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#926 2021-02-21 12:01:56

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,254
Website

Re: Starship is Go...

Hi Oldfart1939:

Musk said in his Boca Chica presentation in front of a Starship prototype that they wanted takeoff thrust/weight at about 1.5 in order to achieve the right accelerations and speeds during ascent.  The nominal thrust of a sea level Raptor at 4200 psia chamber pressure is 2 MN.  Actually 1.957,  but who's quibbling?  They have 3 in a prototype,  so that's just a hair under 6 MN thrust available.  At factor 1.5 T/W,  the max weight is then just a hair under 4 MN.   

4 MN Earth weight is a mass of no more than about 399 metric tons at liftoff.  Supposedly there is no payload,  and the inert mass is 120 metric tons.  That's a max propellant load of 279 metric tons to take off and fly with good ascent kinematics.  My best guess is they have been flying with about 100-150 tons so far. 

If you relax the T/W = 1.5 constraint,  you can technically fly with more propellant,  but it won't pick up much speed until a lot of that is burned.  It won't fly as high.   The limit is T/W = 1,  where it just sits on the pad without rising at all,  initially.  That happens at total mass 599 tons,  with 479 tons of propellant.

The tankage capacity in Starship is supposedly 1200 metric tons of propellant,  so these flight tests are inherently very,  very limited in the ultimate altitudes and speeds they can achieve. 

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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#927 2021-02-21 12:02:16

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 5,138

Re: Starship is Go...

For Oldfart1939 re #925

Airliners occasionally circle to burn off excess fuel before landing.

If having to defuel is a problem, and I recognize the less fuel to remove the better, then just hovering for a while should do the trick.

(th)

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#928 2021-02-21 16:47:39

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 21,338

Re: Starship is Go...

Not mention a longer full thrust would aid in telling if shutting them down or the clanging of the bells and the next thought is the cold fuel thermal cycle should be looked at.
Starship SN10’s Raptors installed as testing begins

just as soon as possible sn11 will emerge with its nose to get ready for its flight

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#929 2021-02-21 19:28:45

Oldfart1939
Member
Registered: 2016-11-26
Posts: 1,957

Re: Starship is Go...

tah-

In flying circles, the only time you can have too much fuel onboard is when the aircraft is on fire.

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#930 2021-02-22 12:52:48

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,254
Website

Re: Starship is Go...

I second OF's motion.

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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#931 2021-02-22 13:20:33

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 5,138

Re: Starship is Go...

For Oldfart1939 and GW Johnson (and probably kbd512 if he'd posted to this topic) ...

I call it a good day when I get a chance to learn something ...

The response of experienced pilots to the comment about burning off fuel before landing a Starship surprised me, because it is newsworthy when commercial aircraft dump fuel, and it happens often enough so that I was aware of it, but had not taken the time to learn why such a costly waste of expensive fuel is done.

Google came up with a couple of explanations ... neither of these would seem to me to apply to a private pilot ...

Showing results for why do airplanes dump fuel before landing
Search instead for why do airliners dump fuel before landing
Image result for why do airplanes dump fuel before landing
Some airplanes – usually larger ones – have the capability to dump fuel to reduce the landing weight. Dumping fuel can reduce the weight quickly, dumping thousands of pounds in a few minutes. ... And pilots are trained to climb to a higher altitude, which allows the atomized fuel to evaporate before it reaches the ground.Jan 17, 2020

Ask the Captain: Why do planes dump fuel before emergency ...

and ...

https://www.businessinsider.com/planes- … cy-2019-12

Anthony Brickhouse: Fuel dumping, simply explained, is an aircraft losing weight before it lands.

Narrator: Anthony is an Associate Professor at Embry-Riddle Aeronautical University. And what he's talking about is officially called a fuel jettison. Planes are designed to land below certain weights. A heavier plane is more likely to hit the ground hard and get damaged. It's got 5,000 gallons of fuel, which is about three elephants weighing it down. So, landing with a full tank is pretty risky. But most flights aren't landing with a full tank. They might not be taking off with a full tank either. Before takeoff, the flight planner calculates the amount of fuel needed to complete the trip. So that enough fuel gets burned off over the course of the flight and the plane's weight comes down and then it's safe to land. A pilot will choose to dump fuel only on very rare occasions.

(th)

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#932 2021-02-22 17:47:08

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 21,338

Re: Starship is Go...

The only time is during the glide when throttled back engines can be used but how steerable are the winglets for turns? I thought that they were for pitch....

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#933 2021-02-23 18:15:07

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,975

Re: Starship is Go...

Interesting "state of progress" video from Felix of the What About It channel:

https://www.youtube.com/watch?v=NSa3AWjThwU


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

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#934 2021-02-23 20:43:04

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 21,338

Re: Starship is Go...

EupxbANVkAA61_r-1536x864.jpg

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#935 2021-02-24 08:08:02

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,975

Re: Starship is Go...

An incredible work rate! It's a good job Musk is, officially, the richest person on the planet.

But what the hell is SN72??? Does anyone know?


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

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#936 2021-02-24 08:30:29

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 5,138

Re: Starship is Go...

For Louis #935

First, thanks for the latest link to What About It!  That was another interesting piece by Felix!

Regarding the mysterious #72 ... we may see that number if Elon and his team keep going as they've been.

However, the prototype in question is 7 (point) 2.

(th)

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#937 2021-02-24 08:35:07

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,975

Re: Starship is Go...

Ah! Thanks for the clarification - I couldn't enlarge the image!

tahanson43206 wrote:

For Louis #935

First, thanks for the latest link to What About It!  That was another interesting piece by Felix!

Regarding the mysterious #72 ... we may see that number if Elon and his team keep going as they've been.

However, the prototype in question is 7 (point) 2.

(th)


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

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#938 2021-02-24 10:27:20

Oldfart1939
Member
Registered: 2016-11-26
Posts: 1,957

Re: Starship is Go...

Louis-
I believe that SN 7.2 is constructed from 3 mm thickness stainless steel rather than 4 mm thickness, in a move to save vehicle weight and thereby, increase actual payload capacity of Starship.

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#939 2021-02-24 16:01:33

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,975

Re: Starship is Go...

Thanks for the further clarification...

Oldfart1939 wrote:

Louis-
I believe that SN 7.2 is constructed from 3 mm thickness stainless steel rather than 4 mm thickness, in a move to save vehicle weight and thereby, increase actual payload capacity of Starship.


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

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#940 2021-02-24 17:57:00

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 21,338

Re: Starship is Go...

The mass reduction also benefits the bfr booster as it does not need to be reinforced to support the heavier starship...

https://www.spacex.com/media/starship_u … ide_v1.pdf

Starship SN10 Static Fires, but requires engine swap – Super Heavy waiting in the wings

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#941 2021-02-25 12:56:40

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 21,338

Re: Starship is Go...

Engine tests have happened along with a swap out of units not meeting the grade in preparation of a second engine test and potential launch New SpaceX Starship prototype SN10 rocket could fly as soon as Friday

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#942 2021-02-27 15:28:03

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 21,338

Re: Starship is Go...

Starship SN10 Static Fires twice – Super Heavy waiting in the wingsNSF-2021-02-26-15-08-56-258-1170x729.jpg


Should all go to plan with the latest attempt, SN10 will get to plant her landing legs into a resurfaced and expanded landing pad.

Thanks to the accuracy of the SN8 and SN9 returns, the resulting RUDs (Rapid Unscheduled Disassemblies) have caused some damage to the pad requiring repairs. Ahead of SN10, the entire pad was expanded and laid with rebar before being surfaced with fresh concrete on Sunday. How long that concrete takes to cure was the subject of social media speculation and may ultimately be the deciding factor when SN10 launches.

Conrete laying video

Well that answers the need for a mars pad to be made....

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#943 2021-02-28 06:54:55

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,975

Re: Starship is Go...

I am so much more excited about the Starship programme than the Perseverance Rover!


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

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#944 2021-03-02 20:04:56

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,975

Re: Starship is Go...

Latest helpful update from Felix (WAI):

https://www.youtube.com/watch?v=ENJ0UocwrqI


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

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#945 2021-03-03 11:18:01

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,975

Re: Starship is Go...

Felix (WAI site) has a Live Stream on the SN10 launch which will happen soon we hope.

https://www.youtube.com/watch?v=xR1wv0iUKSU


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

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#946 2021-03-03 14:19:46

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,975

Re: Starship is Go...

Abort! sad  sad  sad


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

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#947 2021-03-03 14:21:36

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,975

Re: Starship is Go...

At 0 seconds! First time I've ever seen that. A testament to modern computing power I guess!


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

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#948 2021-03-03 18:14:01

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 5,138

Re: Starship is Go...

For Louis re updates .... thanks for posting the link to the real-time report!  I was in the audience when the hold went into effect.  I was willing to forgo other activities if the launch had proceeded.  At least ** this ** way, the vehicle is still there, intact, available for another try!

(th)

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#949 2021-03-03 18:38:27

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,975

Re: Starship is Go...

I was misled by the Space X commentator into thinking they had abandoned the launch attempt for the rest of today but no - they tried again and succeeded!

Amazing achievement. 10 Km flight and faultless landing.

Obviously I'm not a rocket scientist but I think they've accomplished already the three most difficult parts of an orbital flight - the launch, the flip and the landing.

So I guess the booster is the next critical stage...?

Anyway, Space X have once again shown themselves to be true pioneers. Orbital flight this year looks very possible if bureaucratic interference can be avoided.

2021 Non human Starship to orbit

2022 Human Starship to orbit

2022-2023 Lunar circumnavigation and possible lunar surface landing with humans together with Starship test landings on Mars analogue rock slabs or on rock fields on Earth. 

2023 - 2025  Testing of all Mars human mission systems e.g. hab unloading and erection, use of Rovers, life support systems,  drilling for water ice, methane production, coms etc etc.

2024 - Mars cargo landings 

2026 Humans to Mars


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

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#950 2021-03-03 18:51:23

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,975

Re: Starship is Go...

JUst catching up with things...it subsquently exploded/imploded after a pretty good if slightly bumpy landing.


louis wrote:

I was misled by the Space X commentator into thinking they had abandoned the launch attempt for the rest of today but no - they tried again and succeeded!

Amazing achievement. 10 Km flight and faultless landing.

Obviously I'm not a rocket scientist but I think they've accomplished already the three most difficult parts of an orbital flight - the launch, the flip and the landing.

So I guess the booster is the next critical stage...?

Anyway, Space X have once again shown themselves to be true pioneers. Orbital flight this year looks very possible if bureaucratic interference can be avoided.

2021 Non human Starship to orbit

2022 Human Starship to orbit

2022-2023 Lunar circumnavigation and possible lunar surface landing with humans together with Starship test landings on Mars analogue rock slabs or on rock fields on Earth. 

2023 - 2025  Testing of all Mars human mission systems e.g. hab unloading and erection, use of Rovers, life support systems,  drilling for water ice, methane production, coms etc etc.

2024 - Mars cargo landings 

2026 Humans to Mars


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

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