-
You missed the point. The fuel needed for landing is equivalent to a larger payload that must be lifted.Think of the Tsiolkovsky rocket equation. You have to lift the fuel you are going to need for the landing
Yes. Think of it. When landing comes, payload and 2nd stage is already lifted and fuel which were used to lift all that is already gone - meaning not that much fuel is needed to decelerate remaining mass for safe reentry speed. After all they are doing it now, so nothing much to discuss here.
There are two possibilities for why it appears to work out for SpaceX:
1) It truly is cheaper to spend more fuel lifting fuel to be able to recover the booster than to build a new booster.
or
2) Their booster is just so much cheaper than their competitors' more expensive systems that they can afford it anyway and still be the cheapest alternative.
That they are doing it now doesn't automatically entail that it is optimal or even a good idea. Just that it works.
-
So take anything a European space agency says with a serious grain of salt, the feasibility analysis is often based in politics and not physics.
Ideally feasibility studies should be grounded in both physics and economics. -
Tepe, if it were just economics I wouldn't see any issue with it, but it is heavily based in politics. The theoretical application process for research grants and projects from ESA should be:
a) Check list of open calls.
b) Submit proposal with consortium based on skills.
c) Choose best candidate
The actual process seems to be more like this:
a) Contact the local representative to get the call modified to target a subject you're already working on.
b) Submit a proposal with a consortium based on geographical divisions and political favour.
c) Hope that no one has more friends than you and your project partners.
But to get back to the original topic:I listen to a bit of some of the hype. Lots of talk about building Hyperloop in tunnels and underwater - that is going to make rescue easy. The ideas are all based on some sort of super computerised network that means you capture a driverless vehicle to the station and when you get out, your seat in a hyperloop is waiting - no time wasted. The thing is they will need the same security as airports. Perhaps more since the concept is just so vulnerable.
We also run high speed trains without security, and someone setting of a small explosive charge near a link between carriages or the locomotive would also cause a massacre most likely... The only place where I've seen the type of outrageous security you suggest is in the US really, and the security for aeroplanes is still a joke at the end of the day.QuoteYou fire a tiny charge that pierces the skin of a passenger carriage at the 900 Km mark of a 1000Km pipe and they have to immediately flood the whole tube with air. They then have to rescue the thousands of people in the tube which could mean some have to drive 900Km at a slow speed back to the starting point. The Hyperloop is down probably for the day.
Wouldn't it be 100 km to the other end point, just to be a bit pedantic
And you'd have to segment the tunnel with airlocks anyway, to have a realistic chance of maintaining a vacuum in the majority of the tunnel when you have to do maintenance for example. So you wouldn't have to pressurise the entire tunnel. Honestly there are enough holes in this thing that you don't have to poke at it with these weak arguments. Pretty much every argument I hear against the hyperloop can be categorised as the following:- The entire tube will collapse if there is a single dent.
- The vehicle is very fragile and we'll need outrageous security measures to keep everyone safe since they'll be killed instantly otherwise.
QuoteThey are now only talking of a 2/3 cost saving over high speed trains, and so by the time it is implemented, the reality could be 3 times the cost of high speed trains. They know what trains cost. The Hyperloop costs are fictional at this stage.
No company is going to release their actual cost estimations since it'd make them vulnerable to the competition if there would ever be an actual project call for it. But no matter what it'd run massively over cost, see the average monorail project to get an idea of how bad these things can get. -
So take anything a European space agency says with a serious grain of salt, the feasibility analysis is often based in politics and not physics.
Ideally feasibility studies should be grounded in both physics and economics.
japanese maglev trains have fully working prototypes that the public can ride on.
as full-sized non-working structural models imaginary, simulated, or theoretical do not cut it.
scientific calculations must be tested in the real world. elon musk needs put his money where your mouth is.
a working prototype, not a lot of test jigs. prove that it works. have it top out at 670 mph (1080 km/h) in the tube
over range of 263 miles (or 424 kilometers) simulated range of Los Angeles to Las vegas. -
You missed the point. The fuel needed for landing is equivalent to a larger payload that must be lifted.
Indeed it can be payload in place of landing fuel/gear. I did not miss any point, Mr.Obvious, I just said that not that much fuel is needed for deceleration. Anyway if it would not be feasible, then they would not even try. After all they are leading rocket scientists, not you or me
Quote1) It truly is cheaper to spend more fuel lifting fuel to be able to recover the booster than to build a new booster.
For sure initial cost of booster refurbishment is much higher as stated, but it will go down w/o doubt:
http://spacenews.com/spacex-says-reusable-stage-could-cut-prices-by-30-plans-first-falcon-heavy-in-november/
Shotwell said it was too early to set precise prices for a reused Falcon 9, but that if the fuel on the first stage costs $1 million or less, and a reused first stage could be prepared for reflight for $3 million or so, a price reduction of 30 percent – to around $40 million – should be possible.
-
For sure initial cost of booster refurbishment is much higher as stated, but it will go down w/o doubt:
How does "without a doubt" fit with that vague Shotwell quote? (fantastic name to have in the rocket business, by the way)
http://spacenews.com/spacex-says-reusable-stage-could-cut-prices-by-30-plans-first-falcon-heavy-in-november/
Shotwell said it was too early to set precise prices for a reused Falcon 9, but that if the fuel on the first stage costs $1 million or less, and a reused first stage could be prepared for reflight for $3 million or so, a price reduction of 30 percent – to around $40 million – should be possible.
Let's see how it goes. At the moment it's just guesses and marketing speech.
Addendum:
It is mainly the "[if] a reused first stage could be prepared for reflight for $3 million or so" part that it all hinges on.
Can they really refurbish a first stage for only $3 million? -
How does "without a doubt" fit with that vague Shotwell quote? (fantastic name to have in the rocket business, by the way)
Come on It's about product life cycle basics. http://productlifecyclestages.com/
-
How does "without a doubt" fit with that vague Shotwell quote? (fantastic name to have in the rocket business, by the way)
Come on It's about product life cycle basics. http://productlifecyclestages.com/
I try again
It is mainly Shotwell's "[if] a reused first stage could be prepared for reflight for $3 million or so" part that it all hinges on.
Can they really refurbish a first stage for only $3 million? -
It is mainly Shotwell's "[if] a reused first stage could be prepared for reflight for $3 million or so" part that it all hinges on.
Can they really refurbish a first stage for only $3 million?
Is it so hard to comprehend that nobody can tell?
-Because nobody refurbished rocket boosters on production scale. Final numbers will be known when they get there. Target is 3$mil, but you know, trade secrets and misleading of customers and competition is going on all around us. We will see.
Anyway for all those LEO constellations to come, lots of launches will be needed. We better pray they meet those numbers so we all can have better and lower cost communications.
-
It is mainly Shotwell's "[if] a reused first stage could be prepared for reflight for $3 million or so" part that it all hinges on.
Can they really refurbish a first stage for only $3 million?
Some of that may be from the history of the Space Shuttle where the engines had to be completely rebuilt because they suffered damage on every flight. NASA ended up redefining cracked turbine blades from a failure to a maintenance problem. If the engines are only designed to be used once, then refurbishment may amount to a complete rebuild.
Presumably SpaceX designed their engines for multiple flights so refurbishing amounts to more testing than rebuilding. This implies that they could get more performance out of them by operating them to destruction.
-
Is it so hard to comprehend that nobody can tell?
Not at all. We are in violent agreement. -
Is it ok to increase both (deficit and debt) to spend in this, now?
Perhaps not, but better this than spend $700 Billion on the military .
Isn't that a straw man fallacy? -
Is it ok to increase both (deficit and debt) to spend in this, now?
Perhaps not, but better this than spend $700 Billion on the military .
Isn't that a straw man fallacy?
No. It’s prioritizing spending.
There is a pervasive political hypocrisy here in the US, where politicos say we can’t afford x (usually education, research, infrastructure spending and the like) while enthusiastically supporting much, much larger amounts of spending on the military industry and various corporate welfare or banking bailouts - the places the lobbying money and/or revolving door cushy after-government-service jobs are.
This graph on the US annual discretionary spending gives some perspective.
-
This graph on the US annual discretionary spending gives some perspective.
Wow. Amazing. For comparison, spending in defence in Spain is about half of the green slice:
source: http://www.sepg.pap.minhafp.gob.es/sitios/sepg/es-ES/Presupuestos/pge2017/Documents/LIBROAMARILLO2017.pdf
-
FYI, these are different graphs. This is an error frequently made, even by the media.
This is total fed spending. It looks much more similar:
https://media.nationalpriorities.org/uploads/total_spending_pie%2C__2015_enacted.png
Tim -
When a country joins the WTO it has to buy into the WTO ideology of "progressive liberalisation" which means that eventually everything must be privatized.
So, unless they had public services before their date of accession, and haven't changed them at all or charged money for them at all, or explicitly carve them out, they have to suffer a death of a thousand cuts.
What people need makes no difference it seems. Its like an inside job to steal the whole planet where they all help one another rip off the public everywhere. -
We also run high speed trains without security, and someone setting of a small explosive charge near a link between carriages or the locomotive would also cause a massacre most likely... The only place where I've seen the type of outrageous security you suggest is in the US really, and the security for aeroplanes is still a joke at the end of the day.
It's almost all just theater to make it look like we're "doing something" to keep people safe. The system is full of gaping holes and it's trivially easy to sneak contraband through. On one occasion I flew from a small podunk airport, the sort where you walk through an old fashioned metal detector then wander out onto the tarmac and climb into a plane, into a major international airport. It occurred to me when I arrived that I was standing within the "highly secure" terminal area having completely bypassed all of the security and body scanners, simply by flying a short distance from an airport lacking all those facilities. It's a joke. -
You can turn this reasoning around quite easely: if there is no demand for a radical breakthrough then it won't happen. Chicken & egg until someone throws serious money at the problem and makes the breakthrough happen. Creating something new often requires solving technical issues nobody has solved before.A first simple check is to see if a project is done by multiple companies (in parallel) or just one and where the funding is coming from.
Another first simple step is to stop and think why no one has done this old idea before:
Has there been some radical breakthrough in maglev technology? No.
Has there been some radical breakthrough in ridiculously large scale vacuum tunnel technology suitable for human carriage over hundreds of km? No.
Has there been some other radical breakthrough in the transport market space? No.
Has there been some other breakthrough in cost reduction in anything to do with this? No. -
You can turn this reasoning around quite easely: if there is no demand for a radical breakthrough then it won't happen. Chicken & egg until someone throws serious money at the problem and makes the breakthrough happen. Creating something new often requires solving technical issues nobody has solved before.
People bitch and moan about dumping money in to force technology to evolve but it worked with LED lightbulbs. When they first appeared on the market they were very expensive, $50+ per bulb. Efficiency mandates and subsidies got the ball rolling and now they are in widespread production, readily available and dirt cheap. Without the mandates many people would have been content to keep using incandescent bulbs, oblivious to or not even comprehending the fact that the total cost of ownership including electricity is far more expensive for the "cheap" incandescent bulbs and the LED tech may not have caught on at all in an entirely free market. People are highly resistant to change and sometimes a visionary has to come in and give something a nudge. -
You can turn this reasoning around quite easely: if there is no demand for a radical breakthrough then it won't happen. Chicken & egg until someone throws serious money at the problem and makes the breakthrough happen. Creating something new often requires solving technical issues nobody has solved before.A first simple check is to see if a project is done by multiple companies (in parallel) or just one and where the funding is coming from.
Another first simple step is to stop and think why no one has done this old idea before:
Has there been some radical breakthrough in maglev technology? No.
Has there been some radical breakthrough in ridiculously large scale vacuum tunnel technology suitable for human carriage over hundreds of km? No.
Has there been some other radical breakthrough in the transport market space? No.
Has there been some other breakthrough in cost reduction in anything to do with this? No.
And sometimes, just sometimes, an idea will always just remain fundamentally impractical.
IIRC there is someone on this forum who is part of one of the top HL design teams who have published very details technical papers on it, and even they admit that the vacuum based HL idea is poorly thought through and basically may not happen.
And make no mistake, you can't separate the vacuum idea from Hyperloop, because without it it's no longer the Hyperloop idea.
A vacuum based passenger carrying intercity HL will never happen, I'll bet you a bitcoin on it. -
FYI, these are different graphs. This is an error frequently made, even by the media.
This is total fed spending. It looks much more similar:
https://media.nationalpriorities.org/uploads/total_spending_pie%2C__2015_enacted.png
Tim
Yes, that is true. The graph I posted is, as I said, discretionary - that is, spending which congress has some say in on a year to year basis versus long germ obligations such as social security, medicare, interset on debt, etc - which must be paid and cannot be prioritized, at least not on a near term basis.
It’s the discretionary spending is what’s relevant to this discussion. -
Without the mandates many people would have been content to keep using incandescent bulbs, oblivious to or not even comprehending the fact that the total cost of ownership including electricity is far more expensive for the "cheap" incandescent bulbs and the LED tech may not have caught on at all in an entirely free market.
The total cost of ownership of LED bulbs is much higher than incandescent bulbs where I am because either burn out in about 6 months due to our dirty power. At least the incandescent bulbs were cheap so replacing them was cheap.
-
Yes, that is true. The graph I posted is, as I said, discretionary - that is, spending which congress has some say in on a year to year basis versus long germ obligations such as social security, medicare, interset on debt, etc - which must be paid and cannot be prioritized, at least not on a near term basis.
It’s the discretionary spending is what’s relevant to this discussion.
Congress, or more specifically the House of Representatives, has a say in all of it. Congress cannot bind itself to a rule that it cannot break.
They play the same kind of word game with "cuts" when they really mean they are not increasing something as much as originally planned.
-
I rather suspect you just buy very crappy bulbs. For decent bulbs quality of power won't matter too much.Without the mandates many people would have been content to keep using incandescent bulbs, oblivious to or not even comprehending the fact that the total cost of ownership including electricity is far more expensive for the "cheap" incandescent bulbs and the LED tech may not have caught on at all in an entirely free market.
The total cost of ownership of LED bulbs is much higher than incandescent bulbs where I am because either burn out in about 6 months due to our dirty power. At least the incandescent bulbs were cheap so replacing them was cheap. -
Do you have a link to those papers or some more specific search keywords to feed into Google?
You can turn this reasoning around quite easely: if there is no demand for a radical breakthrough then it won't happen. Chicken & egg until someone throws serious money at the problem and makes the breakthrough happen. Creating something new often requires solving technical issues nobody has solved before.A first simple check is to see if a project is done by multiple companies (in parallel) or just one and where the funding is coming from.
Another first simple step is to stop and think why no one has done this old idea before:
Has there been some radical breakthrough in maglev technology? No.
Has there been some radical breakthrough in ridiculously large scale vacuum tunnel technology suitable for human carriage over hundreds of km? No.
Has there been some other radical breakthrough in the transport market space? No.
Has there been some other breakthrough in cost reduction in anything to do with this? No.
And sometimes, just sometimes, an idea will always just remain fundamentally impractical.
IIRC there is someone on this forum who is part of one of the top HL design teams who have published very details technical papers on it, and even they admit that the vacuum based HL idea is poorly thought through and basically may not happen.
And make no mistake, you can't separate the vacuum idea from Hyperloop, because without it it's no longer the Hyperloop idea.
A vacuum based passenger carrying intercity HL will never happen, I'll bet you a bitcoin on it.