Quote from: TrevorMonty on 12/05/2013 04:05 pmIf they are going land it at a remote location. It will need to have good road access so they can truck it out.Spacex may need to demo a few successful landings before being allowed to land at pad.One can assume it will not be landing to far inland, so all they need is a good hovercraft
If they are going land it at a remote location. It will need to have good road access so they can truck it out.Spacex may need to demo a few successful landings before being allowed to land at pad.
Quote from: macpacheco on 12/09/2013 05:05 pm I know Elon said F9R performed better than expected, but we don't know how much better !He quoted the engines running at about 85% capacity. Not sure how exactly that translates to fuel efficiency though.
I know Elon said F9R performed better than expected, but we don't know how much better !
Quote from: Wetmelon on 12/09/2013 07:12 pmQuote from: macpacheco on 12/09/2013 05:05 pm I know Elon said F9R performed better than expected, but we don't know how much better !He quoted the engines running at about 85% capacity. Not sure how exactly that translates to fuel efficiency though.Less thrust, more gravity losses.
Quote from: IRobot on 12/09/2013 08:30 pmQuote from: Wetmelon on 12/09/2013 07:12 pmQuote from: macpacheco on 12/09/2013 05:05 pm I know Elon said F9R performed better than expected, but we don't know how much better !He quoted the engines running at about 85% capacity. Not sure how exactly that translates to fuel efficiency though.Less thrust, more gravity losses.Due to what, the increased fuel mass at each point in the profile?
I'm really happy with this rocket design. It's an incredibly capable vehicle. It's actually one of the biggest rockets in the world, it's worth noting, at about 1.3 million pounds of thrust, and we're only actually operating the engines at about 85% of their potential. Down the road, in future missions, we anticipate being able to crank them up to their full thrust capability, which would give about 165,000 pounds of sea-level thrust per engine. Anyway, it really is something that is, I think, going to serve really well for the commercial launch market, for government satellites and for Dragon, both crew and cargo. I believe its inherent reliability potential is better than any other rocket in the world. It will be up to us to show that it lives up to that reliability potential.
To reiterate what he actually said:Quote from: Elon MuskI'm really happy with this rocket design. It's an incredibly capable vehicle. It's actually one of the biggest rockets in the world, it's worth noting, at about 1.3 million pounds of thrust, and we're only actually operating the engines at about 85% of their potential. Down the road, in future missions, we anticipate being able to crank them up to their full thrust capability, which would give about 165,000 pounds of sea-level thrust per engine. Anyway, it really is something that is, I think, going to serve really well for the commercial launch market, for government satellites and for Dragon, both crew and cargo. I believe its inherent reliability potential is better than any other rocket in the world. It will be up to us to show that it lives up to that reliability potential.http://shitelonsays.com/transcript/spacex-ses-8-pre-launch-conference-2013-11-24I'm not sure why there's any need to "interpret" what he said.. he did use numbers.
Rocket engines are designed for a specific thrust. It's generally known as 100%. Now after they are actually built, tested, and flown it is often found that they have some extra reserve preformance. The Space Shuttle main engines were this way. Later in the program they would run at 104% with the abort option of 109%. Elon's comment indicates that SpaceX thinks that the Merlin 1D can run up to 115%. To make maximum use the rocket would need to grow by that same 15%. Without changing the rocket it only gets you a little extra performance. You get a little less gravity losses because the rocket can climb out faster and burn out sooner. It also helps a lot with an engine out. Since 9 engines at 100% is actailly slightly less than 8 at 115% you have great engine out capability.A oversimplified first order approximation would be the stage burns out 15% sooner. If I remember correctly the first stage runs for about 180 seconds. At 115% fuel use it would be 154 seconds. That cuts 9.8 * 27 seconds or 264 m/s of gravity loss. It's actually less since the first stage throttles some at the end. Maybe 250 m/s. That's not insignificant. A good use might be adding some more fuel to the second stage and reducing the staging velocity to make recovery easier..
If 2 out of 3 launches uses a recovered 1st stage, they only need to build 7 stages a year to support a 21 core a year launch rate which should be with in their current manufacturing capablities. No need to build another factory which is another big saving.
When engineering says that we should be able to get another 15%, management hears "we were only running at 85%."
Quote from: QuantumG on 12/10/2013 05:11 amTo reiterate what he actually said:Quote from: Elon MuskI'm really happy with this rocket design. It's an incredibly capable vehicle. It's actually one of the biggest rockets in the world, it's worth noting, at about 1.3 million pounds of thrust, and we're only actually operating the engines at about 85% of their potential. Down the road, in future missions, we anticipate being able to crank them up to their full thrust capability, which would give about 165,000 pounds of sea-level thrust per engine. Anyway, it really is something that is, I think, going to serve really well for the commercial launch market, for government satellites and for Dragon, both crew and cargo. I believe its inherent reliability potential is better than any other rocket in the world. It will be up to us to show that it lives up to that reliability potential.http://shitelonsays.com/transcript/spacex-ses-8-pre-launch-conference-2013-11-24I'm not sure why there's any need to "interpret" what he said.. he did use numbers.I think Elon likes to play with us by given incomplete information When he talks about 85% and "full thrust capability" is he using the design requirement as the 100% reference? Looking at their site, they advertise 147,000 lbf per engine at sea level. That is 89%, close to the 85% mark.So the current F9 at 147,000 lbf seems to be the 100% rated and the future upgrades will enable a jump to 112%.