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#1 2017-11-02 07:51:40

louis
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From: UK
Registered: 2008-03-24
Posts: 7,208

Why Space X is the best...

https://www.youtube.com/watch?v=bvim4rsNHkQ

Great video showing all the propulsive landing failures leading up to success.  Space X are the best - if at first they don't succeed, they try, try and try again.

Next stop Mars.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#2 2017-11-02 07:57:11

RobS
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From: South Bend, IN
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Re: Why Space X is the best...

It's says a lot that they put together a video of their landing failures, too. They can poke fun at themselves. It is also reminiscent of the reel of exploding rockets that a friend of Musk put together to dissuade him from going into the rocket building business.

By the way, there was a very interesting article in Ars Technica yesterday about alt-right attacks on Space X and how they appear to be attacks really on other entities and Congressmen, because Space X and Senator McCain were not involved in the legislation that is being blamed on them.

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#3 2017-11-02 11:04:37

GW Johnson
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From: McGregor, Texas USA
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Posts: 5,615
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Re: Why Space X is the best...

Remember where most of the inflammatory alt-right stuff comes from originally:  Sputnik,  RT,  and a whole host of other internet trolls.  It is intended to divide us,  and that is precisely the effect it has been having,  for some years now.  Which I personally consider to be an overt act of war,  even though no explosives were involved.  And I consider our government's non-response to this existential threat to be treason.

Meanwhile,  I hope the best of success for Spacex, and that they achieve it before they grow so large as to bureaucratize themselves into paralysis.  Up to now,  they have led the way down paths few yet choose to follow,  and so forced down commercial launch prices to affordable values for the first time in history.  And in so doing,  have shown how truly incompetent NASA and "big space" have become.

GW

Last edited by GW Johnson (2017-11-02 11:07:08)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#4 2017-11-10 16:54:50

RobS
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Re: Why Space X is the best...

By the way, for those who want to see the details of the 2016 Mars plan (the first one with the really big BFR) the whole thing is published here: http://online.liebertpub.com/doi/pdf/10 … .29009.emu . It gives all the prices and even gives an estimate of $140,000 pr tonne of cargo to Mars. That's $140 per kilo to Mars, which means he's talking about launches of cargo to low Earth orbit that is much lower; maybe $30 per kilo!

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#5 2017-11-10 16:59:25

louis
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From: UK
Registered: 2008-03-24
Posts: 7,208

Re: Why Space X is the best...

I always apply a multiple of 4 to LEO launch prices for Mars delivery...just a kind of hunch on my part, but glad to see you are suggesting I might well be right to do so.


RobS wrote:

By the way, for those who want to see the details of the 2016 Mars plan (the first one with the really big BFR) the whole thing is published here: http://online.liebertpub.com/doi/pdf/10 … .29009.emu . It gives all the prices and even gives an estimate of $140,000 pr tonne of cargo to Mars. That's $140 per kilo to Mars, which means he's talking about launches of cargo to low Earth orbit that is much lower; maybe $30 per kilo!


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#6 2017-11-10 20:09:07

3015
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Re: Why Space X is the best...

That presentation suggests a cost to LEO that's even better than $30/kg! If 6 booster flights cost $11M and 5 tanker flights cost $8M like in the presentation, then a booster flight costs $1.83M and a tanker flight costs $1.6M. If a cargo flight costs as much as a tanker one, that's $3.43M to deliver 300 t to LEO, or only $11.50/kg.

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#7 2017-11-11 12:46:56

louis
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From: UK
Registered: 2008-03-24
Posts: 7,208

Re: Why Space X is the best...

That would make sense of the claim of $60 per kg to Mars. $60!  Imagine the profit on a tonne of Mars regolith brought back to Earth...

3015 wrote:

That presentation suggests a cost to LEO that's even better than $30/kg! If 6 booster flights cost $11M and 5 tanker flights cost $8M like in the presentation, then a booster flight costs $1.83M and a tanker flight costs $1.6M. If a cargo flight costs as much as a tanker one, that's $3.43M to deliver 300 t to LEO, or only $11.50/kg.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#8 2017-11-11 20:25:34

SpaceNut
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Re: Why Space X is the best...

Musk very well may keep going towards the goals but one false move or a number of catastrophies and the cash to drive his business forward will faulter just as quick as the success.

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#9 2017-11-12 07:47:52

louis
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From: UK
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Re: Why Space X is the best...

True, it's not a done deal yet. Also, I still believe the UN will try and "cut him off at the pass" as they used to say in Old Westerns. Exciting times!

SpaceNut wrote:

Musk very well may keep going towards the goals but one false move or a number of catastrophies and the cash to drive his business forward will faulter just as quick as the success.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#10 2017-11-12 09:34:06

SpaceNut
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#11 2017-11-12 11:48:00

louis
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From: UK
Registered: 2008-03-24
Posts: 7,208

Re: Why Space X is the best...

I am thinking more of the UN lobbying to prevent human flights to Mars on grounds of contamination.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#12 2017-11-12 14:40:10

SpaceNut
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Re: Why Space X is the best...

If that were the case then all probes to any planet would have been stopped by them long ago as there is almost always some level of contamination on them even with the best of cleaning processes....

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#13 2017-11-14 19:12:53

Antius
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From: Cumbria, UK
Registered: 2007-05-22
Posts: 1,003

Re: Why Space X is the best...

SpaceNut wrote:

A small google for "Nuclear power plant construction cost" yields,

Costs for nuclear power plants are driven primarily by the upfront cost of capital associated with construction. While a natural gas power plant could be constructed for as little as $850/kW, recent estimates put construction of a nuclear power plant at $4000/kW.

I am sure that some plants were constructed in a cheaper manner as this is dependant of size and reactors built at a single site and for the fuel type used.

Solar types have different costs for the construction..
How much does it cost to build different types of power plants in the United States?

There would be also different numbers for off grid builds for any of these and if we had a viable nuclear off grid solution it just might be what I would be going with....

As I noted previously, these things are expensive because they are wrapped in red tape.  Any technology can be ruined by over regulation.  No matter how good it is, it will always be possible to run it into the ground.

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#14 2017-11-14 19:29:32

SpaceNut
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From: New Hampshire
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Posts: 29,310

Re: Why Space X is the best...

So that would make Nasa RED Tape and Space x not......its more than that which makes for expense....

Nuclear vs solar vs other topic posts have been split out into this new topic Please continue there....

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#15 2017-11-17 14:26:49

kbd512
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Re: Why Space X is the best...

Apologies for the drift, Terraformer.  Back on topic.

SpaceX is "the best" at what they know how to do well and they do it cheaper than anyone else.  Now, if we can get someone to force NASA out of the launch vehicle and orbital transport business, then maybe they can focus on doing something useful, like going somewhere we haven't already been.

Now they just need closed loop life support, reusable lander vehicles, a power scheme that can do what they say they want to do, and a LOX/LCH4 plant that can be delivered to Mars.  Nobody has ever done that before, including SpaceX.  My guess is that we still need the government and NASA to develop those things so anyone from Earth can go, even if they're using SpaceX rockets to go there.

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#16 2017-11-17 19:06:43

Antius
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From: Cumbria, UK
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Posts: 1,003

Re: Why Space X is the best...

The LOX/Methane plant is something Musk can do.  Zubrin built one for a few tens of thousands of dollars back in the 1990s.

The power supply is more problematic.  Musk can either take the hit and pay for the mass of the solar power system, or he can team up with another agency and develop something like this:
https://en.m.wikipedia.org/wiki/ELENA_reactor

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#17 2017-11-17 21:35:06

SpaceNut
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Re: Why Space X is the best...

Next to power creation and supply in any form, is the system that creates water and fuels plus Oxygen will need lots of redundancy. Lest we forget once we have the power, water and a sheltering environment we now can have food.
Now for the transition from a Space X Falcon 9 to just what seems to be a few shots of the Falcon Heavy it would seem that Musk is striving for some grater size of the BFR, ITV and supper sized MCT each leaps an bound in size and power to move even greater masses from earth to any destination that we should chose.

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#18 2017-11-18 05:56:05

louis
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From: UK
Registered: 2008-03-24
Posts: 7,208

Re: Why Space X is the best...

He's indicated it will be solar.  Makes a lot of sense, especially when you have such a large cargo capacity: unload, unfold and unleash the power.

Antius wrote:

The LOX/Methane plant is something Musk can do.  Zubrin built one for a few tens of thousands of dollars back in the 1990s.

The power supply is more problematic.  Musk can either take the hit and pay for the mass of the solar power system, or he can team up with another agency and develop something like this:
https://en.m.wikipedia.org/wiki/ELENA_reactor


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#19 2017-11-18 07:32:34

SpaceNut
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Re: Why Space X is the best...

But what makes Space X the Best has to do with an over plan and not just a source of power to make fuel.

So what we have is a fast moving company that seems to achieve at a record low cost, robust in design for reuseability.

The Space X plan for Mars:
https://en.wikipedia.org/wiki/SpaceX_Ma … astructure

http://www.spacex.com/sites/spacex/file … y-2017.pdf

For GW landing the BFR converted from Elon's presentation to raw data:

https://www.reddit.com/r/SpaceXLounge/c … ing_graph/

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#20 2017-11-18 10:19:59

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 5,615
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Re: Why Space X is the best...

As near as I can make out from all of this,  "BFR" is beginning to be the identifying label for the common first stage booster,  and "BFS" is the label for the manned spaceship that is one of the three or four possible second stages.  There don't seem to be labels yet for the tanker or the cargo version of the second stage,  although these are all part of the transportation system that the label "ITS" is beginning to cover.  The fourth second stage configuration may be the point-to-point Earth suborbital transport. It's hard to say,  and that Earth transport is far more speculative at this point.

Also as near as I can make out,  the Mars landing is hypersonic entry at interface speeds up to 7.5 km/s (for reference,  escape is 5 km/s and low orbit is 3.5 km/s).   Entry is aerodynamic hypersonic drag deceleration in a nose-low (inverted) orientation at around 30-40 degrees angle of attack (referenced to the wind direction) to around local Mach 3 (2 km/s) at 5 km altitudes (just about as I expected to see). 

As the vehicle continues to decelerate by aerodynamic drag it rolls about the relative wind vector to a nose high attitude for positive lift away from Mars and starts to climb.  Increasing altitude in glide helps decelerate the vehicle faster,  peaking at about 10 km at about Mach 1 to 2 (hard to tell,  but around 0.2 to 0.4 km/s).  It is near this point the vehicle reverses to tail first (a great deal of attitude control authority needed),  and descends tail first decelerating by drag toward the surface. 

Somewhere under 5 km altitude and just over Mach 1 speeds (near 0.2 km/s),  they start the retropropulsion burn for the final touchdown.  That is what decelerates the vehicle to zero as the altitude zeroes,  in a path that is mostly vertical in this final phase. 

There is no indication at all of an Earth entry path,  but I would presume similar at much higher altitudes (probably coming out of hypersonics at Mach 3 near 15-20 km altitudes).  The final transonic tail-first slide would be longer in duration,  starting from a higher altitude,  but not requiring the final landing burn until fairly low,  similar to landing Falcon-9 first stages right now.  The denser air corresponds to a terminal velocity around Mach 1 or a bit more during that tail slide.  Here on Earth Mach 1 is closer to 300 m/s = 0.3 km/s).

The high-angle-of-attack entry with heat shield entirely replaces the tail-first entry burn they do with Falcon stages.  I find that tail-first entry burn concept the most innovative thing I have seen in decades.  Imagine:  how to enter at orbital-class velocities without any heat shield at all,  and with exposed aluminum (!!!!) structure!  Amazing.

GW

Last edited by GW Johnson (2017-11-18 10:23:16)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#21 2017-11-18 15:38:06

SpaceNut
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Re: Why Space X is the best...

I agree that it seems like Space x is creating custome second stages based on what it is going to be doing as part of the architecture keeping to within the 150 ton limit for design.

I saw that the glide path is simular to that of a brick so the little wings on the end probably are not doing all that much to steer that lander as it heads down into the thicker atmosphere as it looks like it is bouncing off at that level and it fires its retro to stabilize that upward sweep so that the engines in the rear now start to do a retro propulsion landing.

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#22 2017-11-19 10:29:12

GW Johnson
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From: McGregor, Texas USA
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Posts: 5,615
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Re: Why Space X is the best...

Somewhere else (I don't remember where),  I read something written by Spacex that the winglets were added to get a static hypersonic stability,  for a wider range of center-of-gravity positions.  They were forced into this unwillingly,  in order to accommodate a wider range of possible acceptable payload masses. 

Due to the lower gravity,  the shorter planetary radius,  and entry at above-escape speeds,  there is the distinct likelihood of bouncing off the atmosphere into deep space at Mars.  The inverted lift vector acts to hold them to the planet,  until they are below orbit speeds (around 3 km/s).  That's about when they roll about the wind axis to lift upward (away from Mars) for final phases of the trajectory. 

Once out of hypersonics down to simple supersonic,  that's when they climb distinctly upward (from ~5 km to near 10 km) to reduce speed sharply and swap nose-for-tail.  They don't actually do a tailslide the way an aerobatic airplane can,  but the energy management is similar.  The attitude thrusters do the positioning in spite of the aero forces acting to oppose them (which is why they need considerable control authority). 

They end up under 5 km at about Mach 1 falling vertically downward tail first.  That Mach 1 (0.2 km/s on Mars) is the min delta-vee for the landing burn.  0.2 out of 7.5 km/s delta vee is the roughly 3% figure,  from which they claim they get 97% delta vee to land by aerodynamics,  not reverse thrust. 

All in all,  it's a pretty impressive piece of design,  but the landing is going to be even more of a nail biter than JPL's Rube Goldberg stuff with Curiosity.  The whole process is quite short. 

I don't know how they will sense to adjust for the highly-variable density profile with altitude:  according to the Marsgram models,  density varies erratically with season and latitude alone,  by factors up to 2,  totally unlike Earth.  If you don't allow for this,  a nominal model could easily crash you.

GW

Last edited by GW Johnson (2017-11-19 10:35:24)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#24 2017-11-19 19:04:38

kbd512
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Re: Why Space X is the best...

GW,

I think the propellant requirements for lunar, Mars, and Jovian moon missions are considerably divergent.  If that wasn't enough there are issues with long term cryogenic propellant storage in a vehicle with composite tanks, developing / delivering / operating a cryogen manufacturing plant on another planet, and electrical power requirements that exceed all other requirements.  The water on Mars also has to be extracted, transported, and then stored somewhere aboard the ship in considerable quantities.

How much faster and easier would it be to do reentry with throwaway TPS such as fabric covered inflatables or expandables and also limit reentry velocities to orbital velocities so that when reusable TPS becomes practical then have lower peak heating requirements to satisfy?

When have we ever flown something the size of the Space Shuttle without TPS maintenance between flights?

Why do the humans and their cargo have to arrive at the same time aboard the same vehicle?  Doesn't that necessarily mean the vehicle has to be huge and expensive?

If all you have to do is TMI the cargo, then why can't far lighter, smaller, and more fuel efficient electric propulsion systems deliver the cargo to a space station in LMO, like Mars Base Camp but without the pork, and then return to Earth for refueling and refurbishment at ISS?

The humans just need tin can modules to survive the trip.  There's no rule written anywhere saying we can't send cargo in advance of the humans.  Someone has to fund these giant interplanetary transport vehicles and there's a great deal of complication involved in fully reusable systems.  A series of modular technologies for specific uses should be easier to design in a reasonable time frame for reasonable cost.  Here on Earth, we don't send 747's directly to individual destinations where cargo must be delivered.  We use 747's to deliver bulk cargo to the vicinity of where it must be delivered and then smaller delivery vehicles take the cargo the final miles to the ultimate destination.

It took SpaceX something like a decade to achieve regular Falcon 9 flights with reusable boosters.  I know they can do it, but now they want to land something as heavy as the Space Shuttle the same way without the benefit of landing pads.

Since most colonists won't be coming back and exploration mission requirements vary so considerably by target, why spend the money to develop something before we're sure we can get the LOX/LCH4 plant running?  Why not prove that technology works first and then determine whether or not the BFS does what SpaceX and everyone else hopes it will do?

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#25 2017-11-19 20:28:44

kbd512
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Posts: 7,607

Re: Why Space X is the best...

Here's a good presentation on the nature of the Earth / Mars reentry problem for any who are interested:

Aerothermodynamics Course.pdf

That document answers a lot of the "why does NASA do reentry the way it does it" questions.  GW's personal blog also has a lot of good info.  JPL provides much of the atmospheric modeling for the problem.

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