On 19-05-25 15:58 , David Spain wrote:
On 5/21/2019 2:15 PM, Niklas Holsti wrote:

So that's the suggestion. Comments are welcome...


This very type of configuration of Starships has been discussed here
before.

Ah, I must have missed that somehow (which surprises me as I tend to
read all posts). Apologies for being redundant.

A belated web search brings up a couple of YouTube videos of such
proposals. However, in these videos the Starships are connected by a
nose-to-nose cable, which means that the Starship structures are
stressed unnaturally in tension, and not in compression as in my
suggestion where the cables are connected to the aft fins. It is the
fins that IMO make the Starship so intrinsically suitable for a bolas pair.

It is not an unrealistic approach. However I was unaware that
the SpaceX plan called for two Starships to make the journey all the way
to Mars.

One Starship could make the trip alone, but in the 2017 "Making Life
Multiplanetary" presentation (https://youtu.be/tdUX3ypDVwI), starting at
36:52 Musk describes the SpaceX "aspirational" plan as follows:

in 2022: cargo-only missions to Mars with "at least 2" ships

in 2024: two cargo ships and two crew ships.

Later trips involve even larger numbers of ships at the same time.

Musk does not say that the ships travel at exactly the same time.
Constraints on the number of Tankers or the Super Heavy launch rate may
mean that some time (a week or two?) passes between full retanking of
the first Starship and the full retanking of the second Starship. But
waiting a week or two in Earth orbit would not be a large increase in
the overall trip time of the first Starship.

Two Superheavys (or whatever SpaceX is calling the BFR these
days) where planned but one of them was not a Starship destined for Mars
but a fueling pod for the Starship that was. That's the plan I remember.

Super Heavy is the BFR first stage (booster). Starship and Tanker are
two versions of the second-stage-and-ship (BFS).

At 27:29 in the video Musk explains the tanking of a Starship in Earth
orbit. He ends up with five Tankers (five Super Heavy + Tanker launches)
to fully refill one Starship. At 33:51 Musk shows four Tankers for a
Mars trip. So five or six Super Heavy launches for one Starship to Mars.

But frankly I think Mars is a long way off. In fact the Moon is becoming
a major distraction. And that actually makes sense since all this
hardware can be tested out far more easily on lunar missions.

Yes indeed, so why would it be a distraction? If you mean the Yusaku
Maezawa trip around the Moon, it does not require the Super Heavy +
Starship + Tanker system to do anything that a Mars trip would not
require. The only major difference that comes to mind is that a
shorter-duration life-support system could be used on the round-the-Moon
trip, with less recycling than during the longer Mars trip. But that
does not seem to be a major distraction.

There is a
push within NASA to refocus on the Moon and a lunar base, by any means
possible. If that means contracting with private enterprise to do it, so
be it. We will have to wait and see how Starship does in this regard.

I hope that SpaceX does not try design a different system for NASA's
Moon plans. Building a SpaceX version of, say, the Blue Origin Moon
lander _would_ be a distraction. Unfortunately, as I understand NASA's
current Moon plans, Starship does not fit -- it has no need for the
LOP-G, nor does it fall apart into the multiple "elements" (transfer,
lander, returner) of the NASA relay-race.

I think Starship will focus on P2P
suborbital trajectories first to establish launch and return procedures
that must work anyway. Then a push to orbit, then a push beyond. Opening
out the envelope becomes easier the further along the curve you get.

Yes, as Musk has explained and as the "Starhopper" is close to start
doing (although very sub-orbital :-).

What is interesting, to me, is how much
SpaceX is going to rely on automation before committing crew to the
Starship. At what point will they crew the vehicle? After it completely
passes all P2P and orbital tests or before? Will crew be considered an
essential part of Starship operation or not? (i.e. will Starship require
pilots or provide crew with a flat screen they can follow the action
on?) If the past is any indication I'd say no. At least not in the
initial stages.

AIUI the Tanker will be uncrewed, as will the cargo missions to Mars, so
I don't see why the Starship should require a crew.

Your bolas configuration could be tried out in LEO.

Indeed (and as I said).

If such a plan were
part of a SpaceX requirement this would make a lot of sense.

"Requirement"? From whom?

SpaceX will surely test the Starship's endurance in space conditions and
it must be easier to do that in Earth orbit than in deep space. But
perhaps some deeper orbits will be tried, too, for radiation soaks.

It could
provide an orbital gravity lab "on the cheap" in the sense that it
doesn't require "bending steel" that a specialized orbital lab would.

That's the nice thing about the Starship. It is big enough to be a "home
on wheels", for traveling and living in.

But you bolas configuration points to a far far deeper question than the
mere mechanics of generating artificial g in space.

The data points we'd get from the physiological effects of long term
operations on the lunar surface might also make the need for a gravity
lab moot. If humans can do "fine" in lunar gravity, there would be no
rational supposition that Mars would be worse.

"If", yes. However the trip from Earth to Mars would still be several
months of zero-gee, which currently is seen as debilitating upon sudden
transition to one gee. But perhaps it will turn out to be OK for a
sudden transition to Martian 1/3 gee.

--
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
. @ .