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Comment by sangnoir | Hacker News Reader

> Being able to shoot straight up and fall back down isn't anywhere near as useful or hard as orbit.

Being able to reach space at all is the hard part: so many pieces have to be developed and work well together. Achieving orbit is more evolutionary than from going from 0 to 1. Orbit seems like a such an arbitrary line, amd I suspect once BO achieves it, the bar is going to be arbitrarily raised to "Heavy-lift rockets are the hard part, and only 2 organizations on Earth can achieve it"

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> Being able to reach space at all is the hard part No its not. Teenagers can get to space with model rockets and simple fuels. You can reach space simply by throwing something really really hard, but it will come right back down.

https://www.wired.com/story/a-rocket-built-by-students-reach...

> Orbit seems like a such an arbitrary line

It's not. If your super expensive rocket can't reach orbit, why would anyone bother? Can't deploy sats, can't go to the ISS, nothing.

> You can reach space simply by throwing something really really hard, but it will come right back down.

Is there anything special about boosters, second or third stages or vacuum motors that's tough to crack for an organization that has already managed to reach space under its own steam?

Bigger tanks, more engines and/or higher specific-impulse-fuels are tractable problems to organizations that have already reached space - they know how to do R&D, integration and operations. Getting to space ab initio is harder, and is where most - if not all - failed launch companies have failed.

You ask whether there is something special about orbit vs reaching space. This is a good question.

To be in orbit, a rocket must move extremely fast. The source below says that the energy needed to go to space is only 3% of the energy needed to go to orbit. That means orbit is about 30 times harder than space.

And it gets worse than that because of the rocket equation: to get twice as much kinetic energy requires more than twice the amount of fuel, because you are not just accelerating your capsule, but also the fuel it will need along the way.

So yes, there is a huge difference between being able to reach space and being able to reach orbital velocity.

Source: https://blogs.scientificamerican.com/life-unbounded/basic-ro....

It took about a decade of work to go from the first suborbital rockets to orbit, and even that was in the context of a competitive arms race. It actually took more than a decade but it’s not completely fair to count all of that time since there wasn’t a continuous effort between the V-2 and the US and Soviet rocket programs.

I'd love to fly on Virgin Galactic's space plane, but I think its maximum speed is around Mach 3. To get into orbit you need to reach a speed of at least 27,000 km/h (Mach 22). Huge difference!

My argument wasn't on the orbital potential of suborbital vehicles - rather, I think the odds of Virgin successfully developing an orbital vehicle are better than even. Or more succinctly

  P(achieve orbit|reach space) > P(reach space)

They literally had a Virgin company go bankrupt trying to do that as a business:

https://en.wikipedia.org/wiki/Virgin_Orbit

I’ll take the under

Sorry but no, reaching space is not particularly hard. “Space” is an arbitrary line where the atmosphere is really really thin, and it’s defined pretty arbitrarily by what seems like a round number in an arbitrary system of units (100 kilometers). Orbit is qualitatively different and much less arbitrary to define: it’s when your flight path that no longer intersects the earth’s surface. It’s also the first milestone to actually doing anything useful. And it’s significantly harder than just reaching 100.0000001 km of altitude.

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