Spaceship and Rocket Design - Page 12 - SkyscraperCity
 

forums map | news magazine | posting guidelines

Go Back   SkyscraperCity > Fun Forums > Space, Science & Technology

Space, Science & Technology shaping tomorrow's world


Global Announcement

As a general reminder, please respect others and respect copyrights. Go here to familiarize yourself with our posting policy.


Reply

 
Thread Tools
Old January 21st, 2019, 03:52 PM   #221
AcesHigh
Taking On The World
 
AcesHigh's Avatar
 
Join Date: Feb 2003
Location: Novo Hamburgo
Posts: 26,281
Likes (Received): 8597

The rail launch makes almost no difference in the deltaV needed for orbit.

You still need a delta V of 29 thousand km/h.

And you must achieve that delta-V with a vehicle with absolutely the wrong aerodynamics for such high speeds.
__________________
http://gremioemfoco.info/ forum do grêmio, para quem não consegue se conter e falar somente do estádio, uma boa opção
AcesHigh no está en línea   Reply With Quote
Sponsored Links
Advertisement
 
Old January 21st, 2019, 05:17 PM   #222
Kyll.Ing.
Registered User
 
Kyll.Ing.'s Avatar
 
Join Date: Nov 2012
Location: Trondheim
Posts: 1,780
Likes (Received): 5743

Quote:
Originally Posted by AcesHigh View Post
The rail launch makes almost no difference in the deltaV needed for orbit.

You still need a delta V of 29 thousand km/h.

And you must achieve that delta-V with a vehicle with absolutely the wrong aerodynamics for such high speeds.
Agreed on the third point (and also, why bother to lug those huge wings around, any benefit they could feasibly give in the aerodynamic regimes of the flight would be more than cancelled by all the extra weight the rockets have to push around later - even the space shuttle had way too large wings for most of its intended purposes), but the two first are sort of addressed. A spacecraft expends a significant fraction of its fuel (more than a third, according to the quoted Wikipedia paragraph) to achieve 1600 km/h from a standstill. If you could give the same spacecraft that speed without using any fuel, you could cut a third of the fuel volume, and thus save some mass by shrinking the fuel tanks accordingly, giving you even more mileage out of the remaining fuel.

A rail launch system would replace the first rocket stage, which tends to be the largest and most unwieldy one. The first stage of the Saturn V weighed almost four times much as the rest of the rocket put together on takeoff, and it was only used to accelerate it up to 2300 m/s. Increasing delta-v is more expensive the more you have, and even going from 30k km/s to 29 would be a huge saving in take-off mass.

That being said, given the complexity of a rail launch system, I guess it would be far simpler to just use that rocket stage in most cases. It could even be recovered and reused, making it pretty cost-effective per launch. Building such rails aren't cheap, and maintaining them isn't either. A rocket is probably competitive and then some.
Kyll.Ing. no está en línea   Reply With Quote
Old January 21st, 2019, 05:59 PM   #223
fountainkopf
Registered User
 
fountainkopf's Avatar
 
Join Date: Aug 2013
Location: Endor
Posts: 750
Likes (Received): 179

Quote:
Originally Posted by Kyll.Ing. View Post
Agreed on the third point (and also, why bother to lug those huge wings around, any benefit they could feasibly give in the aerodynamic regimes of the flight would be more than cancelled by all the extra weight the rockets have to push around later - even the space shuttle had way too large wings for most of its intended purposes), but the two first are sort of addressed. A spacecraft expends a significant fraction of its fuel (more than a third, according to the quoted Wikipedia paragraph) to achieve 1600 km/h from a standstill. If you could give the same spacecraft that speed without using any fuel, you could cut a third of the fuel volume, and thus save some mass by shrinking the fuel tanks accordingly, giving you even more mileage out of the remaining fuel.

A rail launch system would replace the first rocket stage, which tends to be the largest and most unwieldy one. The first stage of the Saturn V weighed almost four times much as the rest of the rocket put together on takeoff, and it was only used to accelerate it up to 2300 m/s. Increasing delta-v is more expensive the more you have, and even going from 30k km/s to 29 would be a huge saving in take-off mass.

That being said, given the complexity of a rail launch system, I guess it would be far simpler to just use that rocket stage in most cases. It could even be recovered and reused, making it pretty cost-effective per launch. Building such rails aren't cheap, and maintaining them isn't either. A rocket is probably competitive and then some.
I agree that rail launch is a new territory for rocket flight entirely...and pioneer work might take decade to work out.

Certainly being able to replace 10 engines with just one is big leap forward etc. Elon Musk boasts that his Falcon 9 and BFR could reach orbit without the first stage ( without payload ). Rail launch would ensure a working shuttle ( SSTO )....and make space flight much much cheaper than today. It would be more ecological as well. NASA 1994 Maglifter study is not a worthless paper...it is a studied fact.
__________________
My nick is not an Ayn Rand glorification, but a homage to real geniuses in building art !

http://max3fan.blogspot.fi/
fountainkopf no está en línea   Reply With Quote
Sponsored Links
Advertisement
 
Old January 21st, 2019, 07:43 PM   #224
fountainkopf
Registered User
 
fountainkopf's Avatar
 
Join Date: Aug 2013
Location: Endor
Posts: 750
Likes (Received): 179

double post
__________________
My nick is not an Ayn Rand glorification, but a homage to real geniuses in building art !

http://max3fan.blogspot.fi/
fountainkopf no está en línea   Reply With Quote
Old January 22nd, 2019, 04:02 PM   #225
AcesHigh
Taking On The World
 
AcesHigh's Avatar
 
Join Date: Feb 2003
Location: Novo Hamburgo
Posts: 26,281
Likes (Received): 8597

Quote:
Originally Posted by Kyll.Ing. View Post
A spacecraft expends a significant fraction of its fuel (more than a third, according to the quoted Wikipedia paragraph) to achieve 1600 km/h from a standstill.
Please, I did not find the quoted Wikipedia article you mention.

Are you sure it's not 1600 m/SECOND? (from a total of about 9000 m/s needed for orbit). Or 1.6 km/s?

Because coming from a standstill makes no difference.

from 0 to 1600 km/h the energy you need (and thus amount of fuel) is the same as from 1600 to 3200 km/h.

a rocket has mostly constant fuel flow and thus thrust.

the reason its acceleration increases with time is because of the change in fuel mass, which decreases steadily.


Quote:
If you could give the same spacecraft that speed without using any fuel, you could cut a third of the fuel volume, and thus save some mass by shrinking the fuel tanks accordingly, giving you even more mileage out of the remaining fuel.
Not a third. According to the rocket equation, and you can find websites to calculate it, reducing 1600 km/h from 30 thousand km/h will decrease the mass you need in only about 13%.

et's suppose the delta-v to LEO is 30 thousand km/h. You have a rocket with 320 isp and you want to get 50 tons in LEO (payload plus engine weight plus tank weight)

Your rocket will have to weight 712 tons at take off (including fuel)

An initial speed of 1600 km/h would mean your delta v of 28,4 thousand km/h, your initial mass would decrease to 618 tons. 94 tons less.

That's 13%.

I re-did my rocket equation calculation, same parameters, but took your figure of 1600 km/h and changed it to 1600 m/s.

Initial mass fell from 712 tons to 427 tons. That's 40% decrease in initial mass, much closer to the 1/3 you mentioned, making me believe you misquoted the article or the article is wrong, and that the correct is 1600 m/s, not 1600 km/h.


Quote:
A rail launch system would replace the first rocket stage, which tends to be the largest and most unwieldy one. The first stage of the Saturn V weighed almost four times much as the rest of the rocket put together on takeoff, and it was only used to accelerate it up to 2300 m/s. Increasing delta-v is more expensive the more you have, and even going from 30k km/s to 29 would be a huge saving in take-off mass.
it would only replace the first rocket stage it could get your second stage to the upper stratosphere (less air resistance) and to about 8000 km/h instead of only 1000 or 1600 km/h


after all, if you COULD use a second stage, from low height and from just 1600 km/h, why not do it from the start with a rocket stage?

You would need a smaller first stage, only to reach 1600 km/h, then you could drop it.

that the first stage is dropped usually around 8000 km/h shows that is the best optimal performance and that below that, you probably wouldn´t be able to reach orbital velocity with second stage.
__________________
http://gremioemfoco.info/ forum do grêmio, para quem não consegue se conter e falar somente do estádio, uma boa opção
AcesHigh no está en línea   Reply With Quote
Old January 22nd, 2019, 04:29 PM   #226
Kyll.Ing.
Registered User
 
Kyll.Ing.'s Avatar
 
Join Date: Nov 2012
Location: Trondheim
Posts: 1,780
Likes (Received): 5743

Quote:
Originally Posted by AcesHigh View Post
Please, I did not find the quoted Wikipedia article you mention.

Are you sure it's not 1600 m/SECOND? (from a total of about 9000 m/s needed for orbit). Or 1.6 km/s?
Here: https://en.wikipedia.org/wiki/Rocket...of_the_problem

It references this page, which says:

Quote:
To travel that fast, it must reach an altitude above most of Earth's atmosphere so that friction with the air will not slow it down or overheat it. The journey starts relatively slowly: at liftoff, the shuttle weighs more than 2.04 million kilograms (4.5 million pounds) and it takes eight seconds for the engines and boosters to accelerate the ship to 161 kilometers per hour (100 mph.) But by the time the first minute has passed, the shuttle is traveling more than 1,609 kilometers per hour (1,000 mph) and it has already consumed more than one and a half million pounds of fuel.
Quote:
Originally Posted by AcesHigh View Post
a rocket has mostly constant fuel flow and thus thrust.

the reason its acceleration increases with time is because of the change in fuel mass, which decreases steadily.
Also keep in mind that both air resistance and engine Isp changes with pressure, i.e. altitude. The 30 % figure is also quoted from the space shuttle system, whose shape probably was less aerodynamic than that of a single rocket. I'm not sure if that is enough to explain why the number is so much higher than 13 %, but it should have some impact. In any case, the 13 % delivered by the rocket equation probably represents an ideal minimum, with some physical phenomena and various secondary effect pushing it up pretty drastically in practice.
Kyll.Ing. no está en línea   Reply With Quote
Old January 22nd, 2019, 05:08 PM   #227
AcesHigh
Taking On The World
 
AcesHigh's Avatar
 
Join Date: Feb 2003
Location: Novo Hamburgo
Posts: 26,281
Likes (Received): 8597

But if that difference is because of air resistance and isp, launching from 3000 meters won't make that much difference. How many seconds did the shuttle need to reach that altitude?


And anyway, this would be unrelated to launching from rail. You could just build a launch pad in La Paz
__________________
http://gremioemfoco.info/ forum do grêmio, para quem não consegue se conter e falar somente do estádio, uma boa opção
AcesHigh no está en línea   Reply With Quote
Old January 23rd, 2019, 09:31 AM   #228
fountainkopf
Registered User
 
fountainkopf's Avatar
 
Join Date: Aug 2013
Location: Endor
Posts: 750
Likes (Received): 179

Quote:
Originally Posted by AcesHigh View Post
The rail launch makes almost no difference in the deltaV needed for orbit.

You still need a delta V of 29 thousand km/h.

And you must achieve that delta-V with a vehicle with absolutely the wrong aerodynamics for such high speeds.

Yes there was a bit too much wing on it.




Quote:
Originally Posted by AcesHigh View Post
But if that difference is because of air resistance and isp, launching from 3000 meters won't make that much difference. How many seconds did the shuttle need to reach that altitude?


And anyway, this would be unrelated to launching from rail. You could just build a launch pad in La Paz
You keep forgetting the gravity losses on vertical take off..those are 2 km/s..aeroplane does not have those.
__________________
My nick is not an Ayn Rand glorification, but a homage to real geniuses in building art !

http://max3fan.blogspot.fi/
fountainkopf no está en línea   Reply With Quote
Old January 23rd, 2019, 02:46 PM   #229
AcesHigh
Taking On The World
 
AcesHigh's Avatar
 
Join Date: Feb 2003
Location: Novo Hamburgo
Posts: 26,281
Likes (Received): 8597

And you keep forgetting the extra mass and drag from wings make the velocity losses higher for an airplane style SSTO than the gravity loss to a rocket.

Solution? Steeper launch. But then you have more gravity loss
__________________
http://gremioemfoco.info/ forum do grêmio, para quem não consegue se conter e falar somente do estádio, uma boa opção
AcesHigh no está en línea   Reply With Quote
Old January 23rd, 2019, 03:04 PM   #230
fountainkopf
Registered User
 
fountainkopf's Avatar
 
Join Date: Aug 2013
Location: Endor
Posts: 750
Likes (Received): 179

Quote:
Originally Posted by AcesHigh View Post
And you keep forgetting the extra mass and drag from wings make the velocity losses higher for an airplane style SSTO than the gravity loss to a rocket.

Solution? Steeper launch. But then you have more gravity loss
Did you know that the lightest rocket had only 1,7% in the structure...without the engine ?

I can launch M4 if needed.
__________________
My nick is not an Ayn Rand glorification, but a homage to real geniuses in building art !

http://max3fan.blogspot.fi/
fountainkopf no está en línea   Reply With Quote
Old May 20th, 2019, 03:23 PM   #231
lawdefender
Registered User
 
Join Date: Aug 2013
Posts: 1,815
Likes (Received): 2855

China’s LandSpace Successfully Tests TQ-12 Engine

By Annamarie Nyirady | May 17, 2019

https://www.satellitetoday.com/launc...-tq-12-engine/

Chinese private rocket company LandSpace successfully tested an 80-ton thrust liquid oxygen-methane engine, according to its developer Friday. The engine, named TQ-12, was independently developed by LandSpace and has the third-highest thrust level among liquid oxygen-methane engines globally — and is in the same vein SpaceX’s Raptor engine and Blue Origin‘s BE-4 engine.

The TQ-12 engine carried out four firing test runs this week, with the longest run-time being about 20 seconds.

According to the release, the engine is environmentally friendly, low-cost, easy to operate, and reusable. The engine, which can be used in small rockets as well as medium-sized and heavy rockets, has high commercial value, the company said.
__________________
The cities which I had been to: New York city,Washington DC, Boston, Atlantic City, London, Paris, Venice, Amsterdam, Munich, Zurich, Genève, Hong Kong, Singapore, Bangkok, Manila, Taipei, Sydney, Brisbane, Cape Town, Johannesburg, Durban, Port Louis

Last edited by lawdefender; May 20th, 2019 at 06:37 PM.
lawdefender no está en línea   Reply With Quote
Old May 20th, 2019, 03:25 PM   #232
lawdefender
Registered User
 
Join Date: Aug 2013
Posts: 1,815
Likes (Received): 2855

Aiming to Make History, China’s iSpace Plans June Rocket Launch

http://www.sixthtone.com/ht_news/100...ocket%20Launch

Private Chinese rocket company iSpace is planning to launch its first carrier rocket around June 10, the company told Sixth Tone on Wednesday. If successful, iSpace will become the first commercial company in the country to deliver a satellite into low Earth orbit.

The iSpace rocket — known as the Hyperbola 1 Y1, or SQX-1 Y1 — is 21 meters long and weighs 31 tons, making it longer and heavier than the carrier rockets from two private companies that previously attempted the historic flight: Both LandSpace and OneSpace were unsuccessful in those launches, which took place in October 2018 and March of this year, respectively.

China’s private space industry is a new yet already booming sector. Of the country’s 123 private companies specializing in various space fields — such as rocket building and satellite manufacturing — roughly half were established within the past three years. In 2018, over 3.5 billion yuan ($510 million) was funneled into China’s private space industry, a 62% increase compared with the previous year. (Image: Courtesy of iSpace)
__________________
The cities which I had been to: New York city,Washington DC, Boston, Atlantic City, London, Paris, Venice, Amsterdam, Munich, Zurich, Genève, Hong Kong, Singapore, Bangkok, Manila, Taipei, Sydney, Brisbane, Cape Town, Johannesburg, Durban, Port Louis

Last edited by lawdefender; May 20th, 2019 at 06:42 PM.
lawdefender no está en línea   Reply With Quote
Sponsored Links
Advertisement
 


Reply

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT +2. The time now is 05:14 AM.


Powered by vBulletin® Version 3.8.11 Beta 4
Copyright ©2000 - 2019, vBulletin Solutions Inc.
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Feedback Buttons provided by Advanced Post Thanks / Like (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.

SkyscraperCity ☆ In Urbanity We trust ☆ about us