Home PageFacebookRSS News Feed
PocketGPS
Web
SatNav,GPS,Navigation
Pocket GPS World - SatNavs | GPS | Speed Cameras: Forums

Pocket GPS World :: View topic - Launching a GPS Satellite into orbit
 Forum FAQForum FAQ   SearchSearch   UsergroupsUsergroups   ProfileProfile   Log in for private messagesLog in for private messages   Log inLog in 

Launching a GPS Satellite into orbit

 
Post new topic   Reply to topic    Pocket GPS World Forum Index -> News And Latest Information
View previous topic :: View next topic  
Author Message
MikeB
Frequent Visitor


Joined: 20/08/2002 11:51:57
Posts: 3859
Location: Essex, UK

PostPosted: Thu Jul 31, 2014 6:22 pm    Post subject: Launching a GPS Satellite into orbit Reply with quote

pocketgpsworld.com
When the GPS Satellite has gone through the processing stages and is mated to the rocket it is ready to be launched into orbit. Our previous article covered the pre-launch processing of the GPS satellite, from conception to delivery and integration with the launch vehicle. This article looks at how the satellite is placed into orbit.

The launch sequence starts two to three days before the planned launch time with a launch readiness review. The results of the review trigger a sequence of events that culminate in the ignition of the rocket engine and the ride through the atmosphere into space. Once again as the next launch will be on an Atlas V rocket we will use that as an example.

The launch readiness review is carried out by the managers of the various teams involved in launching the rocket. This will include the ULA Atlas V booster team, Boeing, USAF Space and Missile group, Ground support, Weather, and Range Safety, amongst others. Each team will provide a status report and providing everything is within the proscribed limits the Launch Readiness Review will recommend progressing towards a launch at the scheduled time.

The GPS Spacecraft is already fully prepared for launch at this time, but will be dormant within the Payload Fairing. There are special environmental control systems which continually monitor temperatures and maintain the correct conditions for the spacecraft. The spacecraft and the environmental systems are connected to the Mobile Launch Platform (MLP) service tower which in turn is provided by services in the Vertical Integration Facility (VIF), the Mobile Service Vehicles, or the Ground Support systems on the launch pad.

Around 8 hours before the launch the Atlas V rocket and the GPS satellite on top of the MLP are pushed out to the launch pad some 570 metres from the VIF in a process known as Roll Out. The path to the launch pad has two parallel rail lines for the MLP to roll along. The MLP is pushed up to the launch pad by a pair of special engines, towing a convoy of generators and support equipment to maintain and monitor the rocket and spacecraft on the short trip to the pad. Although it is only a short distance from the VIF to the Pad it takes around 30 minutes to get there.

Atlas V tracks from the VIF
The rail tracks to transport the MLP to the launch pad
Image credit: Wired4Space.com


Initially after pulling out of the VIF there is a small bend which is taken slowly. Having negotiated the bend the MLP speeds up to about half walking pace for around 300 metres on the straightaway before reaching the slight incline of the approach to the launch pad where it slows down once again. The final creep up to the launch pad completes the last land based movement of the rocket and GPS satellite.

Tha Atlas V rollout convoy
The Atlas V MLP rollout convoy
Image credit: United Launch Alliance


Moving from the VIF to the launch pad can be a little risky for the rocket with all the delicate electronics and systems. Florida is well known as the lightning capital of the world and the short trip to the launch pad would leave it exposed to the possibility of a lightning strike. For this reason the 45th Space Wing of the USAF will have reviewed the surrounding weather and declared the area safe for transport before first movement can take place.

Having arrived at the launch pad the rocket and GPS Satellite are protected by the lightning masts surrounding the pad. Now the ground support team starts to secure the MLP and the rocket. This process called Hard Down. Now all the pipes and cables will be switched from the service convoy to a series of services provided on the launch pad. When this is complete the rocket will be ready for final inspection and fuelling.

The following video is a time lapse of an Atlas V heading out to the launch pad. The 30 minutes of the trip have been compressed down to just over a minute.


Video Credit: Wired4Space.com

For most rocket launches there is a Launch Window when the rocket could be launched. This could be just a few minutes to a few hours. A launch time or T-0 will be set before the countdown starts and will target a time in the launch window for liftoff. Typically this will always be the opening of the window to make the countdown as short as possible. Having a long window allows the possibility of a recycle of the terminal countdown for a second attempt at launching on the same day if a minor fixable issue caused the Hold in the countdown.

The countdown on launch day starts 12 hours 40 minutes before the T-0 launch time at T-12 hours. The countdown is not a linear timeline as it has built-in holds where the clock stops for a period before picking up again and the activities are restarted. These typically occur before fuelling and before the terminal countdown to allow the launch teams to assess the vehicle and weather and make a decision to continue or move the T-0 time to a different part of the launch window. The Atlas V countdown has 2 built-in holds: a thirty minute hold at T-120 minutes prior to fuelling, and a 10 minute hold at T-4 minutes before entering the terminal countdown.

As the countdown starts the launch teams are all polled to ensure that everything is in the correct status to start the countdown. The start of preparations for a launch are initiated on the launch complex. There will be a number of weather briefings throughout the countdown, the first being issued as soon as the countdown starts. There are a number of operations that cannot start if there are adverse weather warnings such as lightning in the vicinity, or strong winds. The built-in holds can help to provide a buffer if weather prevents an operation taking place.

At T-8 hours the the Atlas V is moved to the launch pad after which the pad area will be cleared of personnel for fuelling. Prior to fuelling there will be another weather briefing to allow the tanking to take place. There are a number of gas tanks on the launch pad to process and fill the rocket's tanks: Hydrogen, Nitrogen, Helium, and Oxygen. These need to be conditioned and the pipework and valves between the tanks and the rocket need to be chilled down before the rocket tanks can be filled.

The Liquid Oxygen tank at LC-41
The Liquid Oxygen storage tank at LC-41
Image credit: Wired4Space.com


At T-2 hours and holding the first of the planned holds is entered. By now the launch complex is cleared of all personnel before the start of the tanking operations. During this hold the Launch Conductor collates reports about the readiness of the rocket, satellite and payload. A briefing is conducted where the Launch Director informs the teams of what actions to take if a problem is detected during the fuelling. The Launch Director will poll all the stations to ensure that everything is "GO for Tanking". If all engineers report green then the Launch Director will release the hold.

T-2 hours and counting. With the countdown clock resumed the tanking operations begin. The ground equipment has already been conditioned over the last few hours, and now with permission to fuel the rocket the conditioning of the Atlas V starts. The Atlas V booster will already be filled with the RP-1 (Rocket Propellant - 1 a highly refined form of kerosene) either in the VIF or on the launch pad. RP-1 is a liquid fuel at ambient temperatures and does not require special handling.

The remaining fuel components of the common core booster and Centaur upper stage are cryogenic and need to be kept extremely cold to remain in liquid form. The Centaur upper stage uses Liquid Oxygen (LOX) and Liquid Hydrogen (LH2) whilst the common core booster uses LOX with the RP-1 as fuel sources. The cryogenic fuels (liquid gasses) need to be treated specially whilst storing and transferring into the rockets tanks. This includes a chill down of all the piping and transfer lines as well as the valves and other flow control components. The fuel tanks themselves also have to be chilled down prior to the flow of the cryogenic fuels. This is all done to prevent thermal shock to the system which could cause a fracture resulting in a failure of the rocket.

T-1 hour 40 minutes. The chill down has completed and the fuels begin to flow. The filling starts slowly at first ensuring that everything is functioning correctly. After a short while the tanking transitions to fast fill mode with the tanks filling up rapidly. Once the tanks are nearly full the fuelling mode enters replenishment mode where any of the super cold propellant that boils off is replaced. The plumes of gasses seen streaming from the rocket whilst awaiting launch are the vapours produced from boiling gaseous liquids.

There are various pressurised systems onboard the rocket and each stage has a helium bottle which is used to pressurise these items. The helium is also transferred into the tanks during the fuelling phase. Helium, being an inert gas, is also used to purge the rocket engine chambers of superfluous gasses before the flow of fuel and ignition. This prevents a build up of hydrogen causing a premature ignition or worse explosion.

T-4 minutes and holding. The countdown has now reached the final hold of the launch and this is where the engineers get a chance to catch up with any last minute tasks left outstanding and to ensure that the rocket and satellite are ready for launch. The Launch Director will now poll all the teams including the Range Safety and Weather officers, if all is GREEN then the Mission Director will give the Launch Director permission to launch. With the "GO FOR LAUNCH" result the hold will be released exactly 4 minute before the planed T-0. Now the countdown clock is synchronised with the launch time.

T-4 and counting. The countdown resumes and enters an automated sequence of events culminating in the ignition of the booster engine. At this point the GPS IIF satellite will be switched to internal power and running on battery power. The GPS will not be able to power itself until it is in orbit and the solar arrays are deployed. The satellite is no longer connected to the ground support systems and is now autonomous.

The final flight plan will have been loaded into the avionics computer situated on the top of the Centaur upper stage. This is left until the last minute to enable the engineers to monitor the upper level wind speeds that were sent back from weather balloons that have been released throughout the countdown.

The LOX supply to the main booster is terminated allowing the fuel tank to be pressurised for flight. The fuel is still flowing to the Centaur at this time. At T-2 minutes the Atlas V booster is now at flight pressure and the LOX and LH2 feeds are secured for the Centaur. The common core booster and Centaur upper stage are now transitioned to internal power. At this point in the countdown the rocket is self supporting and there is no connections to the ground support system active. The connections between the launcher tower and the rocket will pull off during the flight.

The Atlas V flame trench at LC-41
The Atlas V Flame Trench and water deluge tanks
Image credit: Wired4Space.com


At T-10 seconds the water of the sound suppression system starts to flow over the MLP and around the exit of the flame trench. The flame trench is a channel directing the exhaust of the engine away from the launch pad.

At T-2.7 seconds the rocket main engine is started and over the next few seconds builds up to full power. A plume of exhaust, steam, flames and dirt is thrown up from the flame trench as the thrust builds. At T-0 the hold downs that were keeping the rocket on the MLP are released and the rocket roars into the sky.

Shortly after clearing the launch pad the avionics command the rocket to do a pitch, roll and yaw manoeuvre to orient it in the correct aspect to achieve orbit at the desired location.

GPS satellite launch on an Atlas V
Liftoff of the GPS IIF-4 satellite on an Atlas V
Image credit: Wired4Space.com


90 seconds after launch with the Atlas V already flying supersonically the vehicle pushes through MAXQ, the area of maximum dynamic pressure. Maximum Dynamic Pressure is where the airframe is under maximum mechanical stress. After the initial liftoff this is the second most critical part of the launch sequence. The payload fairing is protecting the GPS satellite as the rocket flies through this critical part of the flight. From hereon the pressures and stresses on the rocket diminish as it climbs higher into the atmosphere.

T+4 minutes. The rocket is now high in the sky and the atmosphere is getting thinner. The common core booster has just about completed it task of lofting the Centaur upper stage and the GPS Satellite through the densest parts of the atmosphere. Shortly after booster cutoff the first and second stages will explosively separate, and the booster will tumble back to land in the Atlantic Ocean. The centaur RL-10A engine will ignite and continue the journey into space.

As the atmosphere thins the danger of damage to the GPS spacecraft diminishes. The payload fairing is now jettisoned lightening the mass of the remaining rocket as it powers its way into orbit.

Just over 12 minutes after the ignition of the Centaur engine the first of two burns is complete and the stack is now in a temporary transfer orbit. An extended coasting period will take the rocket to about 3 hours 17 minutes from launch. Once the rocket is in the correct orbit the Centaur will re-ignite the engine for a burn of around 90 seconds placing it into the correct orbit.

Once in the correct orbit the Centaur will orientate the GPS Satellite before effecting the separation just under 3.5 hours from launch. The GPS Satellite is now flying on its own and will start to deploy the solar arrays which will provide it with power to charge the internal battery and keep the systems running. With the satellite in operational configuration the control of the GPS satellite is transferred to the ground control team for checkout and insertion into the operational GPS constellation.

The following video shows the launch of GPS IIF-4 the only other GPS satellite to be launched on an Atlas V rocket.


Video Credit: Wired4Space.com

I have obviously only scratched the surface of a lot of the processes and procedures that form the deployment of a GPS satellite. It can be seen from this that it is not a simple matter of just hooking up a spacecraft on a rocket and lighting the fuse. A lot of intricate planning, control and execution goes into each and every launch.
email icon

_________________
Mike Barrett
Back to top
View user's profile Send private message Visit poster's website
tenorman
Occasional Visitor


Joined: Mar 19, 2011
Posts: 6

PostPosted: Fri Aug 01, 2014 7:27 am    Post subject: gps sat launch Reply with quote

Well if you read what's happening down under in NZ you would see we have a new company formed that will be launching Sats at about 10% of the current cost over there. They have really started something and you won't need all this fuss anymore. Smaller rocket and uses about as much fuel as a 747 uses flying from Auckland to Christchurch (a 1 hour trip).
It's on "stuff" here in NZ under tech section....great
Back to top
View user's profile Send private message
MikeB
Frequent Visitor


Joined: 20/08/2002 11:51:57
Posts: 3859
Location: Essex, UK

PostPosted: Fri Aug 01, 2014 12:03 pm    Post subject: Re: gps sat launch Reply with quote

tenorman wrote:
Well if you read what's happening down under in NZ you would see we have a new company formed that will be launching Sats at about 10% of the current cost over there. They have really started something and you won't need all this fuss anymore. Smaller rocket and uses about as much fuel as a 747 uses flying from Auckland to Christchurch (a 1 hour trip).
It's on "stuff" here in NZ under tech section....great

I was unable to find the article you mentioned, if you could find the link it would be great.

I am well aware of projects like Skylon which will deploy spacecraft via a horizontal take-off and landing from a normal airport runway. In theory these can rapidly turn around delivering multiple payloads in a day.

Having said that these are unproven technologies, which need more investment and development. Hopefully that will come in time and reduce the costs and improve the process. However a lot of the processes will still need to be followed as they relate to the spacecraft, and no doubt over time the launch process will become more complex as the systems evolve.

A good example of this is the initiative launched by SpaceX who claim to reduce costs and introduce reusability. Although they have come a long way in ten years they are still over promising and underachieving. They learn from each launch and as they do their processes become more complex. This complexity also brings reliability.
_________________
Mike Barrett
Back to top
View user's profile Send private message Visit poster's website
tenorman
Occasional Visitor


Joined: Mar 19, 2011
Posts: 6

PostPosted: Fri Aug 01, 2014 10:33 pm    Post subject: Rocket Reply with quote

here is the link to the NZ company
http://www.rocketlabusa.com/
I may have exaggerated a bit on the cost but it is certainly a lot less than the ones in the Northern territory.
Back to top
View user's profile Send private message
MikeB
Frequent Visitor


Joined: 20/08/2002 11:51:57
Posts: 3859
Location: Essex, UK

PostPosted: Sat Aug 02, 2014 3:46 pm    Post subject: Reply with quote

Ahh but the problem with this is twofold. Firstly it is still 1940s technology :P It is basically a scaled down version of an Atlas or Delta rocket. Secondly it needs to loft around 10 times more mass into orbit for a GPS satellite, these weigh about 1,200kg somewhat over the capacity of the Electron.

Having the same technology LOX/RP-1 then the launch process will be pretty much the same as for an Atlas as detailed in the article.

What would be far more revolutionary would be the Skylon http://www.reactionengines.co.uk/space_skylon_tech.html This is a horizontal take off and landing space plane which has a normal air breathing engine at lower altitudes. As the craft attains higher altitudes the engine then becomes cryogenic using LOX/LH2 propellants in the same engine to achieve orbit.

This is slated as being able to carry 12,000kg but only to Low Earth Orbit. There would still need to be an additional stage to loft it further to 11,000 miles where the GPS satellites fly.
_________________
Mike Barrett
Back to top
View user's profile Send private message Visit poster's website
tenorman
Occasional Visitor


Joined: Mar 19, 2011
Posts: 6

PostPosted: Sun Aug 03, 2014 12:14 am    Post subject: Reply with quote

Ok Fine. I am not into these things really and don't understand the finer points. It just made interesting reading for such a small country as ours and goes to show we down here can do most anything....except win as many gold medals as you do !!!
Back to top
View user's profile Send private message
MikeB
Frequent Visitor


Joined: 20/08/2002 11:51:57
Posts: 3859
Location: Essex, UK

PostPosted: Sun Aug 03, 2014 10:28 am    Post subject: Reply with quote

tenorman wrote:
Ok Fine. I am not into these things really and don't understand the finer points. It just made interesting reading for such a small country as ours and goes to show we down here can do most anything....except win as many gold medals as you do !!!


Great things are happening in lots of 'small' countries. There is a perception that the space technologies are dominated by America and Russia, but now Japan, India, and China are also big players. Not to forget the European consortium ESA.

Interestingly a lot of the smaller countries like NZ and the UK contribute a lot to space exploration. The more the better as far as I am concerned.
_________________
Mike Barrett
Back to top
View user's profile Send private message Visit poster's website







Posted: Today    Post subject: Pocket GPS Advertising

Back to top
Display posts from previous:   
Post new topic   Reply to topic    Pocket GPS World Forum Index -> News And Latest Information All times are GMT + 1 Hour
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum

Make a Donation



CamerAlert Database

Click here for the PocketGPSWorld.com Speed Camera Database

Download Speed Camera Database
22.034 (27 Mar 24)



WORLDWIDE SPEED CAMERA SPOTTERS WANTED!

Click here to submit camera positions to the PocketGPSWorld.com Speed Camera Database


12mth Subscriber memberships awarded every week for verified new camera reports!

Submit Speed Camera Locations Now


CamerAlert Apps



iOS QR Code






Android QR Code







© Terms & Privacy


GPS Shopping