Space X - Dragon Launch Today

[Eric Mc]

Due to launch at 4.55 am EDT. That should be 9.55 BST

This will be the first launch of an unmanned Dragon capsule to dock with the International Space Station.

NASA TV begins its launch coverage at 8.30 am our time.

[Eric Mc]

NASA TV and Spaceflight Now are now broadcasting the run up to the launch this morning -

http://spaceflightnow.com/falcon9/003/status.html

[Eric Mc]

I lost my internet conection a couple of minutes ago. Slight panic stations as I tried to reconnect before lift off.

[Eric Mc]

I was wondering about that. It's either a sound system anomaly or perhaps bird scarers.

[Eric Mc]

Oops.

[Eric Mc]

I bet an oxygen or hydrogen pressurisation line failed to disconnect at Zero.

[Eric Mc]

It'll almost be definitely a scrub for today. Until they find out for sre what the problem was the rocket will be going nowhere.

Just reported that the chamber pressure in Engine 5 was too high which triggered the shut down.

[Eric Mc]

72 hours scrub.

Launch Tuesday morning - if they fully understand why the chamber pressure was too high and what they need to do to make sure it doesn't happen again.

[Eric Mc]

Apparently, today's launch window duration was only 1 second - according to Spaceflight Now. That was a bit tight.

[Eric Mc]

You cannae ignore the laws of physics, cap'n.

[Eric Mc]

Ross1988 said:

Out of interest, what is required for a launch window? I assume there's a lot of variables involved.

Launch windows vary depending on the aim of the mission. If it is just a simple earth orbit but non-rendezvous or non-docking type mission, then there is no window at all - apart from maybe hours of daylight windows or weather windows.

If the spacecraft is going to meet up with another spacecraft in earth orbit, such as the ISS,. then the launch window will be primarilly restricted to a period of time within which the ascending spacecraft will achieve an orbit that puts it in the same orbital plane as the target spacecraft.
This will vary depending on the ability of either spacecraft to change their orbital planes once they get into orbit. I would expect that the Dragon will be quite limited in this respect so it will be depending on the initial booster rocket stages to put it where it needs to be in space. This is how the Soyuz system works.

Apollo was very versatile because it had a sod-off (technical term) Service Propulsion System at the back end of the Service Module which allowed it quite a bit of flexibility once it got into space. The upcoming Orion spacecraft will also have similar capabilities. The Shuttle, on the other hand, was a bit limited - although that was as much to do with the sheer weight of the Orbiter as opposed to available manoeuvering rockets.

If a spacecraft is heading out into the Solar System, then the launch windows will be determined by the relative positions of the moon or planets. Moon launch windows occur every month. Planetary launch windows can be years apart.

Edited by Eric Mc on Saturday 19th May 11:21

[Eric Mc]

Mods - any chance of correcting the typo in the thread title? It should be "Dragon".

[Eric Mc]

They have been working closely with NASA so I would expect that NASA will have shared some of these techniques with them. Indeed, it is NASA's obligation to share such information. That's what they were set up to do.

[Eric Mc]

And the BST time?

[Eric Mc]

Watching the countdown now. Let's hope it gets off the ground this morning.

[Eric Mc]

T-10 minutes.

[Eric Mc]

Apparently, the scrub last Saturday was caused by a purge valve remnaining open, allowing oxygen to back feed into the combustion chamber - thereby increasing the pressure and temperature in the chamber when the engine was lit.

The launch could probably have continued but the criteria for an automatic shut-off was exceeded and the computers shut everything down.

[Eric Mc]

It has a great old fashioned look to it. It reminds me of the older versions of the Atlas.

[Eric Mc]

In orbit. Solar panel deploy next.

[Eric Mc]

Einion Yrth said:

Well, that was the easy bit - Now we get to see if their on-orbit manoeuvering is up to scratch.

I don't think they have to do a lot of orbital plane shifting to reach the ISS. Unlike the Shuttle which had a resonable ability to change its orbital plane (although not as good as Apollo), the Dragon is more like a Soyuz in that the booster rocket is intended to put the spacecraft more or less on course for its rendezvous target. It will only need minor atitude thruster firing to nudge it close to the ISS where it will be grabbed by the remote manipulator arm and "docked" manually by the ISS crew.

PA man has just said that the boost and coast phase brings it to within 37 miles of the ISS. The small thrusters will alter the course slightly to bring it closer to the point where it can be grabbed.