XCOR Rocket Plane Soars into Record Book

>I don't think the breakthrough in cost per pound is going to come from rockets as much as from scram-jets or something more exotic

"Our Universe is a four-dimensional rotating
hypersphere. The rotation creates a centripetal
acceleration which is generally orthogonal to the
Universe's space in every point and not perceived by the
objects of the Universe. However, the centripetal
acceleration, along with the elastic reaction of the space,
causes curving of the space in vicinity of massive bodies.
As a result, in the curved areas the acceleration is not
orthogonal to the space, which appears to the Universe's
objects as gravity."

"Big Spin" Model of Gravity by Sergey Ivanenko

OK, so after your post, I became curious as to how close to "orbital" a spaceplane must be that can make a trip from New York to Sydney (as opposed to the suborbital flights of Shepard and Scaled Composites which travel ~100 miles). I wrote the following to XCOR:

-->Hello, I'm a follower of your work, and
congratulations on your recent record with the
EZ-Rocket. I would assume one of the markets for the
cutting edge space-plane industry is long-distance
passenger transport, say New York to Sydney or
similar. Even though a full orbit of the earth is not
required, would this vehicle have to basically reach
orbital speeds to make such a journey, or could a
sub-orbital vehicle such as yours make the trip and
not have to deal with the re-entry heat issues and
much larger thrust requirement? Thanks and good luck,<---

Their reply:

--> By definition, any vehicle whose trajectory always intersects the Earth's
surface is in a suborbital trajectory, and if it meets the other elements of
the definition, is a suborbital rocket.
Depending on how much use one makes of the atmosphere for range
extension by gliding, long-range point to point transport takes something
on the rough order of 60-80% of the velocity (or about half the specific
energy) of orbital flight. That's way harder than just reaching 100km altitudes
and a bit easier than making orbit.<---

So as I suspected, a craft that could make a flight out of the atmosphere halfway around the world, while technically a suborbital trip, basically needs orbital capability. That is an order of magnitude more difficult and impressive an accomplishment than the bottle rocket shots Rutan and XCOR may be capable of. Like I said in my e-mail to them, I wish them the best of luck, but like I said in this thread, I am far more impressed with NASA's accomplishments and rightly so.

> So as I suspected, a craft that could make a flight out of the atmosphere halfway around the world, while technically a suborbital trip, basically needs orbital capability.

Ahhh... no. Not even close. As the response from XCOR stated, you'd need soemwhere between 60 and 80% of orbital delta V capability; that's between 36% and 64% of the orbital *energy* required. And trust me, making a manned vehicle that can carry a useful payload with a full 100% is *far* harder. An aircraft the size of a Concorde, with 1960's level of structural and propulsion tech, could in theory be made intoa rocket-powered BGV with global range and a moderately useful paylaod. But to be orbital, it'd have to be built like an eggshell from the latest materials.

Global range BGV's, while damned difficult, are *far* easier than SSTOs.

>I am far more impressed with NASA's accomplishments and rightly so

I recently heard
of an actress who was flown
from Australia

to Los Angeles
(that's twenty-two hours flying!)
just for a screen test.

Then they flew her back
Down Under the next morning.
(Twenty-two more hours!)

Sub-orbital planes
may not be as impressive
as orbital craft,

but they'll get business
RIGHT AWAY and the profits
can fund more research.

Apparently you are one of those stubborn ones who can't admit when they are wrong.

You wrote:"And trust me, making a manned vehicle that can carry a useful payload with a full 100% is *far* harder"

According to XCOR, it's just a "bit" harder. According to me, it's also a bit harder. The BIG difference in difficulty is between the suborbital shots they are capable of right now and the suborbital New York to Sydney shot, just as the guy said in his e-mail. That last sentence is my whole point.

"They were simplifying."

ahh, I see.

"How involved have you been in launch vehicle analysis and design? Specifically, single stage to orbit vehicles?"

Is that you changing the subject because I was right? This reminds me of teaching an undergrad. Here let me make it simple for you: On a scale of difficulty, if a suborbital 100km shot is a 1 and an orbital John Glenn flight is a 10, then a New York to Sydney is an 8, much closer to the John Glenn than the Alan Shepard.

As to your question, my doctorate in mechanical engineering dealt with radiation transfer from high temperature rocket exhaust and have consulted for NASA and other companies several times. But that's irrelevant; anybody who can read this thread is able to understand your error.

> On a scale of difficulty, if a suborbital 100km shot is a 1 and an orbital John Glenn flight is a 10, then a New York to Sydney is an 8, much closer to the John Glenn than the Alan Shepard.

The problem is that it's not a linear curve. It becomes exponentially more difficult. A NY/Sydney flight can be done with fairly conventional materials and a decently rugged structure. A single stage to orbit vehicle needs the latest of everything and is an eggshell when finished.

A vehicle capable of Mach 25 flight (orbital velocity) requires 1.6 times as much kinetic energy per unit mass of structure/payload than one capable of Mach 20 flight, and 2.8 times as much as one capable of Mach 15 flight. A rocket powered aircraft capable of Mach 15 can efficiently boost-glide halfway across the planet.

So what you get is this comparison:
Assume your vehicles (orbital and suborbial) each weigh 1,000,000 pounds gross.

Assume each have the same propulsion system (assume LH2/LOX rocket engines like the SSMEs) with an Isp of 450 seconds.

Ignore drag and gravity losses.

To get to orbital velocity (about 7.9 km/sec), the rocket equation says your mass ratio is about 5.99. This means that of your 1,000,000 pound vehicle, 143,061 pounds of it is structure and payload. This means that 85% of the takeoff weight is propellant.

To get to Mach 15 (about 5 km/sec), the rocket equation says your mass ratio is 3.1. This means that of your 1,000,000 pound vehicle, 243,902 pounds is structure and payload. About 76% of your takeoff weight is propellant.

The difference between suborbital global range and orbital is nearly a factor of two in dry weight. This is the difference between carryign a useful paylaod and not carrying a useful payload; between being a structure that can be built (wight effort) and being a structure that can just barely be built (with a *lot* of effort)

And even better: global range for a boost glider can be greatly increased by proper use of airbreathing engines while in the bottoms of the skip-trajectory troughs. This is an option unavailable to orbital vehicles.

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