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SpaceX launch webcast: Orbcomm-2 Mission [video]

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

#151

Post by gozur88 »

dmoy wrote: post #35
kibwen wrote: post #27

Earlier quoted context omitted.

Completely amazing! I'm sure I heard a "holy shit" or two there in the audience. :) EDIT: One question for the rocket scientists here: exactly how reusable do they expect these returned first stage rockets to be? What is the process of certifying that a returned rocket is fit to fly, and what components are most likely to need repairing/replacing with each launch?

A follow-up question to that would be - how much $$ do you save per launch by reusing the first stage?

Depends on the procedure they ultimately decided to use for the prep. Originally the the shuttle main engines had to be taken apart, with every part inspected before the next launch. If they have to do something like that there's not much point.

But if they can get it to point where it's a matter of gassing it up for the next flight, that's a huge savings. Fuel is a few hundred grand for a rocket that costs sixty million dollars. It's nothing, basically.

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

#152

Post by TeMPOraL »

[deleted] wrote: post #149
TeMPOraL wrote: post #127

I join in congratulating SpaceX for this awesome achievement. It's like, holy fuck, they landed the rocket AND deployed 11 satellites, all in a single Pomodoro! I also want to commend them for a few minor things: - a real-time stream from landing (as opposed to holding it and releasing footage few days later, as before) - a real-time stream from satellite deployment, with a camera placed so that we could see everythi…

[deleted]

I'm not implying that they were holding back on purpose, but I did not expect the quality of the whole streaming event to go up so highly. It feels different than before.

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

#153

Post by cornholio »

grkvlt wrote: post #130
JshWright wrote: post #117

Earlier quoted context omitted.

New Shepard is able to make several compromises that make landing _much_ easier. New Shepard doesn't have to get anywhere close to orbital velocity, so it can use a far less powerful engine. That means it can throttle down far enough to hover. That is a _huge_ advantage over Falcon 9, which must time the landing burn perfectly to hit 0 velocity at the exact moment it touches the ground. They're in the same club like…

But the F9 first stage doesn't get to orbital velocity, either, remember. The achievements are comparable, despite the fact it makes SpaceX come second. Blue Origin was first with a VTOL rocket stage, as part of a space system.

Sure, Bezos gets the "first rocket that went to 'space' and landed vertically" prize. It might even be cool sounding for the laypeople who really don't know what values 'space' can take.

But it's not what matters, in fact it's irrelevant, was not a disputed trophy, and won't be mentioned 50 years from now.

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

#154

Post by FeepingCreature »

PhilWright wrote: post #150

If SpaceX is so much cheaper than everyone else, how come they launch so infrequently. Seems like they should be launching every month but they are nowhere near that.

They actually used to be near that, but the accident grounded them for half a year.

Ultimately they're limited by available manpower and production capacity.

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

#155

Post by TeMPOraL »

vermontdevil wrote: post #147
TeMPOraL wrote: post #127

I join in congratulating SpaceX for this awesome achievement. It's like, holy fuck, they landed the rocket AND deployed 11 satellites, all in a single Pomodoro! I also want to commend them for a few minor things: - a real-time stream from landing (as opposed to holding it and releasing footage few days later, as before) - a real-time stream from satellite deployment, with a camera placed so that we could see everythi…

Agreed. Loved the data feed on the video. The tension built up as the indicatior neared the "landing" hash mark.

I had to stay longer at work and was late to the event. My first question, even as the YouTube link loaded, was... "Did they land it yet?", followed by "When are they landing?". Lo and behold, a nice progress bar saying - grab your popcorn, we're about to land now!

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

#156

Post by JshWright »

grkvlt wrote: post #144
JshWright wrote: post #117

Earlier quoted context omitted.

New Shepard is able to make several compromises that make landing _much_ easier. New Shepard doesn't have to get anywhere close to orbital velocity, so it can use a far less powerful engine. That means it can throttle down far enough to hover. That is a _huge_ advantage over Falcon 9, which must time the landing burn perfectly to hit 0 velocity at the exact moment it touches the ground. They're in the same club like…

I guess it's like Hilary and Tenzing being the first to climb Everest, and then someone else (can't remember who it was) coming along and doing it without supplementary oxygen. Just because that was harder doesn't detract from the fact that Hilary and Tenzing were first and anyone else is just joining the ever-growing club of Everest summiters. Now, if you want to invent an extra category of 'first VTOL landing for a…

Ok, in that case, SpaceX was 'first' to land a VTOL rocket with Grasshopper... unless you want to invent an extra category of "first VTOL landing for a ground launched rocket that crossed an arbitrary altitude threshold before returning at terminal velocity".

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

#157

Post by jacquesm »

InclinedPlane wrote: post #136
dmoy wrote: post #35

Earlier quoted context omitted.

A follow-up question to that would be - how much $$ do you save per launch by reusing the first stage?

Lots. There's really not a lot of costs that can add up for reuse of these stages. It'll require a bit of cleaning up, a few new bits and pieces replaced and added, and a lot of inspection work. But most of the cost of the stage is in manufacturing the engines and tanks, so it should add up to enormous savings, even if it's relatively costly to reuse each stage compared to the theoretical limits. Edit: the flip-side…

And with the amount of redundancy built in they might even go with 'acceptable loss' in terms of engines that cut out early in flight. Which makes you wonder how many engines they could lose and still complete a mission.

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

#158

Post by mikeash »

jacquesm wrote: post #135
mikeash wrote: post #128

Earlier quoted context omitted.

They're already insanely cheap compared to most competitors. This should take them to being ludicrously cheap.

Let's see who tries to imitate them and do a re-use, some real competition is what's needed next. Now for second stage re-use ;)

I think SpaceX is sufficiently motivated by their man at the top that they'll keep doing great things even in the total absence of competition. But it would still be great to see others go this way, to see different approaches tried and such. It sounds like some other launchers were looking at reusability plans before (Ariane had plans for some wacky thing that would fly back just the engines) but now that it's been demonstrated to work I imagine it will become much more serious.

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

#159

Post by oroup »

cornholio wrote: post #71
jacquesm wrote: post #41

Earlier quoted context omitted.

NARS but probably comparable to shuttle engines and body.

The Shuttle engines operate on hydrogen which burns very cleanly. RP-1 will leave the engine dirty with coking, so they definitely need to clean re-assemble each engine. On the other hand, the solid boosters of the Space Shuttle were severely damaged by the impact and corrosion of the sea water, after "recovery" they were essentially a source of parts for new boosters. Overall, I really hope they can improve re-usabi…

The hydrogen in the Space Shuttle Main Engine creates embrittlement in the alloys of the engine. [1][2] The launch sequence also involved running the engines at 104.5% of rated capacity. [3] Before Block II of the engines, the turbopumps needed to be disassembled and rebuilt between flights. [4]

I have no real idea how significant coking of the Merlin engine is, but the SSMEs were hardly "clean".

[1] https://en.wikipedia.org/wiki/Hydrogen_embrittlement [2] http://www.tms.org/Superalloys/10.7449/1991/Superalloys_1991... [3] http://www.interspacenews.com/FeatureArticle/tabid/130/Defau... [4] http://www.nasa.gov/sites/default/files/174534main_ssme.pdf

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

#160

Post by FeepingCreature »

jacquesm wrote: post #108
cmsmith wrote: post #103

Earlier quoted context omitted.

Maybe there was a secondary thruster somewhere to provide some separation. I went back and recorded the release speed (km/hr), altitude (km) for each drop: 25960 626 25954 627 25950 628 25944 630 25937 632 25935 632 A circular orbit at that height is about 29000 km around; 25 km/hour of difference between release 1 and 6 would give them a separation of 6 degrees longitude/day, or ~50 days until the faster satellites…

The satellites themselves usually have small thrusters but I'm not sure what kind of orbital change the can effect, usually they are there for detailed maneuvering and to boost the satellite to a slightly higher orbit as it decays. When it runs out of fuel it dies so you'd try to use as little of that as possible during launch.

Even a small difference in orbits adds up over time. You don't need much fuel for orbital adjustments, as long as you're staying in the same plane.

Say one satellite's orbit is a bit smaller. That means that, over time, they will naturally drift farther and farther apart, until they end up on different sides of the globe. At that point, just raise the smaller orbit slightly.

Kerbal Space Program is really good for understanding stuff like this.

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