Colonization Discussion Thread (split from SpaceX)

[DAL59]

15 hours ago, HebaruSan said:

Looks like that's paywalled. (I assume you don't mean the pair of Hohmann transfers on the first page.)

https://www.researchgate.net/publication/238632415_Mars_Free_Returns_via_Gravity_Assist_from_Venus

[tater]

I'm unsure I see the point of free return if the goal is a colony. Colonial transportation is not going to have 1 empty crew vehicle for every full one, that doubles the cost. Any failure mode where free return is desirable (for a short trip like the Moon), it's likely not going to matter. If life support is hosed, they die. If propulsion is hosed, they get to wave at Earth passing by (then at some point they die).

[sh1pman]

2 hours ago, tater said:

they get to wave at Earth passing by (then at some point they die).

Not necessarily. Another ship can rendezvous with them near Earth. Kinda like catching an asteroid in KSP.

[tater]

59 minutes ago, sh1pman said:

Not necessarily. Another ship can rendezvous with them near Earth. Kinda like catching an asteroid in KSP.

What does the next orbit look like after the free return? They're stuck making another complete round trip, but what if earth is not there on orbit 2?

[sh1pman]

Just now, tater said:

What does the next orbit look like after the free return? They're stuck making another complete round trip, but what if earth is not there on orbit 2?

Next orbit doesn’t have to happen. If people can be transferred (in a reasonable time) to the second ship, it can then undock and brake into Earth orbit. It needs at least 4.2 km/s for the initial rendezvous, and then 1.1 km/s more to brake into a highly elliptical Earth orbit. Then burn a little at apogee to bring perigee into atmosphere.

How much dv does a full BFS have? 

[tater]

46 minutes ago, sh1pman said:

How much dv does a full BFS have? 

I want to say ~9km/s.

The problem is that it first has to match the velocity of the returning BFS. Direct entry from Mars is above this. A lunar return is at what, 11-12 km/s? So it seems like it should use all (or nearly all) the props just to match.

[sh1pman]

1 minute ago, tater said:

I want to say ~9km/s.

The problem is that it first has to match the velocity of the returning BFS. Direct entry from Mars is above this. A lunar return is at what, 11-12 km/s? So it seems like it should use all (or nearly all) the props just to match.

If it’s completely refilled in LEO first, it should have enough fuel to match and then brake. Apollo was 11 km/s, so let’s say it’s 12 km/s from Mars. 12-7.7=4.3 km/s to match. Then at least 1.1 km/s to re-capture into elliptical orbit. 4.4 km/s left for maneuvers and landing.

[Mad Rocket Scientist]

36 minutes ago, tater said:

I want to say ~9km/s.

The problem is that it first has to match the velocity of the returning BFS. Direct entry from Mars is above this. A lunar return is at what, 11-12 km/s? So it seems like it should use all (or nearly all) the props just to match.

I ran the numbers on this a while ago, assuming 375 s isp, it has 9689.63 m/s.

That is with a 85t dry weight, and Elon Musk said it would be 75t with some increase. He also said the Isp would be improved by 5-10 s. The slides from the presentation said 85t, but the propellant mass stated in the slides would give the same mass fraction (propellant/wet) of ~0.93 as the 2016 ITS, which makes me suspicious of the numbers.

Edited September 6, 2018 by Mad Rocket Scientist

[Adstri]

It's going to be expensive constantly sending supplies to the Moon or Mars.

Well, not constantly, but every few months at least.

Waiting for transfer windows will be difficult.

Edited September 18, 2018 by Adstriduum

[sh1pman]

Some good points about colonization of outer space and its legal implications.

 

[tater]

1 hour ago, sh1pman said:

Some good points about colonization of outer space and its legal implications.

Yeah, the Outer Space Treaty is nonsense and should be flatly ignored by spacefaring nations.

[MinimumSky5]

Let's not start ignoring treaties, it sets a bad precedent for the more volatile world leaders. Let's instead renegotiate the treaty to something more relevant to space colonisation. 

[kerbiloid]

The Outer Space Treaty, 1967.

Spoiler

... and sci-fi of that time

 

[Green Baron]

Ignoring the treaty would be short sighted and will start the same destruction in space that we have on earth, not only by the above named persons but also and specially by private companies.

We're all friends :-)

[tater]

On 11/2/2018 at 4:12 AM, MinimumSky5 said:

Let's not start ignoring treaties, it sets a bad precedent for the more volatile world leaders. Let's instead renegotiate the treaty to something more relevant to space colonisation. 

If people ever end up living in space in a self-sufficient way (a LONG time off), any such treaty is worth exactly nothing. Enforcing it requires an ability to enforce it. All such arrangements are implicitly supported at the point of a gun. Got no space marines? Then it's nonsense.

 

[Green Baron]

It is a question of attitude and culture. Progress isn't about guns and fighting. It is about cooperation and sharing and we should get back to that because it has made us strong. Treaties can help, if people stick to them. If they ignore them we will have controversy.

Imo.

Edited November 7, 2018 by Green Baron

[tater]

4 minutes ago, Green Baron said:

It is a question of attitude and culture. Progress isn't about guns and fighting. It is about cooperation and sharing and we should get back to that because it has made us strong. Treaties can help, if people stick to them. If they ignore them we will have controversy.

Imo.

The few countries that can actually move humanity into space have the only opinions that matter in the short term, and the people who end up living there will have the only opinions that matter in the long term.

If a business wants to own a rock, I say they should be able to. This treaty (and the UN in general) is a relic of the Cold War, and particularly when neither side knew who might win.

The bits about WMD in space are fine, as those related to earthly, geopolitical concerns. The bits about ownership need to go, or be seriously revised to not require any terrestrial government interaction at all.

[Spaceception]

7 hours ago, Green Baron said:

It is a question of attitude and culture. Progress isn't about guns and fighting. It is about cooperation and sharing and we should get back to that because it has made us strong. Treaties can help, if people stick to them. If they ignore them we will have controversy.

Imo.

Yes, but it'll be hard to do any enforcement for a treaty when communication alone can be minutes or hours away. And best case, actually going there would take several months, with time for them to prepare for your arrival (in case you're still trying to enforce it). How can anyone realistically keep control of a colony? Let alone be able to take care of its day to day needs? Maybe we'd be able to keep hold on the Lunar colonies, but even that could be a stretch.

You probably know all that though But, due to that, I don't see anyone being affected by the treaties caring about them once the colony is strong enough to take care of itself. They will want sovereignty.

I agree with tater though, that the ban on WMD should stay, but ownership of "land" in space will need heavy revisions. Possibly another bureaucratic layer of humanity, where there are loose territories in space, and those are handed out through permission of a nearby power, like Earth, or Mars for example (^^^ I'll cut this part if it's too much).

Edited November 8, 2018 by Spaceception