SpaceShipThree Question: Could a 2-3 engine design get us to LEO?

[The7thEngineer]

If they designed an extra engine or two into it, could it take people to LEO?

[CitabriaFlyer]

You are going to need a lot more fuel because of the burn duration to achieve the necessary engine.  The second issue is re entry.  I do not know if the feathering wing alone will be sufficient to decelerate the ship from orbital speed.  I suspect you will need some sort of thermal protective system. 

I do think that we will see winged, air launched orbital space vehicles in our lifetimes; however the speeds (Mach 25 as opposed to Mach 3ish), increased fuel and propulsive requirements and associated vehicle size increase, and the increased systems capabilities and redundancies for orbital flight are such that an orbital spaceship 3 will look bigger and likely different than spaceship 2.  It is going to take more than strapping on another couple of engines.

Question for the professional engineers:  If you dropped Dreamchaser from 500knots at 50,000 feet could it make it into orbit?  Intuitively I don't think so.

[butters]

Dream Chaser's engines are only sized for orbital maneuvers including deorbit, comparable to Shuttle OMS (delta-V 305m/s) or Dragon Draco (estimated delta-V ~550m/s).  By comparison, ascent to LEO is ~9500m/s, so not even remotely close.

When considering air-launch SSTO, consider that the OSC Pegasus is a three-stage rocket dropped from a widebody airliner and delivers less than 500kg to LEO.  An SSTO would need a larger carrier aircraft to deliver the same payload.

[hop]

If they designed an extra engine or two into it, could it take people to LEO?

This is what it takes to get a small (maybe theoretically big enough to carry one person) space plane to orbit:
http://www.ulalaunch.com/site/PhotoGallery/galleryimages/images/AtlasV/A5_OTV/av_otv-1_l.jpg

If you want to get a similar mass to orbit, you need about that much rocket.

SpaceShipThree doesn't exist beyond vague rumors AFAIK, so any speculation about it's capability would be premature.

[Sparky]

If they designed an extra engine or two into it, could it take people to LEO?

If that extra engine or two were in the form of a sizable drop stage, then maybe. This was essentially t/Space's plan, only with a capsule. I wonder if a lifting body that the front of the rocket would hurt or help performance.

[Robotbeat]

Hybrids have neither the mass fraction nor the Isp you'd want in order to get to LEO.

It'd be a liquid engine of very different design than their current engine. It wouldn't be a single-stage, either.

And it'd definitely need a substantial Thermal Protection System (much different than their current one which is just a strip of cork or something). That's one of the hardest parts (if not the hardest) when designing a reusable space plane. I wouldn't be a bit surprised if they went with a kind of capsule for an orbital craft. Even if made by Scaled.

[HMXHMX]

If they designed an extra engine or two into it, could it take people to LEO?

If that extra engine or two were in the form of a sizable drop stage, then maybe. This was essentially t/Space's plan, only with a capsule. I wonder if a lifting body that the front of the rocket would hurt or help performance.

I can tell you that a multi-stage rocket, even air-launched, that can place DC into an ISS inclination orbit will mass from 600-1,000K lbs at release form the aircraft, depending on engine choice, propellants, etc.  Given that WK2 can lift about 35K lbs, you will need a launch aircraft ~15 to 30 times larger than WK2.

Our t/Space CXV was a lightweight capsule-type spacecraft that was to mass under 10K lbs; DC is much heavier.

[telomerase99]

Maybe the next lifter should be in the form of a balloon? Can't a balloon lift our space craft higher than 50000 feet?

If we did have a balloon that could lift our space craft to say 100000 feet, how much would that decrease the energy requirements to get to orbit? Where is the sweet spot and why? Is it most important to get to an altitude where wind resistance is less important?

[Lars_J]

Altitude helps, but it is *velocity* that is crucial.

[vt_hokie]

You are going to need a lot more fuel because of the burn duration to achieve the necessary engine.  The second issue is re entry.  I do not know if the feathering wing alone will be sufficient to decelerate the ship from orbital speed.  I suspect you will need some sort of thermal protective system. 

In addition to the aerodynamic and thermal demands on a vehicle that has to fly through a wide range of conditions (including some time in the hypersonic regime), there would have to be a much more substantial RCS system, life support system, communications system, etc, no?

I suppose the HL-20 based DreamChaser is, or could be, the SpaceShipThree that the original poster is wondering about!

[Crispy]

Maybe the next lifter should be in the form of a balloon? Can't a balloon lift our space craft higher than 50000 feet?

If we did have a balloon that could lift our space craft to say 100000 feet, how much would that decrease the energy requirements to get to orbit? Where is the sweet spot and why? Is it most important to get to an altitude where wind resistance is less important?

Going up is easy. Going sideways at Mach 25 is the tricky bit.

[Dappa]

SpaceShipTwo only provides 2% of the energy needed to get to LEO.

[spacester]

Maybe the next lifter should be in the form of a balloon? Can't a balloon lift our space craft higher than 50000 feet?

If we did have a balloon that could lift our space craft to say 100000 feet, how much would that decrease the energy requirements to get to orbit? Where is the sweet spot and why? Is it most important to get to an altitude where wind resistance is less important?

Here's a formula for that:
v = sqrt( ( 2 * G * M )*((1 / R) - (1 / (R + elevation)))
where
v = ΔV savings, km/sec
G*M = gravitational constant
G*M = 3.971E13 N-m^2/kg
R = Earth's radius
R = 6.377E3 km

For elevation 100000 ft:
100000 ft = 30.48 km
ΔV = 0.76 km/s reduction in ΔV to orbit
Which is not nothing, but you need about 10 km/s to get to orbit.

For a VERY low orbit at 180 km the orbital energy is 8.0 km/s but that's after all the losses, which include gravity losses at somewhere between 1.0 and 1.5 km/s

If you could magically remove all wind resistance from a surface launch, you would reduce the ΔV by no more than 0.5 km/s and that's for a vehicle with high drag. Launching at elevation means less savings than that.

So even with a balloon that does better than we can hope, and a magical zero-drag craft, a revolution in physics that removes the gravity losses and with an impractically low orbit, you still need 8.00 - 0.76 = 7.24 km/s of ΔV. And that has to come from the rocket engines and all the propellant needed. There are no more tricks in the bag.

With that, I refer you to the other answers here. What you need is velocity, velocity and more velocity.

[The7thEngineer]

You guys have depressed me.

I don't see people wanting to ride to space on a vertical rocket.

Is there any hope for Scaled future designs carrying people to orbit?

[Ben the Space Brit]

As everyone else has said, in the end, you cannot game the laws of physics with optimism.  No matter how much you believe, you still have to respect delta-V.

There must be:

1) Enough delta-v (engine power and burn duration) to reach orbital velocity and altitude;

2) De-orbit capability - That means another engine for de-orbit and also an RCS system for attitude control out of the atmosphere;

3) The ability to resist the heat and aerodynamic forces of re-entry.  FWIW, I suspect that the fundamental geometry of SS1/2 is unsuitable for re-entry from orbit - Those vertical stabilisers would melt and the wings would be torn off.

FWIW, I've seen nothing to suggest that Scaled have ever envisaged the WK/SS archetecture as being orbit-capable.  The next stage of development is a suborbital intercontinental passenger/cargo carrier.

I've seen plenty of designs that have a basic archetecture of horizontal launch, air-breathing fly-back reusable first stage and a rocket-powered reusable upper stage/spacecraft combo to reach orbit.  However, there are several differences.  In most cases, the carrier/spacecraft seperation occurs at supersonic speeds at the very edge of the atmosphere (~100,000ft) and both elements look nothing like the WK/SS system.  Typically, they look more like the X-33/VentureStar

[Lars_J]

Is there any hope for Scaled future designs carrying people to orbit?

There's always hope. It would be foolish to rule anything out.

There have been lots of plausible ideas and plans for air-launched orbital space planes. The problem is that to make it work well, you need a large carrier aircraft that goes very high and very fast. Think a Concorde, but bigger and faster. It is certainly doable, but it would be a very expensive aircraft to design and build, unless you had other uses for it.

Without such an exceptional carrier aircraft, you have to carry a LOT of fuel with you.

The Russian MAKS project (mothballed in the early 90's) shows how it could be done - it was to be carried by the existing AN-225 aircraft with a massive external fuel tank for the space plane:
http://www.buran.ru/htm/molniya6.htm

It is possible (certainly easier than a single stage to orbit), but still not very easy.

[hop]

I don't see people wanting to ride to space on a vertical rocket.

Why does it matter what they ride on ? The only things that really matter are how much it costs, and how reliable it is.

Is there any hope for Scaled future designs carrying people to orbit?

Sure, but don't assume it won't start on a vertical rocket. If they get serious about building a crewed, orbital vehicle, they'll do the trades and come up with the design that they think gives them the best cost and reliability. Air launch isn't impossible, but it definitely brings some difficult baggage.

[Patchouli]

Hybrids have neither the mass fraction nor the Isp you'd want in order to get to LEO.

It'd be a liquid engine of very different design than their current engine. It wouldn't be a single-stage, either.

And it'd definitely need a substantial Thermal Protection System (much different than their current one which is just a strip of cork or something). That's one of the hardest parts (if not the hardest) when designing a reusable space plane. I wouldn't be a bit surprised if they went with a kind of capsule for an orbital craft. Even if made by Scaled.

Actually you can achieve orbit with hybrid rockets but like solids you end up with a large stack for a given payload.
This was considered for Dreamchaser before they decided on Atlas V due to scheduling.

[jabe]

FWIW, I've seen nothing to suggest that Scaled have ever envisaged the WK/SS archetecture as being orbit-capable.  The next stage of development is a suborbital intercontinental passenger/cargo carrier.

Since The National Geographic special wasn't in Canada I watched the 2 preview clips on the NatGeo channel..and this video shows, at a 1:30 in , a concept i was surprised of.  They spent money making the clip but I hope they weren't serious in the design.  Basically show SS2 in orbit on a space station/hotel...

jb

[Ben the Space Brit]

Since The National Geographic special wasn't in Canada I watched the 2 preview clips on the NatGeo channel..and this video shows, at a 1:30 in , a concept i was surprised of.  They spent money making the clip but I hope they weren't serious in the design.  Basically show SS2 in orbit on a space station/hotel...

Nah, they weren't engineering serious.  Remember that this clip was designed as a drop-jaw illustration for the narration.  One of the objectives of it was doubtless to include objects that the audience would recognise to increase the sense that it was something "just around the corner".  SS2, which is inaccurately viewed as a spacecraft rather than an extreme-altitude rocket-plane (basically a passenger version of X-15), fitted in with those marketing requirements perfectly.

You can be sure that NatGeo's CGI subcontractors had no idea of the engineering and scientific challenges.  Their objective was art, not technical accuracy.

[mlorrey]

Since The National Geographic special wasn't in Canada I watched the 2 preview clips on the NatGeo channel..and this video shows, at a 1:30 in , a concept i was surprised of.  They spent money making the clip but I hope they weren't serious in the design.  Basically show SS2 in orbit on a space station/hotel...

Nah, they weren't engineering serious.  Remember that this clip was designed as a drop-jaw illustration for the narration.  One of the objectives of it was doubtless to include objects that the audience would recognise to increase the sense that it was something "just around the corner".  SS2, which is inaccurately viewed as a spacecraft rather than an extreme-altitude rocket-plane (basically a passenger version of X-15), fitted in with those marketing requirements perfectly.

You can be sure that NatGeo's CGI subcontractors had no idea of the engineering and scientific challenges.  Their objective was art, not technical accuracy.

Yeah, firstly, you would need to give SS2 a new thermal protection system that is orbital return capable. The current TPS is most decidely NOT. This will add mass. Secondly, you will need to change fuels. Probably a LOX/Methane combination, or LOX methylacetylene, something along those lines.
Then you will need a stage behind the SS2 (lets call it a 2.9 or so)... that will also be liquid fueled. Cause SS2 cannot go anywhere near orbit on its own, even with a change in fuels.
All this will add a lot of mass to the vehicle, so you'll need WK2 to bulk up to a WK3.

[mmeijeri]

Secondly, you will need to change fuels. Probably a LOX/Methane combination, or LOX methylacetylene, something along those lines.

Or kerosene/peroxide like Black Horse. Easier to transfer in flight, which removes much of the penalty of wings and landing gear.

[Eerie]

I`d like to see something like VentureStar. Huge aerodynamic fuel tank with wings and some payload. Possibly with a horizontal take-off.

[kkattula]

You guys have depressed me.

I don't see people wanting to ride to space on a vertical rocket.

Is there any hope for Scaled future designs carrying people to orbit?

You might want to take a look at Skylon http://www.reactionengines.co.uk/skylon.html

If the Sabre engine works as advertised, and they get sufficient funding, it could have a passenger capability in 10 to 15 years.

[tobi453]

Hybrids have neither the mass fraction nor the Isp you'd want in order to get to LEO.

Hybrids have a better Isp than solids.

[HMXHMX]

Hybrids have neither the mass fraction nor the Isp you'd want in order to get to LEO.

Hybrids have a better Isp than solids.

But terrible sliver fractions, which means – and the designs confirm – it will take four stages to get to orbit efficiently.  Neither solids nor hybrids have any role to play in routine, affordable, and safe human space transportation, and Burt has always said that (to paraphrase) it is not worth building SS3 unless it contains real breakthroughs.  I happen to disagree with him on that point, but he recognizes that hybrids won't have a place in such a system.

[mmeijeri]

Neither solids nor liquids have any role to play in routine, affordable, and safe human space transportation

You mean hybrids, right? Are reusable solids inherently uneconomical, or is that just the case if you have to recover them from the sea? I'm thinking of a variant on the GTX+GEM idea. What if instead of expendable/reusable separating boosters, you had an integral solid rocket in your ramjet duct for takeoff, like some missiles? Just a wild idea.

[docmordrid]

Hopefully Reaction Engine's SABRE jet/rocket hybrid will work and fill that breakthrough requirement. Tests of a key component, the intake precooler, are scheduled for next summer and should clarify its status.

[HMXHMX]

Neither solids nor liquids have any role to play in routine, affordable, and safe human space transportation

You mean hybrids, right? Are reusable solids inherently uneconomical, or is that just the case if you have to recover them from the sea? I'm thinking of a variant on the GTX+GEM idea. What if instead of expendable/reusable separating boosters, you had an integral solid rocket in your ramjet duct for takeoff, like some missiles? Just a wild idea.

Sorry, you are of course correct.  I've edited the post.  Fingers outrunning brain...

Personally, I believe solids are inherently uneconomical.  First, the propellant costs at least ten times more than liquid fuels of choice, and second, the safety and handling, weight of transportation issues, etc., all make solids unattractive for any low-cost transportation system.  Solids excel at t/w, of course, and even aircraft can benefit from that, but you notice how infrequently we now use such a technology in the RATO role.  There's good reasons why we don't.

[Danderman]

This brings me back to the question of why jet engines aren't used as "Strap-on" boosters for small orbital launchers, like Falcon 1. With a dry weight of a ton or so, and an incredible ISP, a cheap surplus engine like the F-100 should be ideal as a booster for the first 60 seconds or so of flight.

[mmeijeri]

Personally, I believe solids are inherently uneconomical.

Can you expand on how this differs from the economics of solids on EELVs? I understand you don't count EELVs as a low-cost transportation system, but here the solids do appear to be cost effective.

[Lars_J]

This brings me back to the question of why jet engines aren't used as "Strap-on" boosters for small orbital launchers, like Falcon 1. With a dry weight of a ton or so, and an incredible ISP, a cheap surplus engine like the F-100 should be ideal as a booster for the first 60 seconds or so of flight.

Thrust matters at liftoff. Little else. And no jet engine can match a rocket in T/W ratio. So you are better off adding a solid or liquid booster rocket instead of a jet engine.

[Danderman]

This brings me back to the question of why jet engines aren't used as "Strap-on" boosters for small orbital launchers, like Falcon 1. With a dry weight of a ton or so, and an incredible ISP, a cheap surplus engine like the F-100 should be ideal as a booster for the first 60 seconds or so of flight.

Thrust matters at liftoff. Little else. And no jet engine can match a rocket in T/W ratio. So you are better off adding a solid or liquid booster rocket instead of a jet engine.

Cost matters, too. Solids are relatively expensive, and generate significant risks.

[HMXHMX]

This brings me back to the question of why jet engines aren't used as "Strap-on" boosters for small orbital launchers, like Falcon 1. With a dry weight of a ton or so, and an incredible ISP, a cheap surplus engine like the F-100 should be ideal as a booster for the first 60 seconds or so of flight.

It's all down to flight rate.  In the past, people have made a decent economic case for "POGO"-style jet-assist but not unless flight rate is in the RLV range of 30-40 per year.  Of course, WK2 is using jet engines for just this purpose. 

And RASCAL explored a version of the approach as well.

[Jim]

This brings me back to the question of why jet engines aren't used as "Strap-on" boosters for small orbital launchers, like Falcon 1. With a dry weight of a ton or so, and an incredible ISP, a cheap surplus engine like the F-100 should be ideal as a booster for the first 60 seconds or so of flight.

Thrust matters at liftoff. Little else. And no jet engine can match a rocket in T/W ratio. So you are better off adding a solid or liquid booster rocket instead of a jet engine.

Cost matters, too. Solids are relatively expensive, and generate significant risks.

inexpensive in a non reusable strapon use.

[HMXHMX]

Personally, I believe solids are inherently uneconomical.

Can you expand on how this differs from the economics of solids on EELVs? I understand you don't count EELVs as a low-cost transportation system, but here the solids do appear to be cost effective.

EELV solids are one of the more expensive parts of the stack now. The real reason they were used was to allow a smooth gradation in payload capability, but at the time that decision was made in the mid 1990s, the cost was several fold less than today.  I expect, based on my knowledge of the current decision process (which I can't elaborate due to NDAs), the decision would be made differently if ULA was starting over today.

But we were speaking of SpaceShipThree.  I know the goals for that future speculative capability aim at cost per flight and cost per pound much, much lower than EELVs.

[mmeijeri]

inexpensive in a non reusable strapon use.

Are you disagreeing with HMXHMX on this?