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Two Starships in "bolas" rotation



 
 
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  #1  
Old May 21st 19, 07:15 PM posted to sci.space.policy
Niklas Holsti
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Posts: 100
Default Two Starships in "bolas" rotation

The SpaceX plans for the first Mars trips involve two Starships making
the trip at the same time. The SpaceX videos show a Starship flying
alone, in a fixed attitude (pointing away from the Sun) thus in free
fall. From other sources there is some concern that a multi-month
weightless trip may incapacitate the pilots and passengers, for example
resulting in blurred vision when they are again subjected to
acceleration or gravity. Here I propose a possible solution: cable the
two Starships together in a nose-to-nose attitude and rotate them to
provide simulated gravity during the trip.

Such rotating spaceship combinations have been suggested before, of
course, but it seems to me that the Starship design is uniquely apt for
this.

The two Starships would be connected by two cables (wire ropes) starting
from the outer ends of the two articulated aft fins and passing through
non-load-bearing connections ("rings", "eyelets") at the outer ends of
the two front fins. The weight (centripetal acceleration) of each
Starship would thus be carried by the outer ends of the aft fins, just
as when the Starship has landed and these fins act as two of the three
landing legs. The connection to the front fins would stabilize the
Starship in a "nose-up" position. Alternatively, a third cable could
connect to the third (dorsal) landing leg for an even closer emulation
of the landed, upright state.

The articulation (rotation) range of the fins seems (from the videos)
large enough to place the pull from the cables close to the center of
gravity of the Starship -- even if the third landing leg is not used --
so the simulated gravity would be aligned with the long axis of the
Starship, as in the landed position.

For a Mars trip, a simulated Martian gravity level could be used, giving
less stress and weaker Coriolis effects than full Earth gravity. The
same two-Starship bolas system could be used in Earth orbit to test the
long-term effects of Martian gravity levels before Mars trips are
undertaken.

There may be a thermal problem. The Starship carries cryopropellants
which must not evaporate away during the trip from Earth to Mars or vice
versa. In the SpaceX trip videos, the Starship points away from the Sun,
and is furthermore shadowed by a semi-circular fan of solar cells
unfolded at the aft end of the Starship. This prevents solar heating of
the Starship structure, which may be important to limit propellant
evaporation. In a rotating Starship pair the same shadowing is not
possible. The illumination conditions depend on the orientation of the
rotation axis.

For human comfort, it seems best for the rotation axis to point at the
Sun, which means that the direction of incoming sunlight and the
position of the Sun as seen from the Starships are constant and not
rotating. (Another nice feature of this orientation is that the
Starships could be slowly rolled around their long axes to simulate a
day-night cycle.) However, this also means that both Starships are
constantly illuminated and heated from one side, which may cause
propellant evaporation.

If the rotation axis is perpendicular to the Sun direction, the average
solar illumination of the Starships is reduced, but is still larger than
in the fixed away-from-Sun attitude. As seen from a Starship the Sun
rotates around the Starship, front to aft and back again, once per
Starship rotation. This rapid rotation of the illumination may be very
distracting to the passengers.

A lesser problem may be how to mount the solar cell fans. Their original
aft-facing position at the aft Starship end is now bad, because the fans
would not be well illuminated and would be stressed by centripetal
forces. One solution is to mount the solar cell fans on the cables, at
the center of rotation. If the rotation axis does not point at the Sun,
or if the centripetal forces are still too strong even this close to the
axis, the fans could be decoupled from the rotation by a rotating
electrical coupling at the rotation axis.

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

--
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
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  #2  
Old May 25th 19, 01:58 PM posted to sci.space.policy
David Spain
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Posts: 2,565
Default Two Starships in "bolas" rotation

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. 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. 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.

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. 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.

We are along a familiar trajectory here. Same one as was taken for
recoverable Falcon 9 stages. 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.
However the first part of that curve is the hardest. Or would appear so
from where we stand today. 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.

Your bolas configuration could be tried out in LEO. If such a plan were
part of a SpaceX requirement this would make a lot of sense. 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.

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. At least until we get to
Mars. I put the word fine in quotes because there are going to be
physiological effects. The key question is whether we define those
effects as debilitating. Some might consider the inability to return to
Earth as disabling. Others might not. Same with Mars. The key in all
cases is whether medically humans can adapt to a sudden change in 'g'
long term. Is life in space like smoking? If you are guaranteed to die
after 15 years in lunar surface conditions, will that be a deterrent? Or
would the experience of a (short) life in space on the moon be worth
every otherwise lost year? Let's hope we're not forced into that kind of
choice, but right now there is no reason to say it can't happen. We need
more data.

Dave
  #3  
Old May 26th 19, 01:16 PM posted to sci.space.policy
Jeff Findley[_6_]
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Posts: 1,973
Default Two Starships in "bolas" rotation

In article , says...

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. 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. 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.


This is all still very notional since Starship/Super Heavy has yet to
fly. But I do believe the plan was always for Starships to make the
journey to Mars in pairs. That would provide redundancy. Tankers are a
separate thing which are obviously needed in order to top off the
propellant tanks of Starship.

And to do this "right", IMHO, you need even more Starships. What you'd
want to do is to preposition a return Starship (or at least a propellant
production Starship which would stay on Mars) which would produce
propellant for the return trip. Once that's "full", you'd send your
crewed ship. Otherwise, there's no coming back if the crewed Starship
fails to make its own propellant once on Mars.

The only way the delta-V case for crewed Mars missions is by using in
situ propellant production.

But frankly I think Mars is a long way off. In fact the Moon is
becoming a major distraction.


Agreed.


And that actually makes sense since all this
hardware can be tested out far more easily on lunar missions.


Disagree. The hardware will be very different between the two. For
starters, the landing mode is different. Mars has a thin atmosphere
which you want to use to shed as much delta-V as possible. The moon
lacks any atmosphere. This also means that in situ propellant
production will be completely different. On Mars it will rely on CO2
from the atmosphere. On the moon, it would rely on any water which can
be produced from local resources. This means different fuels will be
produced (methane on Mars, LH2 on the moon). So even the engines will
need to be different. In fact, the difference in atmospheres drives a
lot of the engineering, so the hardware just won't be the same at all.

Second, power generation challenges are different. The long lunar night
makes for a large electricity storage requirement. Mars night is much
shorter. Mars dust storms provide a challenge for solar arrays. The
moon has no dust storms, but does have dust which can be kicked up by
human and robotic activity and then stick to surfaces via static
electric forces.

Third, spacesuits are likely to be quite different. The 1/6 gravity of
the moon allows for much more massive designs than Mars suits. This is
a huge challenge when designing practical Mars suits.

Fourth, dust challenges are different. Both bodies have dust. But the
dust is hugely different. On Mars you have dust storms and the dust can
have perclorates in it which make it toxic, so it has to be dealt with
in order to prevent humans from coming into contact with it. On the
moon, the dust has super sharp edges due to no weathering and it is
famously abrasive. It's primary health hazard would be the lungs, which
don't tolerate small particles of any origins. But lunar dust is
largely non-toxic in other respects. So even though "dust bad", the
solutions for dealing with that dust might end up being different due to
the different properties of that dust.

I'm sure I could go on, but I think I've made my point.


If you want to go to Mars, go to Mars. Going to the moon first is
largely a distraction because most of that "experience" gained will be
thrown out and nearly everything will need to be re-engineered
specifically for the Martian surface environment.

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.


Clearly, especially since the current NASA plan of record doesn't
include Starship in any meaningful way. It still relies heavily on
SLS/Orion, so we will be limited to one crewed mission per year. That's
pretty weak sauce considering how "close" the moon is.



We are along a familiar trajectory here. Same one as was taken for
recoverable Falcon 9 stages. I think Starship will focus on P2P
suborbital trajectories first to establish launch and return procedures
that must work anyway.


Only if they can find a paying customer. Such flights without Super
Booster would be severely limited in P2P range. All P2P promotional
videos made to date show Starship being lofted by Super Booster. I
personally think we'll see Starship only flights for testing, but
nothing else.

Then a push to orbit, then a push beyond.


I personally think the "push beyond" will take a very long time. Once
Starship/Super Booster is flying to earth orbit, its primary mission
will be Starlink satellite deployment. Yes you can keep flying up to 60
Starlink satellites at a time on Falcon 9 (more polar orbits will either
have less satellites or require Falcon Heavy launches), but when the
goal is on the order of 12,000 satellites (by the mid 2020s), that's at
least 200 Falcon/Falcon Heavy launches in a few short years! If we
guess those launches cost on average $50 million each, that's $10
billion in launch costs just to get the initial constellation up and
running!

And keep in mind the lifetime of these satellites is relatively short
(from memory something like 3-5 years), so this isn't a "one time"
thing. If Starlink is successful, SpaceX will be continuously launching
its own Starlink satellites for some time to come.

SpaceX needs Starlink for the potential revenue to attract investors to
develop Starship/Super Heavy. But SpaceX also needs Starship/Super
Heavy to launch and maintain the Starlink constellation.

Mars is still Musk's ultimate goal, but Starlink will need to come first
in order to provide the massive cash flow needed to turn Starship from a
cargo launcher into a true crewed spaceship capable of performing an
actual Mars mission. IMHO, of course.

Opening
out the envelope becomes easier the further along the curve you get.
However the first part of that curve is the hardest.


Each part of the development of Starship will present its own
challenges. But getting it from development to a cargo launcher
involves the same types of challenges that Falcon development had.
They've done this before.

Going from cargo launcher to crewed Mars spacecraft involves a whole
host of other challenges that SpaceX has yet to face. That's where the
true "unknown unknowns" are hiding.

Talking more about the configuration of the two Starships on an actual
flight to Mars is a tad premature, IMHO, so I'm going to snip the rest
of the discussion, interesting as it is.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.
  #4  
Old May 26th 19, 04:45 PM posted to sci.space.policy
Fred J. McCall[_3_]
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Posts: 10,018
Default Two Starships in "bolas" rotation

David Spain wrote on Sat, 25 May 2019 08:58:45
-0400:

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. 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.


The SpaceX plan (which I consider wildly optimistic) is to send two
cargo Starships to Mars in 2022, followed by two more cargo Starships
plus two crewed Starships in 2024. Moon flights before 2022. I think
you need to shift everything 2-4 years to the right to get to
something that removes the "wildly" from "wildly optimistic".


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.


It takes at least 3-4 tanker launches to refuel a single Starship for
a Mars (or a Moon, if you intend to land and return to Earth) trip.


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. 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'm not convinced NASA has its own direction, other than to build some
hardware (like Gateway). They vacillate with whatever the then
current President wants. So we've seen things go from Mars to
Asteroid Retrieval to Moon over the last three Presidents. Musk plans
on Mars, regardless of what NASA does. Blue Origin appears to be Moon
focused.


We are along a familiar trajectory here. Same one as was taken for
recoverable Falcon 9 stages. I think Starship will focus on P2P
suborbital trajectories first to establish launch and return procedures
that must work anyway.


I think pursuit of P2P as a first goal is unlikely. Expect to see
some non-orbital hopper tests, followed by some hopper 'dives' to
validate thermal protection and such. These will all launch and
return in Texas with no Falcon Super Heavy booster involved. From
there the next stop is probably the free return trip around the Moon.


Then a push to orbit, then a push beyond. Opening
out the envelope becomes easier the further along the curve you get.
However the first part of that curve is the hardest. Or would appear so
from where we stand today. 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.


I don't think 'crew' will ever be considered 'essential' just to fly
the vehicle. After all, the Mars plan has the first two ships to Mars
as cargo only. And that's really what you want, since you want your
first trips to do things like set up something to manufacture fuel so
that your later manned flights can refuel to get home.


Your bolas configuration could be tried out in LEO. If such a plan were
part of a SpaceX requirement this would make a lot of sense. 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.


Except such a plan is NOT part of the SpaceX requirements. THEIR plan
is to do transits that are sufficiently fast in a ship that is large
enough to carry along whatever exercise equipment is required.


--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw
  #5  
Old May 26th 19, 04:48 PM posted to sci.space.policy
Niklas Holsti
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Posts: 100
Default Two Starships in "bolas" rotation

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
. @ .
  #6  
Old May 26th 19, 05:32 PM posted to sci.space.policy
Niklas Holsti
external usenet poster
 
Posts: 100
Default Two Starships in "bolas" rotation

On 19-05-26 15:16 , Jeff Findley wrote:
...
Once
Starship/Super Booster is flying to earth orbit, its primary mission
will be Starlink satellite deployment. Yes you can keep flying up to 60
Starlink satellites at a time on Falcon 9 (more polar orbits will either
have less satellites or require Falcon Heavy launches), but when the
goal is on the order of 12,000 satellites (by the mid 2020s), that's at
least 200 Falcon/Falcon Heavy launches in a few short years! If we
guess those launches cost on average $50 million each, that's $10
billion in launch costs just to get the initial constellation up and
running!


According to Wikipedia, $10 billion is indeed the Starlink cost estimate.

Starlink launches would use the "satellite delivery" version of
Starship, right? So that has to be developed. But it seems to me that if
these things are reusable, and rapidly reusable, to the degree that
SpaceX is planning, one or two Super Heavy boosters and one or two
satellite deliverers should be enough to finish building Starlink and
maintaining it.

That is an operational use of Super Heavy and the Starship. If Starlink
proves to work after the minimal number of satellites is up, it seems
likely that SpaceX will be able to finance and run such Starlink
operations in parallel with further development of the crewed Starship
version and the Tanker version.

And keep in mind the lifetime of these satellites is relatively short
(from memory something like 3-5 years), so this isn't a "one time"
thing.


I think that lifetime refers to a failed, dead satellite, in the lower
orbits, yes? AIUI working satellites use ion engines that will extend
their lifetime.

(There are developments in air-breathing ion enginges for very low Earth
orbits that could make the lifetime independent of the launched
propellant mass.)

If Starlink is successful, SpaceX will be continuously launching
its own Starlink satellites for some time to come.


Yes, but if those launches are part of day-to-day Starlink operations,
reusing the same launchers, why should they prevent further development
aiming at Mars?

--
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
. @ .
  #7  
Old May 27th 19, 12:18 AM posted to sci.space.policy
Fred J. McCall[_3_]
external usenet poster
 
Posts: 10,018
Default Two Starships in "bolas" rotation

Niklas Holsti wrote on Sun, 26 May
2019 19:32:54 +0300:

On 19-05-26 15:16 , Jeff Findley wrote:
...
Once
Starship/Super Booster is flying to earth orbit, its primary mission
will be Starlink satellite deployment. Yes you can keep flying up to 60
Starlink satellites at a time on Falcon 9 (more polar orbits will either
have less satellites or require Falcon Heavy launches), but when the
goal is on the order of 12,000 satellites (by the mid 2020s), that's at
least 200 Falcon/Falcon Heavy launches in a few short years! If we
guess those launches cost on average $50 million each, that's $10
billion in launch costs just to get the initial constellation up and
running!


According to Wikipedia, $10 billion is indeed the Starlink cost estimate.


But that $10 billion is not just launch costs, but rather total system
cost from designing the thing to building all the satellites to
deploying them to required ground stations.

And keep in mind the lifetime of these satellites is relatively short
(from memory something like 3-5 years), so this isn't a "one time"
thing.


I think that lifetime refers to a failed, dead satellite, in the lower
orbits, yes? AIUI working satellites use ion engines that will extend
their lifetime.


No. 'Lifetime' generally refers to the operating lifespan of the
satellite, which for these is 5 years or less.

If Starlink is successful, SpaceX will be continuously launching
its own Starlink satellites for some time to come.


Yes, but if those launches are part of day-to-day Starlink operations,
reusing the same launchers, why should they prevent further development
aiming at Mars?


Because it's going to tie up resources like launch pads, launch
management, etc. Once Starlink is complete it takes a Falcon 9 launch
per week just to replace satellites that are falling out of orbit.


--
"Millions for defense, but not one cent for tribute."
-- Charles Pinckney
  #8  
Old May 27th 19, 01:24 AM posted to sci.space.policy
Fred J. McCall[_3_]
external usenet poster
 
Posts: 10,018
Default Two Starships in "bolas" rotation

Jeff Findley wrote on Sun, 26 May 2019
08:16:34 -0400:

In article , says...

And that actually makes sense since all this
hardware can be tested out far more easily on lunar missions.


Disagree. The hardware will be very different between the two.


I agree with Jeff on this one. While some hardware designed for Mars
can be tested on the Moon (or on Earth, for that matter) and might be
useful for lunar landing and settlement, there are lots of
differences.


For
starters, the landing mode is different. Mars has a thin atmosphere
which you want to use to shed as much delta-V as possible. The moon
lacks any atmosphere. This also means that in situ propellant
production will be completely different. On Mars it will rely on CO2
from the atmosphere. On the moon, it would rely on any water which can
be produced from local resources. This means different fuels will be
produced (methane on Mars, LH2 on the moon). So even the engines will
need to be different. In fact, the difference in atmospheres drives a
lot of the engineering, so the hardware just won't be the same at all.


Yep. This is why Blue Origin's Blue Moon lander is an LH2/LOX
vehicle. It's specifically intended for lunar work. Meanwhile,
Starship can also do lunar work but does so by refueling in LEO just
like it would for a Mars mission and then NOT requiring a refueling at
the Moon to take off and get back to Earth.


Second, power generation challenges are different. The long lunar night
makes for a large electricity storage requirement. Mars night is much
shorter. Mars dust storms provide a challenge for solar arrays. The
moon has no dust storms, but does have dust which can be kicked up by
human and robotic activity and then stick to surfaces via static
electric forces.


I don't think anyone is seriously planning on solar for either Moon or
Mars. Blue Origin is planning to use hydrogen fuel cells run by boil
off from the Lander Element LH2 tank so as to get through that two
weeks of frigid night on the Moon. I think Mars settlements are
expected to use small nuclear reactors like KRUSTY. Once on the
surface of either the Moon or Mars I would expect that Starship would
deploy one or more of these for 'shore power'.

snip


If you want to go to Mars, go to Mars. Going to the moon first is
largely a distraction because most of that "experience" gained will be
thrown out and nearly everything will need to be re-engineered
specifically for the Martian surface environment.


I want to go to both and I think Starship is the only feasible system
being talked about that can do that. After all, ships that return
from Mars need SOMETHING to do until the next conjunction.

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.


Clearly, especially since the current NASA plan of record doesn't
include Starship in any meaningful way. It still relies heavily on
SLS/Orion, so we will be limited to one crewed mission per year. That's
pretty weak sauce considering how "close" the moon is.


Starship doesn't fit their desired architecture. Once they admit that
Starship is real, all their plans and hardware go into a cocked hat.
If you think the graphic Musk showed of Starship docked to ISS looked
a little silly, imagine the same thing with the much smaller Gateway.


We are along a familiar trajectory here. Same one as was taken for
recoverable Falcon 9 stages. I think Starship will focus on P2P
suborbital trajectories first to establish launch and return procedures
that must work anyway.


Only if they can find a paying customer. Such flights without Super
Booster would be severely limited in P2P range. All P2P promotional
videos made to date show Starship being lofted by Super Booster. I
personally think we'll see Starship only flights for testing, but
nothing else.


I'm inclined to agree. The big stumbling block for P2P, though, is
having all the facilities on the ground built to support it and
getting through the regulatory hurdles.

Then a push to orbit, then a push beyond.


I personally think the "push beyond" will take a very long time. Once
Starship/Super Booster is flying to earth orbit, its primary mission
will be Starlink satellite deployment. Yes you can keep flying up to 60
Starlink satellites at a time on Falcon 9 (more polar orbits will either
have less satellites or require Falcon Heavy launches), but when the
goal is on the order of 12,000 satellites (by the mid 2020s), that's at
least 200 Falcon/Falcon Heavy launches in a few short years! If we
guess those launches cost on average $50 million each, that's $10
billion in launch costs just to get the initial constellation up and
running!


It takes a Falcon 9 launch every week just to maintain things once
they're up. However, I disagree with you. I think you'll see "push
beyond" in parallel with satellite deployment. Remember, these are
fast turnaround reusable vehicles.


And keep in mind the lifetime of these satellites is relatively short
(from memory something like 3-5 years), so this isn't a "one time"
thing. If Starlink is successful, SpaceX will be continuously launching
its own Starlink satellites for some time to come.


Yep. They're going to have to replace something like 2500 satellites
a year once the full system is up.


SpaceX needs Starlink for the potential revenue to attract investors to
develop Starship/Super Heavy. But SpaceX also needs Starship/Super
Heavy to launch and maintain the Starlink constellation.


You're starting to make this sound like trying to fly by tugging on
your own bootstraps. SpaceX has gotten over a billion in investment
and it is ALL going to StarLink (and none to Starship/Falcon Super
Heavy).


Mars is still Musk's ultimate goal, but Starlink will need to come first
in order to provide the massive cash flow needed to turn Starship from a
cargo launcher into a true crewed spaceship capable of performing an
actual Mars mission. IMHO, of course.


While I think Musk is overly optimistic (as usual), I think you are
overly pessimistic. I'd bet on a manned Mars mission before 2030 with
the potential for lunar missions before that.


--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw
  #9  
Old May 27th 19, 07:33 AM posted to sci.space.policy
Fred J. McCall[_3_]
external usenet poster
 
Posts: 10,018
Default Two Starships in "bolas" rotation

JF Mezei wrote on Sun, 26 May 2019
23:10:24 -0400:

On 2019-05-26 20:24, Fred J. McCall wrote:

your own bootstraps. SpaceX has gotten over a billion in investment
and it is ALL going to StarLink (and none to Starship/Falcon Super
Heavy).


SO now, you agree there are investors for the BFR/BFS project?


Do you not read ****ing English? Which part of "it is ALL going to
StarLink" is it that you think says it is going to Starship/Falcon
Super Heavy?


You
blasted me in the not distant past for saying investors in BFR/BFS
expect to see return on investment and want a realistic project that
doesn't constantly change.


Yes, and I'm blasting you now for not being able to read simple
declarative English sentences. Which part of "none to Starship/Falcon
Super Heavy" is it that you think indicates some is going to
Starship/Falcon Super Heavy?


--
"Ignorance is preferable to error, and he is less remote from the
truth who believes nothing than he who believes what is wrong."
-- Thomas Jefferson
  #10  
Old May 27th 19, 08:28 AM posted to sci.space.policy
William Elliot[_4_]
external usenet poster
 
Posts: 75
Default Two Starships in "bolas" rotation

On Sun, 26 May 2019, Fred J. McCall wrote:
Jeff Findley wrote on Sun, 26 May 2019
And keep in mind the lifetime of these satellites is relatively
short (from memory something like 3-5 years), so this isn't a "one
time" thing. If Starlink is successful, SpaceX will be
continuously launching its own Starlink satellites for some time to
come.


Yep. They're going to have to replace something like 2500 satellites
a year once the full system is up.


A huge investement that has to constantly tread water? Insanity!
 




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