Mars Direct 2.0

[NSEP]

An interesting presentation by Robert Zubrin about getting to Mars.

 

[Wjolcz]

I'm a bit confused about that electric vs chemical propulsion comparison. Is he talking about nonoptimal transfer with electric vs optimal transfer with chemical?

Other than that I agree. It makes sense to go with conventional chemical propulsion than spend more time and money on something that will be ready to go there in a decade or two.

Edited June 20, 2019 by Wjolcz

[tater]

He can be sorta kooky sometimes, but his intermediate plan makes loads of sense for both the Moon, and Mars given the capability of Starship. Tank it up for a highly elliptical orbit, then dump the biggest thing you can get inside as the cargo.

[Ol’ Musky Boi]

6 hours ago, tater said:

He can be sorta kooky sometimes,

You can say that again. I don't know if he's a genius or completely mad or a bit of both!

I'm not sure SpaceX will go the direction of having a "mini starship" because the additional development costs would be financially prohibitive. Starship is very much designed to be a cheap jack of all trades rocket, and that works well for SpaceX's limited budget. If there is government interest in using Starship and they sink some money into it, then I imagine they might go the other route.

[tater]

1 hour ago, Ol’ Musky Boi said:

You can say that again. I don't know if he's a genius or completely mad or a bit of both!

I'm not sure SpaceX will go the direction of having a "mini starship" because the additional development costs would be financially prohibitive. Starship is very much designed to be a cheap jack of all trades rocket, and that works well for SpaceX's limited budget. If there is government interest in using Starship and they sink some money into it, then I imagine they might go the other route.

Yeah, mini starship makes no sense to me at all. I was thinking more traditional elements of a Mars mission.

If they can put something approaching 100 mt on a TMI, then send a MAV ahead, send a return stage ahead to LMO, then send a transfer/hab/lander.

[magnemoe]

20 hours ago, Ol’ Musky Boi said:

You can say that again. I don't know if he's a genius or completely mad or a bit of both!

I'm not sure SpaceX will go the direction of having a "mini starship" because the additional development costs would be financially prohibitive. Starship is very much designed to be a cheap jack of all trades rocket, and that works well for SpaceX's limited budget. If there is government interest in using Starship and they sink some money into it, then I imagine they might go the other route.

Mini starship make sense for standard satellite launches where starship is overkill. 
an smaller fully reusable ship would be cheaper, less fuel used and easier to handle. 

Not so much for Mars, at NSF forum some say he wanted it to keep his plan true, Musk rater go full kerbal. 

[Guest]

My first thought is... isn’t this redundant as all hell? (“How to get people to Mars using Starship”) SpaceX are building Starship exactly for the purpose of sending people to Mars, that destination heavily influenced the fuel and design choices precisely because they have a good idea how they are getting there, and getting back. 

[Guest]

1 hour ago, magnemoe said:

Mini starship make sense for standard satellite launches where starship is overkill. 
an smaller fully reusable ship would be cheaper, less fuel used and easier to handle. 

I think I saw launch cost estimates saying Starship will be even cheaper than a Falcon and judging from what Elon has said in response about how big Starship will be, (trying to remember the quote: “In the future we will need to go much bigger”) the direction from here is bigger not smaller, pretty sure it’s to capitalise on economies of scale but also to move a meaningful amount of people and cargo. Mars is bottlenecked on multiple levels concerning colonisation, transport being a big one that has a knock on effect for many other fronts.

[tater]

1 hour ago, magnemoe said:

Mini starship make sense for standard satellite launches where starship is overkill. 
an smaller fully reusable ship would be cheaper, less fuel used and easier to handle.

Not really. If the cost of launch is amortized vehicle cost, plus operations and propellants, and that cost is some fraction of a expendable, or partially reusable LV, then it's still cheaper. If the launch cost is low millions, maybe not even 10M, it literally pays to use Starship to loft a single sat.

Bigger is better.

If there turned out to be many payloads in variant orbits, then launch them on Starship on a very large tug bus. 100 mt is a lot of mass to do plane changes with, if most all of it is propellant.

[magnemoe]

22 minutes ago, tater said:

Not really. If the cost of launch is amortized vehicle cost, plus operations and propellants, and that cost is some fraction of a expendable, or partially reusable LV, then it's still cheaper. If the launch cost is low millions, maybe not even 10M, it literally pays to use Starship to loft a single sat.

Bigger is better.

If there turned out to be many payloads in variant orbits, then launch them on Starship on a very large tug bus. 100 mt is a lot of mass to do plane changes with, if most all of it is propellant.

To big is not better. its an reason its loads of vans around even if we have semi trucks

Yes an mini starship would use less fuel but it would be cheaper to maintain because smaller with fewer engines, it could also operate from other pads and be easier to handle. 

And yes this is only relevant if its multiple operators with fully reusable rockets. 
I also agree with Musk in going big from the start. 
 

[tater]

7 minutes ago, magnemoe said:

To big is not better. its an reason its loads of vans around even if we have semi trucks

Large trucks don't work in the same areas. Space doesn't care, they don't have to squeeze into a parking space or driveway

Quote

Yes an mini starship would use less fuel but it would be cheaper to maintain because smaller with fewer engines, it could also operate from other pads and be easier to handle.
And yes this is only relevant if its multiple operators with fully reusable rockets. 
I also agree with Musk in going big from the start.

Bigger is likely better, full stop. Not everything scale in a linear fashion. I have a feeling it's easier to hit the desired ballistic coefficient with a larger vehicle. There's also heating, etc, that might be better with a bigger vehicle.

 

[Guest]

 

It would have been interesting to be a fly on the wall during their design process. I imagine there were a lot of super interesting discussions weighing up priorities and requirements! Without that kind of insight all we can do is guess  

I know a lot of things would be related... like the diameter of Starship probably being determined by the space needed for the engine bells on the Starship Heavy stage... which would have been determined by weight, which would have been influenced mainly by fuel weight both of tanker Starship and the amount needed to takeoff from Mars and have the DV to return to Earth. But there’s also the volume of the fuel! That could have determined the length of Starship as well as the aerodynamics... and change one thing and everything else changes. >_< I wish there was some way to follow the design process!

 

Edited June 21, 2019 by Guest

[natsirt721]

5 hours ago, Dale Christopher said:

I wish there was some way to follow the design process!

All we can do is sit back and bask in the glory of what they created what they aspire to create.  As the saying goes, you don't just change one thing about a (space)ship...

[Guest]

I just thought of something actually... i wonder if these prototype Starships will actually be the tanker variants... 

[tater]

6 hours ago, Dale Christopher said:

I just thought of something actually... i wonder if these prototype Starships will actually be the tanker variants... 

Where "tanker" is defined as the uncrewed, cargo version, yes.

[magnemoe]

2 hours ago, tater said:

Where "tanker" is defined as the uncrewed, cargo version, yes.

Now I suspect they would mount extra tanks in the hold of the tankers to hold 100 ton or something with fuel and oxidizer. An special build tanker might sacrifice one sea level engine for one more vacuum one if this is practical with the new design. The old was designed for more flexibility but with three landing legs and 2x3 engines I suspect they make the bottom of starship around an triangular load bearing frame. Replacing the cargo door with an bolted hatch would also save weight and maintenance. 

As for the prototypes, main question how much work it would be to get them up to production standards. They will not initially have regenerated cooling for one. 

[tater]

47 minutes ago, magnemoe said:

Now I suspect they would mount extra tanks in the hold of the tankers to hold 100 ton or something with fuel and oxidizer. An special build tanker might sacrifice one sea level engine for one more vacuum one if this is practical with the new design. The old was designed for more flexibility but with three landing legs and 2x3 engines I suspect they make the bottom of starship around an triangular load bearing frame. Replacing the cargo door with an bolted hatch would also save weight and maintenance. 

As for the prototypes, main question how much work it would be to get them up to production standards. They will not initially have regenerated cooling for one. 

Initial "tankers" will simply be empty cargo versions.

If they can put 100 mt in LEO, then they can put over 100 mt of propellants in LEO by flying with no cargo. As it stands with expendable upper stages, the bulk of mass to LEO is in fact excess propellant.

[magnemoe]

1 hour ago, tater said:

Initial "tankers" will simply be empty cargo versions.

If they can put 100 mt in LEO, then they can put over 100 mt of propellants in LEO by flying with no cargo. As it stands with expendable upper stages, the bulk of mass to LEO is in fact excess propellant.

Yes, an empty upper stag would work but far from optimal, first stage has to drop second at pretty fixed time to be able to return. Leaving an 8% lighter second stage on its way. 
It might even be better to run an tanker heavy. Load it with 200 ton fuel in extra tanks, First stage has an bit lower TWR, but as it has to drop second earlier boost-back is less so some of this cancel out.
Second stage will be lower TWR and has to burn some of the extra tank fuel to reach orbit but should be able to get say 130 ton up. 

And yes they probably use vanilla cargo lifters on dear moon and probably the first mars cargo missions. 

Back to the prototypes they does not have an orbital refueling option build in either. 
My guess is that they get static displays. How about some wet workshop bar