Author Topic: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 1  (Read 240121 times)

Offline MP99

All this talk of autonomous refuelling seems pretty unlikely, but then I remember this:-

Quote from: http://www.csmonitor.com/Science/2014/0805/SpaceX-to-make-Brownsville-Texas-first-private-orbital-spaceport-video
For SpaceX, the move to build and operate its own launch site carries a range of advantages, not the least of which is the ability to build and apply automated rocket-processing systems as the company develops them.

The company's overarching goal is to provide reliable access to space at significantly lower costs than competitors can offer. One way the company hopes to achieve that is by building reusable rockets, then taking them to the pad, raising them to their vertical position, fueling them, and launching them within an hour with all these steps automated.

However, it seems one element of this that will need manual operations is to get the rocket onto the TEL in the first place - the very thing that will be an issue in barge operations.

cheers, martin

Offline Brick_top

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread
« Reply #161 on: 11/24/2014 10:28 am »
hi everybody, I've been lurking this place and decided to join.

I tried to correct the perspective of the image from the barge to see the scale of the falcon leg span (60~ feet)
« Last Edit: 11/24/2014 03:20 pm by Brick_top »

Online RonM

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread
« Reply #162 on: 11/24/2014 10:55 am »
"Drone ship" is a great name, but in reality this is still a barge and will need to be navigated into place over long transits to the landing aim points. The lack of a pilothouse and its rectangular profile make it certain it will be towed into position by a tug and then detached for the actual landing exercise before being tugged back to port. A tugboat or similar support ship will be positioned not too far away. Knowing SpaceX that part will probably be contracted out.

There's no non-regulatory reason why they couldn't just have it follow GPS navpoints wherever they wanted it. It doesn't fundamentally need a tugboat or anything.

Perhaps not, however, the International Regulations for the Preventing of Collisions at Sea (a.k.a the COLREGS) require that "every vessel shall at all times maintain a proper look-out.." and to use all available means to determine the risk of a collision and take avoiding action as appropriate.  Resolutely following a set of GPS waypoints isn't very likely to be considered a "proper lookout" in any court of law.

They could, however, navigate the "Drone Ship" from a "Support Ship" either tied up alongside or shadowing it from not very far away... like a really, really, big R/C model boat. :)

There is already work to automate container ships. Like drone aircraft, the ships would be remotely piloted from command centers on shore. Each "crew" could operate multiple ships. The proper look-outs for these drone ships would be someone thousands of miles away. There is no reason why SpaceX couldn't do the same thing with the ASDS.

However, given that the sea is a completely different environment to the air, there are very good reasons why, after at least 15 years of "work" (that I am aware of) on various design proposals by various design consultants for various marketing departments of various large companies.. you've never seen anybody build one.

And no one has ever built a reusable rocket before.  :)

A command ship/tug will probably be used. It's the simplest solution.

Offline MikeAtkinson

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread
« Reply #163 on: 11/24/2014 10:59 am »
hi everybody, I've been lurking this place and decided to join.

I tried to correct the perspective of the image from the barge to see the scale of the falcon leg span (60~ feet)

Welcome.

Good first post, SpaceX will be doing very well to get completely within the yellow circle given the 3m positioning accuracty of the Autonomous Spaceport Drone Ship.

Offline pospa

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread
« Reply #164 on: 11/24/2014 11:54 am »
I tried to correct the perspective of the image from the barge to see the scale of the falcon leg span (60~ feet)
Nice. And maybe you could round the numbers 79,93 => 80 ; 135,8 => 136 and add the lenght of landing surface (233 ft ?). That would make it even nicer.  :)
« Last Edit: 11/24/2014 12:04 pm by pospa »

Offline Dave G

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread
« Reply #165 on: 11/24/2014 12:46 pm »
Having now read through this thread, I don't think I've seen consideration of the following: autonomous risk calculations by the vehicle resulting in a late decision to abort RTLS and fall back to this barge platform.

During boostback phase and initial entry phase, the core's avionics could be evaluating its performance and margins, and it could decide that it just didn't have enough of something to make it back to the primary landing site safely, with margin.  In that case, it would punt and divert to the barge landing, which obviously can tolerate a much more risky landing.  Thus you protect the high-value landing site, but don't dump your high-value rocket in the drink.

The first thing to remember is this: Stage recovery doesn't have to be highly reliable.  If the mission succeeds but the stage is lost, its not the end of the world.  For example, if stage recovery only works 95% of the time, that would still make sense economically.  So the margins for reuse don't need to be the same as the margins for mission success.

With all the simulation and testing that will need to be done by that point, I believe the last-minute decision scenario you describe is highly unlikely, probably much less than 1%. 

The most likely reasons to land the stage on a barge are:
1) Payload is heavy.  Not enough fuel to fly back to launch site.
2) FH cross fed center core is too far away from launch site.
3) One of the 9 engines fail, so more fuel is needed to get payload into intended orbit.

All of these scenarios will be known before the boostback phase begins, so I suspect that once boostback initiates, the stage will either make it back to the launch site or be dumped safely in the ocean.

So I could see them keeping one of these barges around offshore even during regular land approaches, so it's there for them to abort to if their fuel margin is low or whatever the performance shortfall is.

Yes, but probably more to cover a single engine failure (case 3 above).
« Last Edit: 11/24/2014 12:57 pm by Dave G »

Offline deruch

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread
« Reply #166 on: 11/24/2014 01:28 pm »
Having now read through this thread, I don't think I've seen consideration of the following: autonomous risk calculations by the vehicle resulting in a late decision to abort RTLS and fall back to this barge platform.

During boostback phase and initial entry phase, the core's avionics could be evaluating its performance and margins, and it could decide that it just didn't have enough of something to make it back to the primary landing site safely, with margin.  In that case, it would punt and divert to the barge landing, which obviously can tolerate a much more risky landing.  Thus you protect the high-value landing site, but don't dump your high-value rocket in the drink.

The first thing to remember is this: Stage recovery doesn't have to be highly reliable.  If the mission succeeds but the stage is lost, its not the end of the world.  For example, if stage recovery only works 95% of the time, that would still make sense economically.  So the margins for reuse don't need to be the same as the margins for mission success.

With all the simulation and testing that will need to be done by that point, I believe the last-minute decision scenario you describe is highly unlikely, probably much less than 1%. 

The most likely reasons to land the stage on a barge are:
1) Payload is heavy.  Not enough fuel to fly back to launch site.
2) FH cross fed center core is too far away from launch site.
3) One of the 9 engines fail, so more fuel is needed to get payload into intended orbit.

All of these scenarios will be known before the boostback phase begins, so I suspect that once boostback initiates, the stage will either make it back to the launch site or be dumped safely in the ocean.

So I could see them keeping one of these barges around offshore even during regular land approaches, so it's there for them to abort to if their fuel margin is low or whatever the performance shortfall is.

Yes, but probably more to cover a single engine failure (case 3 above).

[pure speculation]
Agreed re: reasons for barge recovery once full RTLS has been established.   But I think there may be another reason for close inshore barge stationing.  I remember discussion on this site, though not exactly which thread it was in, of final approach targeting of a landing pad as it relates to range safety (and the Big Red Button).  There were people canvassing the idea that the returning stage might be targeted to close offshore (or a designated crash area), with the final burn or some other mechanism creating a final divert to the landing pad.  If that is indeed a range requirement, the ASDS stationed close offshore may give SpaceX the ability to still recover the returning stage in the event that they can't divert to the pad for some reason. 
« Last Edit: 11/24/2014 01:29 pm by deruch »
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Online Chris Bergin

hi everybody, I've been lurking this place and decided to join.

I tried to correct the perspective of the image from the barge to see the scale of the falcon leg span (60~ feet)

Great first post. Welcome to the site's forum! :)

I may use that in the article I'm going to work later today (if so I'll hat tip you in the image accreditations) :)

Offline llanitedave

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread
« Reply #168 on: 11/24/2014 01:50 pm »

It is much cheaper to send an heli from shore than to keep a boat on standby for days, although I am not exactly sure how far the barge will be.

You're going to need a boat there anyway, to propel the barge.  And the boat will probably have the crane on it.
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Offline Brick_top

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread
« Reply #169 on: 11/24/2014 02:02 pm »
hi everybody, I've been lurking this place and decided to join.

I tried to correct the perspective of the image from the barge to see the scale of the falcon leg span (60~ feet)

Great first post. Welcome to the site's forum! :)

I may use that in the article I'm going to work later today (if so I'll hat tip you in the image accreditations) :)

hi there! thanks that would be cool.

I revised the image a little bit and its more accurate now I think, the circles were a bit elliptical in the last one.

edit - If you want I can modify it to your liking

edit2 - updated again with added accuracy... at least thats what it seems to me

« Last Edit: 11/24/2014 03:14 pm by Brick_top »

Offline sghill

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread
« Reply #170 on: 11/24/2014 02:07 pm »
So the speculation mostly hinged on whether SpaceX was serious about using a floating platform as a LAUNCH pad.

Looks like they were, quite serious.   ;D

Just as serious as a reusable second stage.  How is that working out?

Incredible.  I've never seen goal posts moved that fast.  Better check your zipper, your bias is hanging out.

All this talk of autonomous refuelling seems pretty unlikely, but then I remember this:-

Quote from: http://www.csmonitor.com/Science/2014/0805/SpaceX-to-make-Brownsville-Texas-first-private-orbital-spaceport-video
For SpaceX, the move to build and operate its own launch site carries a range of advantages, not the least of which is the ability to build and apply automated rocket-processing systems as the company develops them.

The company's overarching goal is to provide reliable access to space at significantly lower costs than competitors can offer. One way the company hopes to achieve that is by building reusable rockets, then taking them to the pad, raising them to their vertical position, fueling them, and launching them within an hour with all these steps automated.

However, it seems one element of this that will need manual operations is to get the rocket onto the TEL in the first place - the very thing that will be an issue in barge operations.

cheers, martin

If the rocket no longer needs a TEL, then the issue goes away.  I think this sort of feature is on the critical path for the F9 replacement whenever we hear about it.

Obviously, they'll need payload integration of some sort at the beginning of the launch automation process where the payload provider doesn't have autonomous processes, but the rest could be automated, including the drive from Hawthorne to the launch site if you believe Musk's autonomous vehicle predictions.

For the return trip of a booster that's landed and needs to get back home, elimination of a TEL makes a ton of sense.  You then need a "tender" vehicle connected to fuel hoses and other replenishables that crawls up next to the rocket and plugs in.  That doesn't seem like too much of a technology stretch.  It's just a driving target.

As for other discussions about fuel and nose cap.  The booster doesn't need a full fuel load, it's just getting itself back to shore with no second stage or payload.  Also, is a nose cap necessary? It doesn't need to go very fast on the return trip.
« Last Edit: 11/24/2014 02:19 pm by sghill »
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Offline pagheca

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread
« Reply #171 on: 11/24/2014 02:57 pm »
After reading all your comments, as many of you and other commentators, I really wonder if SpaceX is not moving toward an offshore rig. That would allow them:

- a safe launch pad. Almost no noise or range safety issues
- a safe landing pad. You miss it and you just hit the ocean. No safety concerns for neighbours, no cows running away :)
- a place where maintenance and integration would be possible.
- assuming you have a few of them you can position them to optimize launch costs, saving in land ownership, taxes, etc.
- easy to reach for large shipments
- probably (not sure) you can save in tax,

You have higher salary to be paid, but considering the overall cost of the h/w in the space sector, and the fact that you can still maintain production over land, this may be still convenient.

Offshore rig business has been considered since the beginning of space flight (e.g. San Marco  Project, Sealaunch) and it's a mature market. I read that a storm-proof, state-of-the-art rig cost is <<1/2 billion USD if you want it anew, much less if you recycle an old one.

I'm not saying this is what is going to happen, but just that this cheap barge exercise, if successful, could convince SpaceX to move in that direction.
« Last Edit: 11/24/2014 03:15 pm by pagheca »

Online Eer

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread
« Reply #172 on: 11/24/2014 03:55 pm »
hi everybody, I've been lurking this place and decided to join.

I tried to correct the perspective of the image from the barge to see the scale of the falcon leg span (60~ feet)

Great first post. Welcome to the site's forum! :)

I may use that in the article I'm going to work later today (if so I'll hat tip you in the image accreditations) :)

hi there! thanks that would be cool.

I revised the image a little bit and its more accurate now I think, the circles were a bit elliptical in the last one.

edit - If you want I can modify it to your liking

edit2 - updated again with added accuracy... at least thats what it seems to me

Yes - welcome.

One more useful dimension would be the approximately 100' width of the center rectangle, not including the two 35' wings on either side - would capture what Elon tweated about the dimensions of the deck.

Online meekGee

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread
« Reply #173 on: 11/24/2014 03:58 pm »

Actually, a better approach is what I once brought up in the vertical processing thread.

Instead of the above, the "GSE center/launch mount" is not mobile, but is fixed at center deck.  It can only jack up and down.

Retrieval is done with four smaller vehicles that grab the rocket by the legs, which will have "toe holds" especially for that.

So:

- The rocket lands
- The retrievers grab the toe holds, lift the rocket by an inch, and move it to center-deck over the launch mount.
- The launch mount jacks up, grabs the hold-downs, jacks up some more to take the weight of the legs.
- Somehow, the legs are unlocked
- The retrievers possibly raise the legs
- The launch mount retracts back down, and services the rocket
- The rocket launches.

Fewer connections and less moving mass this way.

A variation of this is how I see first stage processing in a rapid-reuse launch port, except that the stage doesn't launch directly, but has to be integrated with the upper stage and payload.

The emphasis with the barge should be on its implications for payload capacity, and the possibility of fly-back.
The "autonomous" part is secondary.

Clearly station-keeping is left up to a computer, but in the grand scheme of things it does not matter if the rocket is serviced with or without human supervision.  Personally, I'd always want to have a pair of eyes on deck up until just before refueling.   Sensors and even remote cameras can't give situational awareness like a pair of eyes and ears and a nose.  There's a difference between highly-automated and fully-autonomous.

And given that there's a tug nearby, I see that as the preferred way to go.
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Offline savuporo

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread
« Reply #174 on: 11/24/2014 04:10 pm »
After reading all your comments, as many of you and other commentators, I really wonder if SpaceX is not moving toward an offshore rig. That would allow them:
Kwajalein. It had some serious logistical disadvantages.
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Offline pagheca

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread
« Reply #175 on: 11/24/2014 04:38 pm »
Kwajalein. It had some serious logistical disadvantages.

Sure. Can you list them (for offshore rigs, not islands)?
« Last Edit: 11/24/2014 06:03 pm by pagheca »

Offline grahamhewett

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread
« Reply #176 on: 11/24/2014 04:47 pm »
Just thought, wouldn't it be safer to have the supplies for refuelling on a separate vessel? You wouldn't want to explode your ASDS if the landing went slightly wrong!
It would make it a bit more modular - they wouldn't want the fuel etc during the first few landings, the flyback would only happen after ASDS had been shown to work. They can have a few tanks etc on the deck of the support vessel safely out of harms way. The refuelling would be a bit more complicated but the navy has been doing that between two vessels for years.

Graham

Offline sanman

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread
« Reply #177 on: 11/24/2014 04:49 pm »
So how fast can this barge travel, anyway?

And what route would it take when transporting a landed rocket stage back to the mainland? (ie. before flyback is perfected)


If it's returning back from the mid-Atlantic, would it have to round the tip of Florida and then sail to Brownsville?
Or would it instead dock somewhere on the East Coast, and then the rest of the journey is done by truck?


See, this is where something like the Aeroscraft would come in handy.

Offline Lars-J

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread
« Reply #178 on: 11/24/2014 04:51 pm »
So how fast can this barge travel, anyway?

And what route would it take when transporting a landed rocket stage back to the mainland? (ie. before flyback is perfected)

It's a barge... So it won't be fast. Barges are usually towed, I think.

Initially they may also use a ship with a crane to off-load the stage and bring it into port. I don't think they want the stage standing up all the way to port.
« Last Edit: 11/24/2014 05:07 pm by Lars-J »

Offline Jim

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread
« Reply #179 on: 11/24/2014 05:05 pm »

See, this is where something like the Aeroscraft would come in handy.

Concept that doesn't work doesn't come in handy

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