SpaceShipTwo Second Powered Flight

[Mr Shifty]

Not exactly a space flight yet, but getting there: 65,000 feet, Mach 1.6

Article with more info:

http://www.space.com/22660-virgin-galactic-spaceshiptwo-rocket-test.html

[dharak1]

Awesome! I like the way its going but i don't think that virgin galactic will be the first to make a globally affordable system.

[NGTOne]

The upshot to VG is that they actually have all the funding they need to see these projects through to completion (something a lot of modern space projects, unfortunately, lack - Branson's really cool that way) - I wouldn't be surprised if SpaceShip3 were a design for an orbital spaceplane of some variety.

[Nibb31]

Awesome! I like the way its going but i don't think that virgin galactic will be the first to make a globally affordable system.

A system for what? It is basically a glorified vomit comet. If all you want is several minutes of weightlessness, it is still cheaper to book a parabolic flight on zero-G aircraft.

The upshot to VG is that they actually have all the funding they need to see these projects through to completion (something a lot of modern space projects, unfortunately, lack - Branson's really cool that way) - I wouldn't be surprised if SpaceShip3 were a design for an orbital spaceplane of some variety.

If Virgin ever wants to offer orbital flights, they would be much better off with an off-the-shelf spacecraft like DreamChaser or Dragon. Air launch is dead end for orbital flights.

[Thaniel]

Well, Vg is currently working on an orbital launcher from their existing WhiteKnight 2 that is intended for launching the Spaceship 2. It´s the LauncherOne ( Is it only me? Or do these names somewhat resemble IKEA furniture naming?) http://www.virgingalactic.com/launcherone But agreed, if they intend to launch humans, or significant cargo into orbit, then upscaling WhiteKnight2 by 10-20-50 times won´t get that much more into orbit.

[Moon Goddess]

I suspect that Vertical Launch simply will not be feasible for tourist flights. Too much training for the G forces involved.

[Kryten]

You'll get pretty much the same peak G-forces from vertical launch as horizontal, the limit is engine technology.

[OdinYggd]

I suspect that Vertical Launch simply will not be feasible for tourist flights. Too much training for the G forces involved.

I've read that if you had enough fuel, you could make the ascent as gently as an old lady working her way up a flight of stairs.

Of course it raises a fuss with your dV and mass ratio, but the limiting factor is one of fuel efficiency and cost effectiveness.

[Nibb31]

Well, Vg is currently working on an orbital launcher from their existing WhiteKnight 2 that is intended for launching the Spaceship 2. It´s the LauncherOne ( Is it only me? Or do these names somewhat resemble IKEA furniture naming?) http://www.virgingalactic.com/launcherone But agreed, if they intend to launch humans, or significant cargo into orbit, then upscaling WhiteKnight2 by 10-20-50 times won´t get that much more into orbit.

LauncherOne is only for launching nanosats or other very small payloads as a way of spreading the maintenance cost of the WK2 over various programs. No way can it be upscaled to launch a human being.

I suspect that Vertical Launch simply will not be feasible for tourist flights. Too much training for the G forces involved.

Not necessarily. G-loads are more a matter of thrust/weight than anything to do with vertical or horizontal launch. A soyuz launch has a max of 4G (although landing and reentry are much tougher). The Shuttle was around 3G for launch and reentry. Some rollercoasters are harsher than that and don't require any special training.

[Thaniel]

LauncherOne is only for launching nanosats or other very small payloads as a way of spreading the maintenance cost of the WK2 over various programs. No way can it be upscaled to launch a human being.

I believe I wrote something awfully similar to that, just with more words, and not mentioning the economic benefit of being able to use the WK2 for two different purposes (something wich should be obvious), in the post you just replied to, XD Hence the notation of not being able to upscale the LauncherOne to 10-20-50 times it´s current capacity, wich would allow for humans into space. The problem would ofcourse be to upscale the WK2 to the same capacity. Wich I don´t see happening any time soon.

[Mr Shifty]

Not necessarily. G-loads are more a matter of thrust/weight than anything to do with vertical or horizontal launch. A soyuz launch has a max of 4G (although landing and reentry are much tougher). The Shuttle was around 3G for launch and reentry. Some rollercoasters are harsher than that and don't require any special training.

The Space Shuttle's max launch G forces were also not during vertical flight (though it really makes no difference -- same axis.) They were during the period of near horizontal flight just prior to MECO. This shouldn't be surprising; the ET was almost empty at that point (higher TWR) and most of the thrust was being used to accelerate rather than resist gravity. G-forces just after launch were about 1.7, which is less than you experience doing a standing jump with your legs.

[Thaniel]

Been digging a bit, found some tinteresting numbers around. Like, the AN 255 can lift as much as 247 tons of cargo. The Titan 2 ICBM used to launch the mercury capsules weight fully fueled some 154 tons, and the gemini capsule with a crew of 2 weight in at just below 4 tons. So, if lifted by aircraft to above the thickest part of the atmosphere, a rocket that could be able to lift something along the lines of a gemini capsue size/weight into LEO should be possible. So designing WK 3 with a capacity of some 150 tons is a reasonable goal. And there is no real reason why a rocket launched horizontaly, with a throttled engine, couldn´t be used to get to LEO.Guaranteed, VG have poked their nose into the idea, or they´d be stupid.

[Mr Shifty]

And there is no real reason why a rocket launched horizontaly, with a throttled engine, couldn´t be used to get to LEO.Guaranteed, VG have poked their nose into the idea, or they´d be stupid.

Pegasus rockets have been launched this way since 1990: http://en.wikipedia.org/wiki/Pegasus_(rocket)

[Kryten]

Branson was looking at SS3 as an orbital spaceplane, but that lasted pretty much until somebody gave him a cost estimate. They're now looking at much vaguer plans for point-to-point suborbital.

[Thaniel]

Pegasus rockets have been launched this way since 1990: http://en.wikipedia.org/wiki/Pegasus_(rocket)

Let me rephrase then: "And there´s no real reason why a MANNED(or womaned) horizontaly launched rocket can´t be launched to LEO." I realy hoped that was the intended payload here. I dug around a bit, and some very rough calculations/guestimates gave me a probable capacity for WK3 would only need to be a bit more than a 100 tons. ( I came to 105.ish) if using hybrid engines atleast for the main booster. Would cost a pretty penny to develope that generation of planes, would be by far the largest hybrid launched from aircraft in history, and quite possibly pose new challenges. Edited September 6, 2013 by Thaniel

[Nibb31]

There are several problems with air-launch.

First you need to custom design and build a liquid-fueled rocket that can be hung horizontally fully fueled under. The structure and payload must be designed to withstand both longitudinal stress (when the engines are burning) and lateral stress (when hanging underneath the carrier aircraft). This means that there will be a weight penalty.

Second, there are a whole lot of LOM abort modes if something goes wrong with the launcher or the aircraft:

- If the engine fails to start after being dropped, you lose the launcher instead of it just standing on the pad until you fix it.

- If you abort the launch before dropping the rocket, you need to land with a fully fueled bomb under your belly and pray that the landing gear works.

Finally, the actual gain is rather small. Sure, you will save a small amount of delta-v by launching from altitude, but you are still going to need an expendable multi-stage launcher that can accelerate to 24000 km/h. The cost of building and maintaining a specially designed aircraft for this single task instead of just making your first stage slightly bigger, as well as all the added complexity, is not necessarily worth it.

It is feasible for small rockets, such as Pegasus (also the cost-effectiveness of Pegasus was dubious), but it doesn't scale well.

Edited September 6, 2013 by Nibb31

[Thaniel]

There are several problems with air-launch.First you need to custom design and build a liquid-fueled rocket that can be hung horizontally fully fueled under. The structure and payload must be designed to withstand both longitudinal stress (when the engines are burning) and lateral stress (when hanging underneath the carrier aircraft). This means that there will be a weight penalty.

*sigh* those aren´t problems per se, those are "design requirements",needing a process often called "engineering", wich are what usualy goes on when designing a purpose built craft of most any kind. No surprise there. As for examples that it has been done before, there is a company called Virgin Galactic who have proven that it is possible to build purpose built crafts that can both fly, carry other vehicles, drop said vehicles in mid-air, and those vehicles are able to handle both the stress of being carried under a wing, and being propeled by a rocket engine. Using hybrid rocket tech btw. solid/liquid fuel. Wich when stored, is not considered an explosive compared to solids, and much more stable and predictable than pure liquid setups. Using liquid oxidizer for such horizontaly launched vehicles is known to work just fine btw.

Second, there are a whole lot of LOM abort modes if something goes wrong with the launcher or the aircraft:- If the engine fails to start after being dropped, you lose the launcher instead of it just standing on the pad until you fix it.- If you abort the launch before dropping the rocket, you need to land with a fully fueled bomb under your belly and pray that the landing gear works.

Well, if using any form of liquid fuel, that is not poisonous, or even just an oxidizer, it is possible to dump it over board. And by purpose building the carrier plane, it is possible to make it with overdimensioned undercarriage able to handle such a landing just fine. It´s been done before, for decades.

Finally, the actual gain is rather small. Sure, you will save a small amount of delta-v by launching from altitude, but you are still going to need an expendable multi-stage launcher that can accelerate to 24000 km/h. The cost of building and maintaining a specially designed aircraft for this single task instead of just making your first stage slightly bigger, as well as all the added complexity, is not necessarily worth it.

I challange you to cough up atleast some rough estimates of the difference for this. Sure, the benefit is limited, but consider the WK2, if all goes to plan, it will be used for launcing both satelites and people. Building something able to launch to orbit, cheaper than ordinary vertical launced boosters, will have orders queing up. The benefit of being able to launch from different locations, more or less by will, will also be apreciated for the more "exotic" orbits. So no, so far, from what I´ve seen around, the benefits of such a profile, both economic and flexibility wise and safety-wise does seem intriguing.

It is feasible for small rockets, such as Pegasus (also the cost-effectiveness of Pegasus was dubious), but it doesn't scale well.

It all boils down to the engineering compromises they will have to make contra the benefits of using modern materials and knowledge. Give VG a few years of first hand experience, and who knows what new plans they might hatch. Edited September 6, 2013 by Thaniel

[Mr Shifty]

Basically what you get with an air-lift is a crewed first stage, capable of launch from any airfield that can handle the aircraft and full RTLS. WhiteKnightTwo is a pretty pathetic first stage though: about 9 miles of altitude and maybe 200 knots. Compare to the Soyuz solid boosters, which separate at about 28 miles of altitude and 3000 knots. I suppose there's probably a good reason only suborbital crewed flights launch this way.

[Karriz]

Here's another video, it really looks awesome up there:

[Moar Boosters]

Looks scary as hell! Wobbling and oscillating all over the place. I'd be looking to revert back to the hanger, and adding more struts, sas and re-balancing the wings.

[Nibb31]

*sigh* those aren´t problems per se, those are "design requirements",needing a process often called "engineering", wich are what usualy goes on when designing a purpose built craft of most any kind. No surprise there.

Certainly, those engineering problems are not unsolvable, but they still need solving. Orbital rockets are already have very constrained requirements with relatively low margins. Additional requirements will substantially increase the development cost and force you to compromise other parameters of the vehicle. For example, a rocket that is designed to be fueled vertically only needs ribbing or reinforcements on the longitudinal axis. If you have to add lateral reinforcements, with internal struts or plates, it will end up being heavier, which will impact performance. This means that the upper stage will need to be a bit larger to compensate, and the aircraft, which has its own constraints, might need to be even heavier, etc...

Sure, it can be done, but it has a cost. And that cost might not be worth the expense.

As for examples that it has been done before, there is a company called Virgin Galactic who have proven that it is possible to build purpose built crafts that can both fly, carry other vehicles, drop said vehicles in mid-air, and those vehicles are able to handle both the stress of being carried under a wing, and being propeled by a rocket engine.

Actually, Virgin hasn't proven anything. The system is designed and built by Scaled Composites. Virgin is only the operator. And the concept has existed for a long time, ever since NASA dropped the Bell X-1 from a B-29, even if SS2 is actually closer to the X-15.

However, it's a system that simply doesn't scale well. An aircraft is a pretty crappy substitute for a first stage, so you still need a multi-stage rocket, albeit somewhat smaller, but at the cost of a huge one-off aircraft that is going to spend most of its time in a hangar instead of flying. An airplane might be reusable, but it's still way more expensive than a dumb booster or a bit of extra tankage.

Sure, the benefit is limited, but consider the WK2, if all goes to plan, it will be used for launcing both satelites and people.

WK2 might be capable of launching nanosats, a couple of kilograms into orbit. It won't be cheap though, because the rocket is still expendable. As for people, SS2 is a roller coaster ride. It doesn't go to orbit. It doesn't leave the atmosphere. It doesn't even go hypersonic. To do those things would require much more technology, complexity, cost, and weight. It would have to be 10 times bigger and heavier, and the air launch concept simply doesn't scale well for that.

You would get better performance by strapping a couple of cheap SRBs to the side of your rocket.

Building something able to launch to orbit, cheaper than ordinary vertical launced boosters, will have orders queing up.

Why would it be cheaper than, for example, piggybacking a nanosat on a commercial launch? or a Pegasus or Minotaur launch? You still have to pay for a disposable rocket, and the flight time of a unique aircraft, with a huge development cost, such as WK2 is not going to be cheaper than using SRBs as a first stage, or just designing your disposable rocket to be slightly bigger.

The benefit of being able to launch from different locations, more or less by will, will also be apreciated for the more "exotic" orbits. So no, so far, from what I´ve seen around, the benefits of such a profile, both economic and flexibility wise and safety-wise does seem intriguing.It all boils down to the engineering compromises they will have to make contra the benefits of using modern materials and knowledge. Give VG a few years of first hand experience, and who knows what new plans they might hatch.

Yes, there is a launch flexibility benefit. You can launch regardless of the weather and at any time from any location, but how many nanosats are that picky on flexibility? The only folks who might have that sort of requirement are the military, but they aren't too interested in nanosat-class payloads. They already have their own solutions (Pegasus) or ASAT missiles that can be fired from an F-16.

Edited September 6, 2013 by Nibb31

[Nibb31]

Here's another video, it really looks awesome up there:

Wow! That looked really wobbly... and judging from the pilot's voice, they must have been getting some high Gs when the engine kicked in!

[metaphor]

Cool video. There's probably something wrong with the pilot's comm, because he has that same voice during the zero-g phase.

In regards to having an airplane as the first stage, there's a Pegasus II rocket ( http://en.wikipedia.org/wiki/Pegasus_II_(rocket) ) that will be able to carry 6 tons to orbit. That's probably enough for a Gemini-size capsule.

There's also the Skylon SSTO ( http://en.wikipedia.org/wiki/Skylon_(spacecraft) ), but it's not clear whether that will actually happen.

[PakledHostage]

*sigh* those aren´t problems per se, those are "design requirements",needing a process often called "engineering", wich are what usualy goes on when designing a purpose built craft of most any kind.

I don't want to start any arguments, but it would certainly benefit you to back up your claims with some numbers and facts if you start a post with that much snark...

I challange you to cough up atleast some rough estimates of the difference for [launching from altitude vs. launching from the ground].

Challenge accepted (on behalf of Nibb31):

Assumptions

- Delta-V expended by the space shuttle is typical of launch vehicles

- The shuttle's SSMEs produce a constant combined thrust of 1125000 lbf at 100% throttle (ref: http://www.nasa.gov/returntoflight/system/system_SSME.html)

- The shuttle's SSMEs have an ISP of 455 seconds (ref: http://en.wikipedia.org/wiki/Space_Shuttle)

- The SRBs produce a constant combined thrust of 5300000 lbf (ref: http://www.nasa.gov/returntoflight/system/system_SRB.html)

- The SRBs have an ISP of 269 seconds (ref: http://en.wikipedia.org/wiki/Space_Shuttle)

- The launch profile given in the NASA press kit for STS-30 is typical of launch vehicles

Per the launch profile given in the NASA press kit for STS-30, the shuttle reaches 37000 feet altitude in 1 minute, 2 seconds. It is travelling basically straight up at 435 m/sec by that point. (Note: Even 30° off vertical is still 87% straight up...)

Using the values I gave above, I approximated the delta-V expended during 4 phases of flight, from launch to MECO:

0 - 30 seconds, throttle = 104%, Delta-V ≈ 0.47 km/sec

30 - 62 seconds, throttle = 65%, Delta-V ≈ 0.56 km/sec

62 - 125 seconds, throttle = 104%, Delta-V ≈ 1.75 km/sec

125 - 511 seconds, throttle = 104%, Delta-V ≈ 6.79 km/sec

Total delta-V expended to MECO ≈ 9.56 km/sec. Note that this total delta-V is almost certainly low. The SSME's Isp is certainly higher in a vacuum than it is at 1 atm, but I used the values for 1 atm to be conservative. (i.e. a lower overall delta-V to orbit increases the relative benefit of launching from a carrier aircraft.)

Let's assume that a launch vehicle is dropped from a carrier aircraft at 37,000 feet going 235 m/s (Mach 0.8) horizontally. Let's then be generous and assume that the launch vehicle has wings that allow it to redirect all of that speed vertically without any expenditure of delta-V. The weight of those wings will affect payload capacity however. The extra structural weight that will be required for the tank to sustain lateral stresses during climb to launch altitude and during the turn from horizontal to vertical will also affect payload to orbit.

In that case, your rocket will need an additional instantaneous delta-V of 200 m/s to match the shuttle's speed at that altitude (i.e. accelerating from 235 m/s to 435 m/s requires a delta-V of 200 m/s). Per the estimates in the table above, it cost the shuttle 1 km/s of delta-V to reach that altitude and speed. Net benefit of launching from altitude is therefore on the order of only 0.8 km/s... That's 0.8 km/s out of a total of close to 10 km/s required to reach orbit!

Also, reinforcing the rocket so that it can sustain bending loads is non-trivial. According to NASA astronaut Don Pettit's article The Tyranny of the Rocket Equation:

The common soda can, a marvel of mass production, is 94% soda and 6% can by mass. Compare that to the external tank for the Space Shuttle at 96% propellant and thus, 4% structure. The external tank, big enough inside to hold a barn dance, contains cryogenic fluids at 20 degrees above absolute zero (0 Kelvin), pressurized to 60 pounds per square inch, (for a tank this size, such pressure represents a huge amount of stored energy) and can withstand 3gs [vertically] while pumping out propellant at 1.5 metric tons per second. The level of engineering knowledge behind such a device in our time is every bit as amazing and cutting-edge as the construction of the pyramids was for their time.

Admittedly the shuttle's main tank is an extreme example, but one needs only to recall the recent in-flight break-up of a Russian Proton rocket to understand that even conventional rockets don't handle transverse stresses very well… That doesn't mean it can't be done, but it means that launching from a carrier aircraft isn't as obvious an advantage as some might think.

Edited September 6, 2013 by PakledHostage

[Moar Boosters]

I don't think you really need to do all the maths to know the difference between a conventional plane's flight and orbit is so vast you're not really saving a huge amount.

If somebody was to design a 2 craft system that's practical for getting into orbit, you're looking at some of the original space shuttle concepts.

http://www.nss.org/resources/library/shuttledecision/chapter08.htm#intro

That thing would work in theory...... but that's what it'd have to be. A big rocket strapped to an enormous rocket, and that kills most of the useful aspects of Virgin's system such as the ability to land on standard runways, and the fast turnaround of the launch vehicle due to it having simple jet engines. Not to mention it was deemed to expensive even for NASA.