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SpaceX launch webcast: Orbcomm-2 Mission [video]

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Re: SpaceX launch webcast: Orbcomm-2 Mission [video]

#431

Post by TeMPOraL »

grkvlt wrote: post #411
hoorayimhelping wrote: post #355

Earlier quoted context omitted.

> Why is this downvoted I can't give the exact answer but if I had to guess, I'd say it's a consistently argumentative attitude under the guise of asking questions. The commenter has asked the same question "what makes this SpaceX thing so special?" at different points of this thread and has gotten many different answers providing a bunch of different view points. They're not trying to get clarity, they're trying to…

Sort of... I knew I would get downvoted, mostly because of my failure at SpaceX cheerleading ;) I actually agree that SpaceX did an awesome thing, and really do understand that its more complicated, and difficult, and challenging, and so on, than what Blue Origin managed to do; yes. My point was more of a "HN loves SpaceX and cannot acknowledge that they might not be the best in the world at everything, ever" thing,…

The key difference is, again, space vs. orbit, i.e. 4). 100km vertical hop is not meaningful for lowering costs of spaceflight. Comparable feats have been done before, as pointed out multiple times in this subthread. You can't just take New Shepard and use it as a first-stage booster; it's a rocket designed for the very easiest component of spaceflight, i.e. going high, and completely unsuitable for putting anything in orbit - which means going very very fast horizontally. OTOH, SpaceX landed an actual booster - a much bigger rocket designed to put payload into orbit - which again, means going very very fast horizontally, and then having to reverse that flight and navigate to a proper landing site. What SpaceX did impacts spaceflight significantly. What Bezos did (and SpaceX before him, and others before them) does not.

Re: SpaceX launch webcast: Orbcomm-2 Mission [video]

#432

Post by lmm »

scrumper wrote: post #414
lmm wrote: post #340

Earlier quoted context omitted.

It doesn't have enough fuel, and keeping more in the booster would mean reducing the payload it could carry. I think most of the ways the landing could go wrong involve the rocket falling over, which wouldn't be recoverable (the fins do nothing at low speed, and the engine can gimbal but only a little bit).

On-pad airbags to cushion a toppling rocket that's had an otherwise near-perfect approach?

Sometimes the pictures lose the sense of scale - the stage they're landing is something like 20 stories high, and the engines alone weigh around 4 tonnes. Also anything you put on the pad has to survive being torched by a rocket plume as it comes in for landing - even the concrete is pretty scorched. So that kind of system would be pretty hard to implement - and even if it were workable, Musk is mainly interested in landing systems that will work on Mars too.

Re: SpaceX launch webcast: Orbcomm-2 Mission [video]

#433

Post by dtparr »

jacquesm wrote: post #372
lmm wrote: post #360

Earlier quoted context omitted.

Yes. How would making that a different engine "introduce a single point of failure for the return part of the mission" that wasn't there already?

Because the return part of the mission relies on nine identical engines right now. So if one fails it is not a problem. But if you replace the central one with a different one that becomes critical for the return mission then you have made matters worse.

For future reference, the return part is made up of 3 burns. The first two use three engines, and the landing burn uses just the one. Coming back, it's obviously much lighter without all the propellant and 2nd stage/payload weight, so it needs much less thrust to reverse course. See http://flightclub.io for more info.

Re: SpaceX launch webcast: Orbcomm-2 Mission [video]

#434

Post by chronic50 »

hughes wrote: post #394
sakian wrote: post #364

Earlier quoted context omitted.

Wish I could. As a Canadian though seems ITAR would block me.

Don't let it stop you from applying. It might stop them from hiring you, but let them decide that. Seriously, if a position interests you, apply. There have been plenty of ITAR exceptions.

> Seriously, if a position interests you, apply. There have been plenty of ITAR exceptions.

No there haven't. Don't get his hopes up.

Re: SpaceX launch webcast: Orbcomm-2 Mission [video]

#435

Post by chronic50 »

hughes wrote: post #394
sakian wrote: post #364

Earlier quoted context omitted.

Wish I could. As a Canadian though seems ITAR would block me.

Don't let it stop you from applying. It might stop them from hiring you, but let them decide that. Seriously, if a position interests you, apply. There have been plenty of ITAR exceptions.

> Seriously, if a position interests you, apply. There have been plenty of ITAR exceptions.

No there haven't. Don't get his hopes up.

Re: SpaceX launch webcast: Orbcomm-2 Mission [video]

#436

Post by lmm »

grkvlt wrote: post #411
hoorayimhelping wrote: post #355

Earlier quoted context omitted.

> Why is this downvoted I can't give the exact answer but if I had to guess, I'd say it's a consistently argumentative attitude under the guise of asking questions. The commenter has asked the same question "what makes this SpaceX thing so special?" at different points of this thread and has gotten many different answers providing a bunch of different view points. They're not trying to get clarity, they're trying to…

Sort of... I knew I would get downvoted, mostly because of my failure at SpaceX cheerleading ;) I actually agree that SpaceX did an awesome thing, and really do understand that its more complicated, and difficult, and challenging, and so on, than what Blue Origin managed to do; yes. My point was more of a "HN loves SpaceX and cannot acknowledge that they might not be the best in the world at everything, ever" thing,…

> I would also maintain that the 100km altitude flight is important - it's the internationally recognised boundary of space - and that the 'first' that Blue Shepherd claimed was valid, since the SpaceX Grasshopper did not cross the 100km Karman line.

Having a flight control mechanism that function outside the atmosphere is valuable/important. Landing a rocket without relying on atmosphere is valuable/important. Gluing those two things together is much less so - like being the first person to climb Everest and swim across the Channel.

Honestly the F9 landing isn't much of a "first" - landing a rocket vertically has been done, and landing the main engines of an orbital launch vehicle so that they can be reused has also been done. What makes it exciting is a) the technical difficulty b) the potential for making things there's actual commercial demand for (satellite launches) much cheaper - and in both those regards Blue Origin's landing isn't comparable.

I suspect the main region for the popularity is that SpaceX has done a lot of community engagement, webcasts and all the rest of it, while Blue Origin has done everything in secret. But I'm fine with that - if it encourages companies to be more open then that's all for the good.

Re: SpaceX launch webcast: Orbcomm-2 Mission [video]

#437

Post by simonh »

fixermark wrote: post #379
ricardobeat wrote: post #353

Earlier quoted context omitted.

Why would they offer a discount? The rocket is not going to fly a second time unless it has the same reliability rating as the first. They might end up offering lower cost launches, reducing the margin, but discounts on Nth-launches don't make sense.

At this point, they have the functional monopoly advantage of being able to set prices where they want them (in terms of having an exclusive technology their competitors do not have; they have competition, but if they can really slash their costs by 50% they have the capacity to set their price ten bucks below the competitions' prices and win). ... but if I understand correctly, one of the points of the reusable rock…

Opening up space to new markets must be an essential component of their strategy. If they charged say 90% of the cost for non-reusable launches but their rockets were reusable, they would only need to manufacture a dozen or so vehicles, plus a few a year as replacements. To maintain economies if scale in their factory, they need to have a sustained production line and that means at even a steady pace, with high re usability they will soon be awash with rockets. They will have to bring prices down just to keep their fleet operating.

Re: SpaceX launch webcast: Orbcomm-2 Mission [video]

#438

Post by vermontdevil »

jacquesm wrote: post #323
ctdonath wrote: post #254

Earlier quoted context omitted.

Could someone clarify the stage one path? Where did it launch, and where did it land, and where did it go horizontally in the meantime?

It flew 100's of kms away from the launch site, flipped around, flew back and landed a mile or so from the launchpad. http://arstechnica.com/science/2015/12/by-making-a-historic-...

Actually 9KM from the launchpad I believe.

Re: SpaceX launch webcast: Orbcomm-2 Mission [video]

#439

Post by rdancer »

lmm wrote: post #341
jacquesm wrote: post #322

Earlier quoted context omitted.

And you suddenly introduce a single point of failure for the return part of the mission.

Can the first stage land with a failed center engine?

It has eight other engines to fall back on, and engine restarts are already normal part of the return flight. Centre engine failure before the final burn starts would certainly be survivable. It's just a question of the software using two or three engines in a symmetrical pattern for a 1/2 or 1/3 of the length of the 1-engine burn. I'm not sure if they could also fire one engine asymmetrically and use momentum and the secondary positioning system of cold thrusters to counter the asymmetry.

I don't think that the software is enabled yet -- SpaceX usually press forward with the main objective first, and flesh out the contingencies later (for example, abort hardware was present during the last failed launch, and it had been tested before, but the software wasn't enabled, and they lost the vehicle).

Re: SpaceX launch webcast: Orbcomm-2 Mission [video]

#440

Post by rdancer »

lmm wrote: post #341
jacquesm wrote: post #322

Earlier quoted context omitted.

And you suddenly introduce a single point of failure for the return part of the mission.

Can the first stage land with a failed center engine?

It has eight other engines to fall back on, and engine restarts are already normal part of the return flight. Centre engine failure before the final burn starts would certainly be survivable. It's just a question of the software using two or three engines in a symmetrical pattern for a 1/2 or 1/3 of the length of the 1-engine burn.

I don't think that the software is enabled yet -- SpaceX usually press forward with the main objective first, and flesh out the contingencies later (for example, abort hardware was present during the last failed launch, and it had been tested before, but the software wasn't enabled, and they lost the vehicle).

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