Hacker News Reader

Comment by k_lander | Hacker News Reader

are blue origins rockets any more reusable than spacex's?

Their sub-orbital rocket "New Shepard" has launched and landed 4 times (i think, could be 3 times), with very minimal refurb in between each launch so far.

So from that perspective, very reusable.

But that's also a sub-orbital rocket. It's only a little bigger than SpaceX's landing legs without a payload[0]. So it might not be the most accurate comparison. Also, they have yet to launch anything else. So it's clearly still early for them as a company.

[0]https://imgur.com/a/gLqsy

New Shepard is shown in this image in between Delta IV Heavy and New Glenn near the middle.

Making a reusable sub-orbital rocket is a solved problem. We call them airplanes.

There are probably two orders of magnitude in complexity between making a reusable sub-orbital, and a reusable orbital rocket.

Yes, but an airplane is fundamentally different. This is a VTVL system. Aside from an obvious size and complexity difference, the launching and landing parts are very similar in suborbital and orbital land (for the most liberal use of the words "very similar"). Hell, if you want to argue semantics, Falcon-9's Stage-1 never gets to orbital velocities. So it's really just that "turning around" part that is the major difference (obviously a massive part, and again, i'm not trying to imply that ANY of this is easy in any way!)

Nobody is saying that they will make a bigger New Shepard with no changes and call it a day. But the knowledge they are learning through the suborbital rockets is going to be useful going forward. And they have a lot of time to learn and experiment here, they are looking at a first launch in the next 4 years (no mention of landing), and they have been developing the engine for this new rocket for a few years already.

An airplane isn't a rocket. New Origins is clearly a rocket, not an airplane. Your comment is waaaaaaay off base. The most salient difference here is that a rocket propels itself forward by using the exhaust gases from burning its fuel as the reaction mass, whereas an airplane uses surrounding air as its reaction mass. New Shepherd can generate thrust just fine in a vacuum (because it's a rocket), whereas an airplane isn't going anywhere.

> There are probably two orders of magnitude in complexity between making a reusable sub-orbital, and a reusable orbital rocket.

Hardly. They've already built all of the necessary control systems, and had multiple successful test flights. Now they just need to scale them up. Admittedly this is not trivial, and I'd put SpaceX as far ahead for this reason alone, but it's definitely not an order of magnitude more difficult, probably just around twice as difficult. And nowhere close to two orders of magnitude!

Wait, Blue Origin has already built all the necessary control systems for flight regimes that their existing rocket can't reach? Hypersonic retroburns are not much like ballistic trajectories that barely touch the edge of space.

My point is that scaling up from sub-orbital to orbital is extremely hard. It's not that far removed from going from airplane to rocket, in terms of complexity.

You're going from having a top speed of Mach 3 to a speed of Mach 27 (Stage separation and max Q at Mach 6 and 5). You're shaving every conceivable weight-adder. You're dealing with a rocket the size of a skyscraper, which crumples in on itself when not filled with fuel.

This isn't AWS, where you scale your app by spinning up a couple new nodes. The difference from a suborbital hop to orbit is increasing your delta-v budget nine-fold.

Well, not it isn't. Their current rocket must have a delta-v of about 2.5km/s, so we are speaking of about 3.5-4x increase. Yet, that's a lot.

But remember their current rocket uses hydrolox. That isn't an easy fuel mix to work with! Russians for example, still haven't managed it.

Reply on news.ycombinator.com