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#101 2018-10-09 06:56:49

Belter
Member
Registered: 2018-09-13
Posts: 184

Re: Looking at the Mars Colony's development, based on Space X & BFR

kbd512 wrote:

The first time I see a successful outcome associated with the first item from that list, SpaceX can concern themselves with everything else required to actually live on Mars.

[thumbs up]

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#102 2018-10-09 18:04:23

louis
Member
From: UK
Registered: 2008-03-24
Posts: 4,918

Re: Looking at the Mars Colony's development, based on Space X & BFR

Rocketry is a mature technology and Space X have already resolved the basics of most BFR requirements in terms of engines, hull construction, propellant tank, guidance systems and reusability. Landing remains a challenge but I think they have solutions.

Surviving on Mars is not a mature technology. The closest we have at the moment is ISS. I think there is so much work to be done in terms of water sourcing, ISRU, life support, propellant production, habitat construction, habitat environmental control, unloading the BFSs, communications with Earth, radiation protection, muscle and bone loss etc that it is mission critical, since it pretty much all has to be in place by 2022, only four years away (and some of it earlier in fact, to meet the cargo BFS launch of 2022 - you need to know what you're taking there).


kbd512 wrote:

The first time I see a successful outcome associated with the first item from that list, SpaceX can concern themselves with everything else required to actually live on Mars.


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

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#103 2018-10-09 18:33:03

kbd512
Moderator
Registered: 2015-01-02
Posts: 2,959

Re: Looking at the Mars Colony's development, based on Space X & BFR

Louis,

No argument about the maturity of SpaceX's rocket technology, but several rough field landings are still a requirement for going to Mars.  Going to and from the moon would be a useful acid test / demonstration mission, too.  All I want is a rigorous flight test program followed by an acid test to satisfy any lingering doubts about the maturity of the selected hardware.  After that's done, Mars here we come.  I also agree completely about the maturity of the tech to survive on Mars, although some of that can and should be tested on the moon first.

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#104 2018-10-09 18:37:54

louis
Member
From: UK
Registered: 2008-03-24
Posts: 4,918

Re: Looking at the Mars Colony's development, based on Space X & BFR

I agree that has to be done and will form one of the largest budget items in the programme.

kbd512 wrote:

Louis,

No argument about the maturity of SpaceX's rocket technology, but several rough field landings are still a requirement for going to Mars.  Going to and from the moon would be a useful acid test / demonstration mission, too.  All I want is a rigorous flight test program followed by an acid test to satisfy any lingering doubts about the maturity of the selected hardware.  After that's done, Mars here we come.  I also agree completely about the maturity of the tech to survive on Mars, although some of that can and should be tested on the moon first.


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

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#105 2018-10-09 20:57:36

Oldfart1939
Member
Registered: 2016-11-26
Posts: 1,719

Re: Looking at the Mars Colony's development, based on Space X & BFR

GW Johnson has long stressed the importance of off-concrete-pad landings. The latest iteration of the BFS has moved in a more realistic direction. Since I joined this website 3 years ago, I too have emphasized rough field landings; it's absolutely necessary before any man flies in a BFS.

Last edited by Oldfart1939 (2018-10-10 11:04:05)

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#106 2018-10-09 21:50:55

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 16,173

Re: Looking at the Mars Colony's development, based on Space X & BFR

BFR is not a rocket as it can go no where once in orbit and that is its problem...Lobing all the other rockets to refuel it before going is a boiloff or explosion with the LOX Methane waiting to happen until we have experience with them...

We would be better off sending up water, excess co2 and creating a fuel creation platform to refuel from. Solar panels on it to power the unit, batteries away from the fuel tanks, using the solar array to shade the fuel while its getting made, cryrogenation of Lox and liquid methane on orbit.

Park the ship, robotic connect the fuel hose connections and fill it up to go...No waiting on orbit for multiple ships and you can go when its time on each mars cycle.

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#107 2018-10-10 03:40:03

louis
Member
From: UK
Registered: 2008-03-24
Posts: 4,918

Re: Looking at the Mars Colony's development, based on Space X & BFR

Hmmm...you'd still need separate oxygen wouldn't you...the fire/explosion risk is still there. And surely the mass would be the same - ie you'd still require multiple BFR trips to LEO - since you are just juggling around different quantities of carbon, oxygen and hydrogen in different configurations.

SpaceNut wrote:

BFR is not a rocket as it can go no where once in orbit and that is its problem...Lobing all the other rockets to refuel it before going is a boiloff or explosion with the LOX Methane waiting to happen until we have experience with them...

We would be better off sending up water, excess co2 and creating a fuel creation platform to refuel from. Solar panels on it to power the unit, batteries away from the fuel tanks, using the solar array to shade the fuel while its getting made, cryrogenation of Lox and liquid methane on orbit.

Park the ship, robotic connect the fuel hose connections and fill it up to go...No waiting on orbit for multiple ships and you can go when its time on each mars cycle.


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

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#108 2018-10-10 17:44:32

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 16,173

Re: Looking at the Mars Colony's development, based on Space X & BFR

Actually removing boil off loss for the tank of the bfr as its not setting there waiting for each bfr to bring up fuel one at a time to fill up a BFR...its not about saving bfr flights to haul up water or fuels its the loses that we can not afford.
This solves the high flight rate of bfrs in a small window and allows for more use of the year to get ready to make fuel.
Instead make all the fuel on orbit in a short time span and fill up the bfr. Now on orbit are the three ships going to mars all near the same time.
Oxygen is supplied from the sabatier reactor to create methane from co2 and Hydrogen after its put through electrolysis which allows you to collect water from the partial reaction and oxygen from the electrolysis. This is the basis of the mars ISPP plant....

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#109 2018-10-10 18:00:32

kbd512
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Registered: 2015-01-02
Posts: 2,959

Re: Looking at the Mars Colony's development, based on Space X & BFR

If you combine electric propulsion with artificial gravity, there's not a dime's worth of difference between getting to Mars in 6 months on loads of chemical propellant versus 6 months on inert gas or iodine.  The only difference is how many propellant flights you have to send up and how much the overall solution costs as a function of all those propellant flights.  BFS may be the right solution for sub-orbital / orbital transport, but the ultimate solution to interplanetary transport is still a real ITV that has the excess dV capability to contend with contingency scenarios.

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#110 2018-10-11 04:35:35

louis
Member
From: UK
Registered: 2008-03-24
Posts: 4,918

Re: Looking at the Mars Colony's development, based on Space X & BFR

I certainly agree we will be moving to other technologies.  For one thing you couldn't create a space faring civilisation without causing huge pollution if you stick with chemical rockets. But chemical rockets are the only game in town for the moment.


kbd512 wrote:

If you combine electric propulsion with artificial gravity, there's not a dime's worth of difference between getting to Mars in 6 months on loads of chemical propellant versus 6 months on inert gas or iodine.  The only difference is how many propellant flights you have to send up and how much the overall solution costs as a function of all those propellant flights.  BFS may be the right solution for sub-orbital / orbital transport, but the ultimate solution to interplanetary transport is still a real ITV that has the excess dV capability to contend with contingency scenarios.


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

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#111 2018-10-11 10:01:19

kbd512
Moderator
Registered: 2015-01-02
Posts: 2,959

Re: Looking at the Mars Colony's development, based on Space X & BFR

Louis,

If chemical rockets were the only game in town, the probes we've sent to visit multiple targets wouldn't be possible.  The kind of propulsion I'm referring to is in-space propulsion, rather than launch from a significant gravity well.  However, the efficiency of electric propulsion has a dramatic effect on the number of launches required to go from orbit to anywhere else that looks interesting.

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#112 2018-10-12 05:07:27

elderflower
Member
Registered: 2016-06-19
Posts: 1,122

Re: Looking at the Mars Colony's development, based on Space X & BFR

You need large thrusts to escape from one gravity well and to avoid becoming a pancake on the surface of the next one. The only developed technologies for these are chemical rockets and atmospheric braking. Nuclear thermal nearly got there and wouldn't need a lot of work to make it feasible. Getting off Mars with an NTR using compressed Mars atmosphere might be a way forward, but use of NTR on Earth is not going to be allowed so you would have to return it to Mars, or dump it somewhere where it can't do any harm.

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#113 2018-10-12 17:22:00

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 16,173

Re: Looking at the Mars Colony's development, based on Space X & BFR

Rockets use a pulse thrust design to lift off from earth with roughly 10 to 15 minutes of durations.

To leave earth a simular push is done as well with the calculated distance to the destination being the determining factor for how long the pulse duration will be. Of course there is the mid and later duration correction pulses to make sure that we end up where we are desiring.

To get into orbit requires a reverse pulse of duration that is based on mass of the ship and the destinations gravitational forces. We can do a burn that uses the planets atmosphere to break the speed but its going to be followed at some point to stabilize the orbit. A slower speed to the destination that land it ahead of the destination would allow for a gravity capture as well.

Then there is the final burn to slow so that gravity can do its work to pull the ship towards the surface. Which depending on mass means no parachutes and lots of fuel to land the ship with retropropulsion.

To go home start at the initial step with the values being altered for the home destination....

For man the planning speed of transit and return are the factors that effect the mission surface duration. With the effects of that transit having functioning issues after return home that we do not have totally analyzed but that we do know what it does if we do nothing to counter it.

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#114 2018-10-12 18:55:16

louis
Member
From: UK
Registered: 2008-03-24
Posts: 4,918

Re: Looking at the Mars Colony's development, based on Space X & BFR

Typo?  Seconds I presume?

SpaceNut wrote:

Rockets use a pulse thrust design to lift off from earth with roughly 10 to 15 minutes of durations..


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

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#115 2018-10-12 20:22:27

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 16,173

Re: Looking at the Mars Colony's development, based on Space X & BFR

Ok run time of engines firing continous seconds...

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