about 100lbs , I've not seen SS2's NO2 tanks so not certain about them or maybe it's just one tank I don't know .

I just know one thing about the hybrid , you do not want to run out of fuel plug before you turn off the NO2 or it will first burn thru the phenolic liner then it will go thru the Inconel (it happened once during a test fire on engine#2) yikes the hole was pointing straight at one of the NO2 tanks .

I've made a few motors for UC-Berkeley , but they were small , maybe 150lbs loaded supposed to be for a satalite I believe , I've thought about making myself a really small one to play with out at the desert but haven't done it yet . After all the design is in my head , why not ! And it's pretty safe since there's not much chance of explosion or anything .
 
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SteveCNC

Guest
You know the actual cost of a flight from VirginGalactic is actually pretty cheep at least from a fuel point of view , they appear to be wanting to get back the invested money in R&D a bit faster is all . Not sure what the ground support would cost or anything , probably not cheap and I'm sure the pilot want to make a few bucks too so maybe the real cost not counting R&D is 30k a person at most . From what I hear the carbon-fiber design dosen't have fatigue issues like the shuttle or even normal aircraft so I think maintenance is lower for them as well and refuelling a hybrid involves pulling one end off and pulling out the old sleeve/plug and sliding a new one in , put the 120 :roll: rivets that hold the end on back in , fill up the NitrousOxide and your good to go .
 
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aphh

Guest
bdewoody":30kqnnk6 said:
Yeah there is a lot of difference between the 3-4 thousand mph that SS2 can achieve and the 17,500 mph needed for orbital velocity. Rutan is nowhere near having an orbital passenger space ship.
It seems like a big gap, but what is needed is just longer burn time and more fuel to continue to accelerate.

Let's say a light spacecraft like SS2 required 50 seconds to accelerate from near 0 mph to 4000 mph. Then another 50 second boost would gain another 4000 mph of delta-V or velocity change, so twice the amount of fuel and burn time would give you 8000 mph.

By extrapolating we can get a rough figure of 4 times the burn time and fuel would give 16 000 mph of speed all else being equal. A burn time of 3 minutes and 20 seconds to reach near orbital speed is in the ballpark for a second stage of a rocket system, as SS2 would be.

Obviously it will be a tremendous engineering challenge to make the orbital leap.
 
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exoscientist

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SteveCNC":3t2uom08 said:
exoscientist":3t2uom08 said:
Thanks for the info. I'm interested in what are the dry weights, i.e., non-fueled, of the SS1 and SS2 motors.
The number you gave of 600 lbs fueled for the SS2 motor seems low to me. Perhaps you meant the SS1 motor, not SS2? Or perhaps this only includes the solid fuel and not the LOX?

Bob Clark
Yeah the 600lbs was from ss1 , after seeing the motor for ss2 yesterday I would have to say it's roughly double the size of SS1 maybe even a little bit more though the design is still the same as that motor is completely scalable from what Chris at spacedev tells me . I would have to guess 1200-1500lbs fully loaded for the actual ss2 motor but that's still pretty light compared to most and it's thrust/weight ratio is very nice for a lightweight frame such as ss2 . I think Scaled.com still has the flight video up from ss1 .
Edit * the dry weights of the SS1 motor was about 60lbs before mounting it and loading it with the fuel and starters . SS2 I'm not certain but judging by the design of the others I would hazard a guess of about 200lbs with nothing loaded . the frame and mounts were just 2124 aluminum not real heavy and the 4 titainium tanks for SS1 with the rings mounted weighed about 100lbs , I've not seen SS2's NO2 tanks so not certain about them or maybe it's just one tank I don't know .
I just know one thing about the hybrid , you do not want to run out of fuel plug before you turn off the NO2 or it will first burn thru the phenolic liner then it will go thru the Inconel (it happened once during a test fire on engine#2) yikes the hole was pointing straight at one of the NO2 tanks .
I've made a few motors for UC-Berkeley , but they were small , maybe 150lbs loaded supposed to be for a satalite I believe , I've thought about making myself a really small one to play with out at the desert but haven't done it yet . After all the design is in my head , why not ! And it's pretty safe since there's not much chance of explosion or anything .
Thanks for the informative response. But can you comment on this Astronautix page that gives the empty mass of the SS1 motor as 300 kg:

SpaceDev Hybrid.
http://www.astronautix.com/engines/spaybrid.htm

When you are giving the empty weight as 60 lb are you including the mass of the solid fuel tank? For solid rocket motors you need to include the mass of the tank in the engine weight since that is where the combustion takes place. For a hybrid you have to include the weight of the solid fuel tank, but not the oxidizer tank, because again that is where the combustion takes place.


Bob Clark
 
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vattas

Guest
aphh":30oe35ip said:
Let's say a light spacecraft like SS2 required 50 seconds to accelerate from near 0 mph to 4000 mph. Then another 50 second boost would gain another 4000 mph of delta-V or velocity change, so twice the amount of fuel and burn time would give you 8000 mph.
This could be true if you reached 4000mph, refueled and then accelerated further. But it's very unlikely scenario...
You forgot that you accelerate not only empty spacecraft weight, but also fuel that you need to accelerate further. So dependency of required fuel is not linear, it's exponential.
I don't know exact formulas to calculate (too lazy now to look them up) amount of fuel needed.
 
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aphh

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vattas":1pqa9gh6 said:
This could be true if you reached 4000mph, refueled and then accelerated further. But it's very unlikely scenario... You forgot that you accelerate not only empty spacecraft weight, but also fuel that you need to accelerate further. So dependency of required fuel is not linear, it's exponential.
I don't know exact formulas to calculate (too lazy now to look them up) amount of fuel needed.
The engine would have to be four times as powerful to accelerate four times the initial mass at the same rate. But, as the amount of fuel and thus mass goes down, acceleration goes up as per F = m * a tells us. So the acceleration is also not constant.

If the acceleration was the same at the beginning with four times the mass and four times the thrust, it would also be four times greater at the end of the boosted flight profile when the fuel has been nearly exhausted.

I made the estimation using 3.6 G average rate of acceleration, which is suitable for human spaceflight. As has been suggested by some, Rutan actually has the ingredients for a orbital vehicle already. It's just not going to be piloted at first, but will be used to launch small satellites to orbit at first.
 
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SteveCNC

Guest
300kg would have to include everything about the engine , all piping from the tanks, the mounting structure , control valves , you name it and it's included in that weight , the engine by itself is nowhere near that heavy , even with both ends on it I could pick it up by myself no problem (and I'm not a muscle builder) . Wish I could just kick you a drawing but I don't work at that particular shop anymore and I'm sure it was proprietary information anyway . How it worked is no secret but the exact specs I couldn't give them even if I had them .

I quit working for that company a few years ago after they were late on payroll 6 times , turns out one of the owners had a major gambling problem and was killing the company bank account . Where I'm at now we starting doing business with spacedev a few months ago although we haven't built any motors (I wish) , we did make some of the support hardware for something (not sure what it ended up on) but it was a pretty heavy thing made of 4130 chromoly , most likely ground hardware . Parts like that don't normally get into space , massive without reason means not flight hardware .

Truth be told I'm thinking about changing locations , get out of california all together . Maybe go work for Bigelow Aerospace in Vegas ;) it could be interesting .
 
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