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#126 2019-01-24 15:34:49

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 3,565
Website

Re: Starship is Go...

Knowing to worry about many such things is a result of advanced age and lots of relevant experience.  Youngsters out of school may be talented computer software operators,  but they don't have the experience to know what to really worry about. 

Myself,  if the machines fail,  I still have pencil and paper and my slide rule.  I'm not crippled,  just slowed down a bit.  I know what to worry about. And how to figure it,  too.

GW

Last edited by GW Johnson (2019-01-24 15:35:46)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#127 2019-01-24 17:59:41

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 15,818

Re: Starship is Go...

We just talked about how the winds are stronger with hieght so the taller the rocket is the more sever its going to be when fuel tanks are empty. Then add to that 150 tons of payload at the top and its not standing for long......

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#128 2019-01-24 20:03:17

Void
Member
Registered: 2011-12-29
Posts: 3,011

Re: Starship is Go...

I would say that this event is a blessing.  My understanding if correct is that the propellant tanks were not involved.

And indeed, if they had not had this warning it could have been a real starship.  That would have been a letdown.

Kids fall down, then they get up we hope, and do better.

Done.

Last edited by Void (2019-01-24 20:28:38)


I like people who criticize angels dancing on a pinhead.  I also like it when angels dance on my pinhead.

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#129 2019-01-24 22:05:06

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 15,818

Re: Starship is Go...

https://www.universetoday.com/141328/sp … igh-winds/

Screen-Shot-2019-01-23-at-10.35.14-AM.jpg

4 to 8 weeks to make repairs if all goes well

~1750K is peak heating expected on about 20% of Starship for LEO entry, ~1600K on 20%. Rest drops below 1450K, so no heat shield needed. Radiative cooling at T^4 takes care of 60% of the ship.

A dragon hits higher temperatures for the same location for return to earth and it has a heatshield....

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#130 2019-01-25 11:43:43

louis
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From: UK
Registered: 2008-03-24
Posts: 4,706

Re: Starship is Go...

Interesting video from Scott Manley

https://www.youtube.com/watch?v=GfWarGb_hds

He explains how austenitic (?) steel becomes stronger at v. low temperatures. And how Space X plan to use liquid methane forced through the porous steel to create a thermally protective layer on re-entry.


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

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#131 2019-01-25 12:08:32

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 3,565
Website

Re: Starship is Go...

1450 K is 2150 F,  too high even for SS 309/310 not to seriously surface scale.  They don't melt,  but have essentially zero strength at such temperatures.  The steel MUST be cooled massively to about 1200 F = 920 K in order to have some strength. 

We'll see if a bare metal design can be done,  I suppose.  My sense of prior work is the massflow of coolant for film cooling is quite large.  Infeasibly-large,  actually.

At Earth entry interface,  speed is about 8 km/s.  A rough estimate of the driving temperature for heat transfer rates would be 8000 K.  The only saving grace is near-zero density at 300 kft ~ 90 km. Halfway down is roughly peak heating and deceleration:  about 4 km/s at about 40-50 km.  The driving temperature is about 4000 K,  and the density is NOT zero,  being about 0.15% of sea level density,  and about 5 times lower than surface density on Mars.

I'd be surprised and pleased if they can hold a metal surface to ~900-1000 K in the face of 4000 K driving temperatures,  with film transpiration cooling.  Nobody else was ever successful doing that;  everybody else uses a heat shield. 

GW

Last edited by GW Johnson (2019-01-25 12:10:16)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#132 2019-01-25 14:13:49

Oldfart1939
Member
Registered: 2016-11-26
Posts: 1,646

Re: Starship is Go...

In case of Starhopper--Elon should have watched "The Martian," again! (He says, tongue in  cheek). smile

Last edited by Oldfart1939 (2019-01-25 14:14:14)

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#133 2019-01-25 14:21:17

elderflower
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Registered: 2016-06-19
Posts: 1,096

Re: Starship is Go...

If you were running a thruster as you reenter you would be plunging into an exhaust plume rather than directly into the plasma. This would reduce the temperature of gas next to the vehicle skin. Adding to that the temperature reduction from cooling and transpiration makes regular stainless looks like a possible material. Its a lot cheaper than Nimonic!

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#134 2019-01-25 19:28:17

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 15,818

Re: Starship is Go...

Nose first is how the ship is entering which is why its got one side in the drawings in darker color. Once it gets to the skip layer where it will tend to lift the nose so the tail dips it will be set so that it can fire the engines for the retropropulsive landing on its tail fin feet..

th?id=OIP.-8rd9BgG8F4W1cmUcyULlAHaEK&w=164&h=100&c=8&rs=1&qlt=90&pid=3.1&rm=2

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#135 2019-01-27 08:08:42

louis
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From: UK
Registered: 2008-03-24
Posts: 4,706

Re: Starship is Go...

You can't see much but it is a live view! smile


https://www.youtube.com/watch?v=L7zia2HqOOc

And here's a nice animation of the Star Hopper.

https://www.youtube.com/watch?v=j7iH9G-araI

Last edited by louis (2019-01-27 12:07:20)


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

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#136 2019-01-27 13:03:21

Void
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Registered: 2011-12-29
Posts: 3,011

Re: Starship is Go...

If you really think about it, I can't find that much fault with SpaceX on the damage to part of the hopper.

It was built after all to find out what the problems were.

And it was criticized because parts of it were built by a water tower company, but why should they spend more money on a test device than they have to?

And it is actually fortunate that that wind was able to tip things over.  That was and should be the purpose of the hopper.  To find out what can go wrong.

Done.


I like people who criticize angels dancing on a pinhead.  I also like it when angels dance on my pinhead.

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#137 2019-01-27 17:02:19

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 15,818

Re: Starship is Go...

I quite agree that prototypes are just for that purpose to wring out the bugs to a design and sometimes to make improvements from what we learn.
This was something I learned from electronic design builds in the R&D labs which takes me back a few decades....

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#138 2019-01-27 19:56:49

louis
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From: UK
Registered: 2008-03-24
Posts: 4,706

Re: Starship is Go...

I love the live cam - see post 135.


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

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#139 2019-01-28 19:02:21

louis
Member
From: UK
Registered: 2008-03-24
Posts: 4,706

Re: Starship is Go...

A new video from Cloudlicker...


https://www.youtube.com/watch?v=Wgnw-idx4vw

Quite a lot about the lego model he's made with his brother but at 4.19 he has a clip from Elon Musk showing testing of the Starship heat shield. I hadn't seen that before.


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

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#140 2019-02-01 22:02:21

Void
Member
Registered: 2011-12-29
Posts: 3,011

Re: Starship is Go...

It seems that the Moon gets bigger.
https://futurism.com/elon-musk-reach-mo … ip-raptor/
https://arstechnica.com/science/2019/02 … sts-first/
These articles appear to suggest that a lesser BFR (SuperHeavy/StarShip) will precede the Mars version.  Hopefully I do understand what is indicated in the articles.  Later better engine capabilities, and I presume a better tested SpaceX capability in general.  Better chances of winning big when it does make the Mars attempt.

And I am very comfortable with that.  I think it is wise, and more likely to get humans to Mars in the long run.
To me it fits better with NASA, and the activities of other companies, such as Blue Origins, and getting paying jobs for Starship.

Done.

Last edited by Void (2019-02-01 22:03:39)


I like people who criticize angels dancing on a pinhead.  I also like it when angels dance on my pinhead.

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#141 2019-02-02 10:26:00

Oldfart1939
Member
Registered: 2016-11-26
Posts: 1,646

Re: Starship is Go...

About 2 yeas ago, I was still advocating a somewhat smaller approach than SpaceX had announced for the then Interplanetary Transport Vehicle, a.k.a. BFR. There was an earlier SpaceX vehicle called Falcon X. It appears to me that Elon is steadily shrinking the BFR to something akin to the smaller vehicle, although still retaining a larger diameter of 9 meters. Maybe BFR was just too big a bite to afford, much less chew? I applaud the "reality check" approach.

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#142 2019-02-02 17:49:42

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 15,818

Re: Starship is Go...

Aside from the glossy images in the articals there is not much math in either of them which is odd for one that indicates its an analysis of the BFR starship with note really anything other than the isp specs for the Raptor engine...

To that end the SLS brute force rocket that is not recycled or recovered is really a let down for its huge cost.

Nasa would have been better off to have given the prints to all the parts and made way for a third party to build from those key pieces....

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#143 2019-02-03 14:37:06

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 3,565
Website

Re: Starship is Go...

If you look at what is on Spacex’s official website instead of other people’s blogs,  and all that social media noise,  you see what Spacex is really probably thinking for what was BFR/BFS,  and is now “Starship”.  I am very distrustful of internet sources,  and especially social media sources.  And with good reason! 

Go to the “making life interplanetary” tab.  There is a lot there,  much of it either revised or new.  The main long video is still the IAC presentation from 2017,  with the illustrations still what was the 12 m dia 2016 version of BFS with two modest delta wings.  Much of the rest of the information depicts the newer 9 m dia 2018 version,  with the 3 fins (2 that fold). 

I saw NOTHING posted there about using transpiration cooling of a metal surface for entry,  either at Mars or Earth!  I did see the 3-fin 9 m dia BFS revised to show ~1 m dia landing pads at the tips of the fins,  something not there a few months ago!  This still shows 7 Raptor engines (3 surrounded by 4),  vacuum or sea level NOT specified,  and a black belly and white leeward side.  That last plus the verbiage about “leveraging Dragon heat shield technology” says the BFS is still a PICA-X-covered entry airframe. 

All the talk about stainless steel may or may not be pointless,  but I think it misses what they are really up to.  The new “grasshopper” vehicle may be stainless for convenience,  but it never sees any aeroheating at all.  It will not fly anywhere supersonic.  They may,  or may not,  have given up on carbon fiber tanks in favor of stainless tanks in the BFS,  I dunno.  That just wasn’t clear.  You could glue PICA-X to either. 

If there’s any transpiration going on (and the site does NOT mention it !!!),  it may really be to handle the thermal wave soaking through the heat shield.  The entry sequence for Mars is 478 sec long!  They may not be able to heat-sink their way through a PICA-X heat shield heating transient that long,  given the thin-wall structures they are showing. 

If the fully-fueled BFS second-stage vehicle still masses something in the 1000-1100 metric ton range at launch,  then its launch weight is near 9.8E6-10.8E6 Newtons on Earth,  and 3.8E6-4.1E6 Newtons on Mars.  If those 3 landing pads really are 1 m dia,  there’s about 2.4 sq.m worth of landing pad area to support those loaded,  ready-to-launch weights. 

On Earth,  that’s about 4.2E6 N/sq.m = 4.2 MPa surface bearing pressure.  That’s 41 atm or some 87,000 lb/sq.ft or about 43 US (short) tons per sq.ft.  Guys,  for all practical purposes,  that’s reinforced concrete only!  And that’s just the static loading at launch.  Double-or-more those soil bearing strengths for any dynamic processes.  Such as the initial jet blast force upon ignition.

On Mars,  those pressures are 1.6 MPa = 16 atm = 34,000 lb/sq.ft = 16.8 US tons/sq.ft.  Hardpan rock-and-sand removable by picking will NOT support this vehicle for launch on Mars,  only solid rock or reinforced concrete will do.  Loose sand and rock (most of Mars) is “right out”,  as they say. 

They’re just going to need a lot more landing pad area to make this thing into a rough-field,  unprepared-ground lander.  That’s just physics and strength of materials talking!  A lot more pad area,  by around a factor of 10 or more!  It is quite obvious to me they are nowhere-near-done designing a practical ship capable of landing anywhere on Mars (or the moon,  which is all loose sand-like regolith).  They still have some very serious fundamentals to think their way through! 

You could get very high landing pad area without a drag penalty on ascent,  or a disruption of entry aerodynamics,  by fitting the fins with hydraulic-opening hinged panels (like landing gear doors).  These fold out to the sides along the touchdown edge,  to form a really big pad surface.  But this is inherently heavy:  this is NOT something you do with thin sheet metal or vulnerable carbon fiber panels.  Rough field operability simply has a high cost,  that I fear Spacex has yet to face.   

I also took a close look at their landing sequence simulation for Mars.  It very clearly shows the ship decelerating through Mach 3 at about 5 km altitude,  which is EXACTLY what I have been saying about high ballistic coefficient entries on Mars,  for some years now.  Surprise,  surprise!  YOU JUST CANNOT ARGUE with physics!

They have to do a lifting pull-up to about 10 km and transonic speeds,  to set up for the final propulsive touchdown.  Almost a full tailslide maneuver.  I worry they may need thrust to augment the body lift for that pull-up.  The “air” there is awfully thin. 

The Earth entry landing sequence isn’t up there on the Spacex site right now.  It was,  a few months ago.  That was the long belly-flop to subsonic speed (after decelerating to Mach 3 at about 40-45 km),  followed by pitching tail-first for the propulsive touchdown. 

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#144 2019-02-03 16:36:55

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 15,818

Re: Starship is Go...

Just opened my eyes and saw that my post was in the wrong topic

SpaceNut wrote:

Here is the lunar path:

SpaceX_MoonOrbit_BFR.png

https://www.spacex.com/sites/spacex/fil … y-2017.pdf

As GW meantioned for Mars the Heatshield is reused a couple of times for hops on mars...

Starship will enter the Mars atmosphere at 7.5 kilometers per second and decelerate aerodynamically. The vehicle’s heat shield is designed to withstand multiple entries, but given that the vehicle is coming into the Mars atmosphere so hot, we still expect to see some ablation of the heat shield (similar to wear and tear on a brake pad).

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#145 2019-02-04 13:28:47

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 3,565
Website

Re: Starship is Go...

I just took an approximate look at the Spacex BFS/Starship landing pad area required for rough-field capability on the moon,  Mars,  and Earth.  The only way to achieve this,  is with the folding-panel idea mentioned in post 143 above.  The required total landing pad surface areas fall in the 30-45 square meter class,  not the 2.5 to 3-something sq.m that Spacex currently shows in its illustrations. 

Such large pad areas will have to fold out of the way.  There is no way around that larger,  folding landing pad requirement,  if rough field capability on Mars and the moon (not to mention Earth) is desired.  Otherwise you are restricted to reinforced concrete (or solid rock) aprons many feet thick. 

See the posting "Designing Rough Field Capability Into the Spacex Starship",  posted 2-4-19,  on my "exrocketman" site.  For those who don't know,  that site is http://exrocketman.blogspot.com.

What I found is that handling what the bulk of Mars's surface seems to be like,  is the critical design condition.  What works for that is more-than-good for the moon,  and for Earth,  despite the variance in surfaces and properties and gravity. It's complicated,  surprise,  surprise!  So what isn't?

GW

Last edited by GW Johnson (2019-02-04 13:30:27)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#146 2019-02-04 13:42:32

Void
Member
Registered: 2011-12-29
Posts: 3,011

Re: Starship is Go...

Alright GW, since no one else is stupid enough to challenge, you, I will at least post, but not dispute the limits you have set.

I don't expect to say anything amazing either.

-For the lunar fly around notion, the landing problems are on Earth only.

-We don't know for sure that SpaceX ever intends to land on the Moon, but I am expecting that eventually they will.  With the Starship itself, or might they partner with Blue Origins Blue Moon?  Or would they develop a lander of their own from items they already have?
I absolutely have no idea what they think.  They might not either at this point.

-I had previously thought that for Moon landings (And not Mars), a pedestal/freight pallet could be attached to the ships base out of the way of points which will be roasted during re-entry.  The reasons are to provide a wide base for the load, and also in my thinking, in LEO perhaps, some of the awkward items could be moved from the internal cargo bays to the landing pedestal/pallet.  To reduce the top heavy nature of the landing device, and to make it easier to offload the awkward items.  But of course this then changes things where you have to bother to get a pedestal structure to LEO, and have to then mate it to that additional structure.  Then I guess that structure could be left behind on the Moon as a landing pad, or taken back up to be re-used from LEO again.  (Not necessarily the way that the Starship itself would return to Earth).

-But really is there a chance that the cargo compartment which is said to be around the engines, could on occasion contain a device to unfold as the ship descends after burn in, and so add landing "Feet" area to the fins of the ship.  Perhaps slide under the fins.

That would take up cargo mass, so I suppose that after the initial 6 ships landed, 4 cargo and 2 crewed, that method would be abandoned as there should have been constructed permanent landing pads on Mars.

Possibilities.  Surely SpaceX has a plan.  I am inclined to believe that they are just not showing their cards yet.

Done.

Last edited by Void (2019-02-04 14:04:01)


I like people who criticize angels dancing on a pinhead.  I also like it when angels dance on my pinhead.

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#147 2019-02-04 14:20:55

kbd512
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Registered: 2015-01-02
Posts: 2,887

Re: Starship is Go...

Instead of folding hydraulically actuated landing pads, why not just attach load bearing stabilization plates when Starship is on the ground prior to refueling operations?

It's still GW's concept, just not with the complication or stowage issues of the hydraulic fold-out mechanism.  The plates can be affixed to the aft cargo area and then attached after landing.  If anything, the landing gear track needs to be wider to prevent the thing from tipping over.

When Starship lands on Earth, it's gonna land on a steel reinforced concrete apron or a steel floating platform.  The only reason to even attempt a rough field landing is that there's no other choice in the matter.

Nevermind, I see that Void already had the same idea.

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#148 2019-02-04 17:45:27

Void
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Registered: 2011-12-29
Posts: 3,011

Re: Starship is Go...

Posts #146 & #147 (By KBD512), may have been missed by any reader.

Here I am posting some "Here Say" in the internet news primarily about BFR & Raptor engines.
Take it for what it is worth.  Where are you Louis?

About it:
https://www.bing.com/videos/search?q=El … ORM=VDQVAP

About it:
https://www.bing.com/videos/search?q=El … tarship%AP

Firing the Raptor Engine:
http://fortune.com/2019/02/04/spacex-rocket-elon-musk/

Oops! I am supposed to make a comment.  Eat at Joes!

Or, the raptor will be a compromise according to the above "Here Say".  Therefore the BFR(Super Heavy/Starship) will be sub optimal at first per capabilities.
Done Done Done Done

Last edited by Void (2019-02-04 17:48:52)


I like people who criticize angels dancing on a pinhead.  I also like it when angels dance on my pinhead.

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#149 2019-02-04 17:50:51

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 15,818

Re: Starship is Go...

Load bearing plates are extension of the pads and need to be in place before its makes ground contact.

The typical landing site for mars seems to be anything but Basalt, granite or other very hard surface materials.

1FK9GOO.jpg

pAL8quI.jpg

all layer cake type rocks which are soft with silt and sand in between them.

The rover is just under 1mT for mass so what would you think will happen when the tonnage 150 mT payload + 100 mT ship combined.

Lm4BARZ.jpg

See the split rock from the mass of the rover

cTsHMGa.jpg

"Working from the rocks' mineral abundances as determined by the Chemistry and Mineralogy instrument, we estimated a grain density of 2,810 kilograms per cubic meter," he said. "However the bulk density that came out of our study is a lot less - 1,680 kilograms per cubic meter."

The much lower figure shows that the rocks have a reduced density most likely resulting from the rocks being more porous. This means the rocks have been compressed less than scientists have thought.

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#150 2019-02-04 18:24:05

louis
Member
From: UK
Registered: 2008-03-24
Posts: 4,706

Re: Starship is Go...

Thanks Void!

Looking good. 

So far only the one major setback - the embarrassing blow-me-down of the upper level of the Star Hopper. Otherwise, things seem to be progressing nicely.

I think maybe Engineering Today are overstating the lunar thing.   In some ways operating on the Moon will be more difficult than operating on Mars (14 day/night cycles for instance). Lunar orbital tourism may become a paying proposition before the Mars landing.

I still can't imagine that Space X are avoiding sponsorship. I think we are seeing rising interest in the Mars project. Someone said on the radio recently that "Elon Musk seems to be everywhere". I think if Space X can get to that credible stage of (a) handling human flight and (b) getting a fully operational Starship prototype into orbit, we might see that surge of interest in Mars that will be the platform for huge sponsorship deals.  They need to think in terms of building up over a few test missions.


Void wrote:

Posts #146 & #147 (By KBD512), may have been missed by any reader.

Here I am posting some "Here Say" in the internet news primarily about BFR & Raptor engines.
Take it for what it is worth.  Where are you Louis?

About it:
https://www.bing.com/videos/search?q=El … ORM=VDQVAP

About it:
https://www.bing.com/videos/search?q=El … tarship%AP

Firing the Raptor Engine:
http://fortune.com/2019/02/04/spacex-rocket-elon-musk/

Oops! I am supposed to make a comment.  Eat at Joes!

Or, the raptor will be a compromise according to the above "Here Say".  Therefore the BFR(Super Heavy/Starship) will be sub optimal at first per capabilities.
Done Done Done Done

Last edited by louis (2019-02-04 18:25:26)


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

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