Recent Posts

Pages: [1] 2 3 ... 10 Next
Lets not forget that with a Mars colony as planned there will be a bunch of full size ITS boosters sitting idle between synods unless they have a job.
Its likely the base booster will be shared and there will be different size/purpose 2nd stages for Mars colony and perhaps smaller ones for LEO/GTO access, but big enough to carry perhaps up to 30 tons to GTO or 50 tons to LEO per launch.

If my memory serves, the plan is ITS booster is to last for at least 1000 launches with something around 100 launches between refurbs. Even if the booster costs US$ 500 million, over 1000 launches that's just half a million per launch in initial costs.

With a massive booster and a fairly light 2nd stage, staging might happen 2000km/h faster while keeping RTLS capabilities, this would give extra DeltaV for the whole stack to perhaps deliver GEO satellites to GEO-500m/s or something similar while keeping full reuse capability.

Its normal to be skeptical, after all SpaceX goals are lofting. But one the eve of the first booster relaunch I would hope most would realize that being a naysayer will look silly if SpaceX achieves their goals, which are hard but are certainly within the realm of possibility.

That or SpaceX will develop a fully reusable raptor 2nd stage, however there's the issue with how many reflights F9/FH boosters will be designed to achieve without refurb, while ITS shoots for something like 10x more flights between refurb, which would easily handle a stack that costs perhaps even 5x as much.
Missions To Mars (HSF) / Re: Station On Phobos
« Last post by mikelepage on Today at 07:02 AM »
I asked a astrogator friend of mine if we needed to come in at Mars winter or summer solstice if we wanted an easy slide into a near equatorial orbit.

He replied with the attached illustration from Bates Mueller and White. It's a pic of envelope of outgoing hyperbolas but it could just as well be incoming hyperbolas. In his words "You can pick any inclination available by rotating around the incoming asymptote."

Great pic, although that doesn't actually answer the question, does it? Your friend appears to have latched onto the inclination part of the question as you did upthread.  We already know any inclination is possible.

One actually has to change the angle of the incoming motion vector relative to Mars motion vector if one wants to influence the final orbit's argument of ascending node, right? and I think you can achieve this with a small burn perpendicular to spacecraft direction of motion/Mars orbital plane some weeks before capture... thus skipping the need to enter large elliptical initial orbit, followed by plane change maneuver at apoapsis.
From where I sit it's all hype.  The fundamental law of information systems stays the same: Garbage in = Garbage out.  ..and I've seen many a good SAP/ERP system ruined by crap data.

That is nothing new, and it predates computer systems.  And the solution is nothing new either, and it predates computer systems - a focus on data integrity through good procedures and processes.

For instance, I'm Certified in Production and Inventory Control (CPIM thru APICS) and one of the critical tasks production and inventory control personnel do is ensure the accuracy of work in-process and inventory records.  Engineering ensures the accuracy of bills of materials (BOM's), purchasing ensures the accuracy of procurement records, and scheduling is responsible for having the right requirements loads.  It's not that difficult, but it does take commitment.

And just as an outside observer, I haven't seen any indications that Tesla or SpaceX have problems with their ERP systems.

Process sensor & instrumentation technology is getting better, faster but not nearly fast enough for Elon's visions,  IMHO.  Sure, robots are a great help on production lines but where they achieve greatest benefit is working alongside a human operator.

I'm not understanding your claim that sensor & instrumentation technology affects ERP accuracy.  Nowadays it's a simple sensor that reads a barcode, or it could just be an operator pushing a button to signal the completion of a part or a change in location for an assembly.

As for robots, I disagree that their greatest benefit is when they work alongside humans.  Robots work best when there are no humans.  But that is OT for this thread...
SpaceX Reusable Rockets Section / Re: Fairing reuse
« Last post by john smith 19 on Today at 06:41 AM »
TBH I've never really understood need for the very rigid, heavy fairings that LV's use.

I've often wondered if you could get by with an inflatable design, soft of like those emergency half circular shelters, but with two edge to edge and both on end.
Commercial Space Flight General / Re: Vector Space Systems
« Last post by ringsider on Today at 06:39 AM »
Truly amazing the attention they draw on themselves for what is basically an empty aluminum tube...
SpaceX Reusable Rockets Section / Re: Fairing reuse
« Last post by john smith 19 on Today at 06:38 AM »
I associate a "hot" landing with a stage that has pushed the rest of the stack to higher velocity or altitude than usual missions.

It will therefor be coming in at a faster velocity. OTOH it had to burn harder on launch suggests it will also have tighter restrictions on how much landing propellant it can carry.

So propellant margins are tight and the terminal landing process is shorter than usual. That means this time round engines really need to start at the first attempt and burn at full planned thrust for the full duration. It's unlikely the landing legs can soak up much of the KE left if the engines do their part fully.

All of which will make for very exciting video.
SpaceX Reusable Rockets Section / Re: When will F9/F9H be retired?
« Last post by Lars-J on Today at 06:35 AM »
There's no such thing as "too big". You mean "too expensive". If an ITS launch is cheaper than a Falcon launch, why would anyone buy the Falcon ride?
That PoV demonstrates yet again how the ICBM architecture has warped space launch.

In every other transport mode except space launch there is the idea of a "right size" for a vehicle to carry a load and what that vehicle should carry.

This is why long distance coaches don't carry swimming pools  :). This is why you could use a panel truck with a pallet load of seats as an SUV people don't.

Only in space launch (where you're going to throw away the vehicle anyway) is bigger always viewed as better.  As long as throwing away most, if not all, of the vehicle is the norm this will continue.  :(

You are quite wrong... The transportation industry is a perfect example of the opposite. Things get delivered in oversized vehicles all the time. All my mail and boxed deliveries are delivered in large trucks. How is that "right size"?  Most people drive alone in a car that can sit 4-8 people. How is that "right size"? Small items get shipped across the ocean in massive cargo ships. How is that "right size"?

No, bulk freight wins out every time there is a choice. For almost every cargo the "right size" is indeed massively oversized. The only reason that you see various sized transports is due to the sheer VOLUME of cargo that allows lots of niches of vehicles, and sizes of those vehicles.

If there is a sufficient volume of space launches, all sizes of launch vehicles will find a niche to be successful. But bulk will always be the more efficient and lower cost way to go.
The odds on bet must be that SX will get some things wrong. The worst case being they are unable to recover the stage.
Wrong. Worst case is that there will be launch faliure.
Literally true, although SX have a history of finding new ways to have a launch failure it does seem a little early for another one, and we know the first stage has functioned flawlessly already, which raises confidence in 50% of the vehicle stages (or 90% of the engines) already.

My focus is always on the customer. From their PoV it doesn't matter if the first stage explodes into a million fragments, provided it happens after stage separation and none of the fragments does any damages to the second stage (even if some of them hit it).
SpaceX Reusable Rockets Section / Re: Fairing reuse
« Last post by Semmel on Today at 06:29 AM »
My main point has always been that the thing he's referring to in the tweet is not just reuse of the first stage.

I am pretty sure it is first stage reuse. It's the one thing that is disruptive of the launch industry. It's the one thing the success of SpaceX will hinge on. I mean not this flight particularly but reuse in general. This flight is the first occasion where proving reuse is possible and maybe even economic. Any other technical challenge like fairing reuse will not determine SpaceXs future. But reuse must work or SpaceX has failed. That's why (in my opinion) musk is talking about fate.
Blue Origin / Re: Blue Origin's BE-4 Engine
« Last post by Steven Pietrobon on Today at 06:22 AM »
The British had the Bristol Siddeley Gamma, which was staged combustion, albeit with a much simpler catalystic preburner.

Gamma was not staged combustion, but gas generator. From

D. Andrews and H. Sunley, "The Gamma rocket engines for Black Knight," J. British Interplanetary Society, vol. 43, pp. 301-310, July 1990.

"The steam/oxygen mixture that drives the turbine is accelerated in conical de Laval nozzles, and the exhaust gas is discharged to the atmosphere or space through the casing and exhaust pipe."
Pages: [1] 2 3 ... 10 Next