Sub-orbital flights only, to just above the Kármán line.
This seems to be ideal for transport as well? That is, if we're trying to get from Tokyo to NYC quickly, we never want to actually go into orbit, do we?
If BO can demonstrate that the risks of a flight into space are comparable to other hazards we encounter in life (car driving, bungee jumping, heli-skiing, surgery), they're going to have plenty of people (myself included) who want to go.
True in general, although for tourism, you don't really want any horizontal velocity, because you want to land as close as possible to the take-off point.
A suborbital trajectory is an ellipse that intersects the ground, and it will do so twice within less than half the world's circumference. If you can make it halfway around the world, you're orbital.
New York to Tokyo is nearly half that circumference, so the energy required is nearly that of orbit.
(Note: I'm approximating by assuming no forces other than gravity, which is an extremely good approximation for a ballistic rocket. In perpetually powered flight the trajectory can of course take other shapes.)
A suborbital trajectory is an ellipse that intersects the ground, and it will do so twice within less than half the world's circumference. If you can make it halfway around the world, you're orbital.
My experiments with Flappy Space Program contradict this. b^) It is perfectly possible to miss orbit even after a complete circumnavigation. Trajectories are shaped like parabolas, not ellipses.
New York to Tokyo is nearly half that circumference, so the energy required is nearly that of orbit.
Well it's more like a quarter, but even if it were half it would take significantly less energy than orbit.
> It is perfectly possible to miss orbit even after a complete circumnavigation.
Yes, if you have a source of lift, and you're within the atmosphere, then you can circumnavigate the globe without reaching orbital velocities. A ballistic rocket generally has no significant source of lift and spends nearly all of its time in space.
> Trajectories are shaped like parabolas, not ellipses.
All orbits are conic sections: either an ellipse, hyperbola, or a parabola (the limiting case between the two). But a parabolic or hyperbolic trajectory has escape velocity, whereas only an elliptic trajectory is planet-bound. The apogee of the ellipse is locally approximated well by a parabola, which is why for non-orbital mechanics ballistic trajectories are often modeled by a parabola, but all suborbital trajectories are actually ellipses, not parabolas. If the Earth were flat and the gravity vector were constant, then they would be actual parabolas.
Orbital mechanics is very counterintuitive. I recommend Fundamentals of Astrodynamics if you'd like to learn more, or play KSP rather than FSP.
> Well it's more like a quarter
On this you are correct, the map I looked at deceived me. :)
OK, thanks for the knowledge. Given all that, and the fact that there are several ICBMs with ranges longer than Tokyo-NYC, I still suspect that the speed-energy-distance combination will eventually work out for some segment of the travelling public.
Yes, but even one quarter the way around the world turns out to be very close to orbital energy, because your delta-distance per delta-v increases rapidly as you increase energy. Nearly all ICBMs are multi-stage rockets for this reason. Vehicles designed for suborbital tourism like Spaceship Two, Lynx, and New Shepard aren't traveling more than a couple hundred km without a second stage.
Math:
Reaching the edge of space requires 100 km altitude, or 1,000,000 m^2/s^2 of specific energy, which is 1,414 m/s velocity. Redirect that to a 45° angle and you have 1,000 m/s in both the vertical and horizontal direction, which comes close to maximizing your distance. That gives you 200 seconds of flight, which puts you 200 km downrange.
The booster couldn't make a soft landing due to a failure in the hydraulics system.
> “Of course one of our goals is reusability, and unfortunately we didn’t get to recover the propulsion module because we lost pressure in our hydraulic system on descent,” Jeff Bezos wrote in a blog post. “Fortunately, we’ve already been in work for some time on an improved hydraulic system. Also, assembly of propulsion module serial numbers 2 and 3 is already underway – we’ll be ready to fly again soon.”
