SpaceX Falcon 9 v1.1 - CASSIOPE - September, 2013 - GENERAL DISCUSSION THREAD

[averagespacejoe]

I will be watching July pretty closely because of they can turnaround CASSIOPE and then SES 8 in three weeks then August for Thaicom and September/October for Orbcomm is believable.

[Robotbeat]

It wouldn't be that different if you shot it at an angle or straight up. In fact, the one straight up would have significantly higher reentry forces (and, I believe, heat load).

It might have a higher peak heat flux but the total heat load would likely be greater for a flatter entry trajectory due to the longer time spent traveling through thicker atmosphere.

I don't see why it'd be higher, except perhaps if you're including the initial ascent (pre-staging).

[Robotbeat]

Well, well, well......

SFN now lists this flight at July 9 at 9-11 am PDT (16:00-18:00 GMT). Surely not three F9's in July!? (or heck five F9-1.1 between July and November?)

Edit: Thaicom 6 launch date now listed in August, so at most only 2 F9s in July. (but the second possibility still stands!)

Now that's more realistic (except the two in one month part).

We shall see once they get the first stage acceptance tested. If they can get it acceptance tested by the end of May, they have a shot at getting the first launch off by the end of July.

I like SpaceX, but I still think my 3 launch estimate for 2013 isn't pessimistic... I now think they might POSSIBLY get 4, by I would be incredibly skeptical unless they actually do launch successfully by July.

[kevin-rf]

I will be watching July pretty closely because of they can turnaround CASSIOPE and then SES 8 in three weeks then August for Thaicom and September/October for Orbcomm is believable.

Since they are different pads, I'll give you SES8, but three weeks I suspect is pushing it. I also question less than four weeks from the same pad. SES8,Thaicom,Orbcomm. That said, they still have a chance of all four by the end of October. But I fear I have more of a chance of Jim saying this over optimistic, than all four v1.1 flying by the close of October. But I would like an October surprise.

[deltaV]

It might have a higher peak heat flux but the total heat load would likely be greater for a flatter entry trajectory due to the longer time spent traveling through thicker atmosphere.

I don't see why it'd be higher, except perhaps if you're including the initial ascent (pre-staging).

IANARS but this is how I understand it. Most of the orbital energy (which is a substantial fraction of the energy in the propellant used to launch it) heats the atmosphere rather than the vehicle itself, so conservation of energy is insufficient to determine how heat loads vary (or not). A while ago someone on these forums introduced me to an empirical formula for reentry heat loads, the name of which I've unfortunately forgotten. IIRC that formula gave the heat rate as proportional to the square-root of (the dynamic pressure divided by the radius of curvature), times the airspeed to some small power (1.6 or something like that). Drag is (approximately) proportional to dynamic pressure, so time spent decelerating (from reentry speed to zero assuming dynamic pressure is steady) is inversely proportional to dynamic pressure. Therefore the total heat load is inversely proportional to the square-root of dynamic pressure, i.e. a higher acceleration reentry has higher peak heat rates but lower total heat load (i.e. integral of heat rate). This argument has a lot of unjustified approximations, but the qualitative conclusion is apparently valid: http://en.wikipedia.org/wiki/Atmospheric_entry#Entry_vehicle_design_considerations .

Edit: this is getting off-topic.

[Robotbeat]

It might have a higher peak heat flux but the total heat load would likely be greater for a flatter entry trajectory due to the longer time spent traveling through thicker atmosphere.

I don't see why it'd be higher, except perhaps if you're including the initial ascent (pre-staging).

IANARS but this is how I understand it. Most of the orbital energy (which is a substantial fraction of the energy in the propellant used to launch it) heats the atmosphere rather than the vehicle itself, so conservation of energy is insufficient to determine how heat loads vary (or not). A while ago someone on these forums introduced me to an empirical formula for reentry heat loads, the name of which I've unfortunately forgotten. IIRC that formula gave the heat rate as proportional to the square-root of (the dynamic pressure divided by the radius of curvature), times the airspeed to some small power (1.6 or something like that). Drag is (approximately) proportional to dynamic pressure, so time spent decelerating (from reentry speed to zero assuming dynamic pressure is steady) is inversely proportional to dynamic pressure. Therefore the total heat load is inversely proportional to the square-root of dynamic pressure, i.e. a higher acceleration reentry has higher peak heat rates but lower total heat load (i.e. integral of heat rate). This argument has a lot of unjustified approximations, but the qualitative conclusion is apparently valid: http://en.wikipedia.org/wiki/Atmospheric_entry#Entry_vehicle_design_considerations .

I will grant that conservation of energy is insufficient by itself, here. I'm just not entirely convinced that the total heat flux will be higher in the specific case of taking longer to reenter...

I will acknowledge that for ablative heat shields at VERY high reentry speeds that it's better to go hot-and-quick, but I'm not entirely convinced this can be generalized to lower speeds, since ablative materials are pretty darned non-linear... I've studied these equations as well... this is a difficult question that may very well depend on some of the simplifying assumptions we make...

On the flip side, I don't have a solid case to make that the heat load will be lower for flatter reentry.

[Robotbeat]

I can see flying less than once per month on the same pad, but it'd take more practice than SpaceX will have by the end of this year for darned sure.

[padrat]

A lot of it depends on what state the hardware is in when we get it. The next couple are quite complete based on our guys that have seen them. The question will be if Hawthorne can maintain that level of finish past the next couple rockets...

[subzero788]

I've been out of the loop for a while-- what's the status of the Vandenberg pad? Is it ready to go and it's the launch vehicle acceptance testing that they're waiting on?

[simonbp]

That sounds right. Last I saw, the vehicle is in Texas on the test stand. Once that's done, they'll truck it back to California.

Of course, many things can crop up after arriving at the launch pad...

[mlindner]

That sounds right. Last I saw, the vehicle is in Texas on the test stand. Once that's done, they'll truck it back to California.

Of course, many things can crop up after arriving at the launch pad...

Jim stated that the delay from June to July for the launch was because of launch site construction delays.

[ClaytonBirchenough]

http://www.newspacewatch.com/articles/spacex-moving-quickly-towards-fly-back-first-stage.html

snip

During the NASA/SpaceX teleconference on the CRS-2 mission, Elon Musk confirmed the rumors that they will do a propulsive return test on the upcoming flight of the new Falcon V1.1. He expanded on this to say they will continue doing such tests until they can do a return to the launch site and a powered landing.

For the upcoming flight, after stage separation the first stage booster will do a burn to slow it down and then a second burn just before it reaches the water.

In subsequent flights they will continue these over-water tests. He repeatedly emphasized that he expects several failures before they learn how to do it right.

If all goes well with the over-water tests, they will fly back to launch site and land propulsively. He expects this could happen by mid-2014. Since they don't know how many tests they will need, they don't know exactly which flight this would be.

This is a very accelerated schedule from what most people expected. If they succeed at flying back and landing the first stage, that would be a real revolution in space transport.

Does anyone know to what extent the powered descent for this flight would be? Also, should propulsive descent be added to the list of new "hardware"?

[Lars_J]

http://www.newspacewatch.com/articles/spacex-moving-quickly-towards-fly-back-first-stage.html

snip

During the NASA/SpaceX teleconference on the CRS-2 mission, Elon Musk confirmed the rumors that they will do a propulsive return test on the upcoming flight of the new Falcon V1.1. He expanded on this to say they will continue doing such tests until they can do a return to the launch site and a powered landing.

For the upcoming flight, after stage separation the first stage booster will do a burn to slow it down and then a second burn just before it reaches the water.

In subsequent flights they will continue these over-water tests. He repeatedly emphasized that he expects several failures before they learn how to do it right.

If all goes well with the over-water tests, they will fly back to launch site and land propulsively. He expects this could happen by mid-2014. Since they don't know how many tests they will need, they don't know exactly which flight this would be.

This is a very accelerated schedule from what most people expected. If they succeed at flying back and landing the first stage, that would be a real revolution in space transport.

Does anyone know to what extent the powered descent for this flight would be? Also, should propulsive descent be added to the list of new "hardware"?

The consensus on this forum (based on what we have heard) is that they will attempt do two engine restarts - one to reduce velocity before atmospheric entry to prevent breakup, and a final burn shortly before impact to reduce velocity to 0 just above the water. A simulated landing on water without any legs.

Plans may change. And they may not get that far on the first attempt. But that appears to be the goal.

[guckyfan]

Does anyone know to what extent the powered descent for this flight would be? Also, should propulsive descent be added to the list of new "hardware"?

As I understand it, new hardware related to reusability is the cold gas thrusters for attitude control and the avionics placed on the first stage. Legs will need to be attached later when the first attempt of fly back and land landing will be made.

Edit: Plus the restart ability to some of the first stage engines.

A lot of other hardware changes are related to the general upgrade to 1.1.

Did I miss anything major?

[ClaytonBirchenough]

http://www.newspacewatch.com/articles/spacex-moving-quickly-towards-fly-back-first-stage.html

snip

During the NASA/SpaceX teleconference on the CRS-2 mission, Elon Musk confirmed the rumors that they will do a propulsive return test on the upcoming flight of the new Falcon V1.1. He expanded on this to say they will continue doing such tests until they can do a return to the launch site and a powered landing.

For the upcoming flight, after stage separation the first stage booster will do a burn to slow it down and then a second burn just before it reaches the water.

In subsequent flights they will continue these over-water tests. He repeatedly emphasized that he expects several failures before they learn how to do it right.

If all goes well with the over-water tests, they will fly back to launch site and land propulsively. He expects this could happen by mid-2014. Since they don't know how many tests they will need, they don't know exactly which flight this would be.

This is a very accelerated schedule from what most people expected. If they succeed at flying back and landing the first stage, that would be a real revolution in space transport.

Does anyone know to what extent the powered descent for this flight would be? Also, should propulsive descent be added to the list of new "hardware"?

The consensus on this forum (based on what we have heard) is that they will attempt do two engine restarts - one to reduce velocity before atmospheric entry to prevent breakup, and a final burn shortly before impact to reduce velocity to 0 just above the water. A simulated landing on water without any legs.

Plans may change. And they may not get that far on the first attempt. But that appears to be the goal.

Any idea what the mass penalty in fuel is?

[Danderman]

Is there going to be  a landing attempt for this particular mission?

 

[Jason1701]

Is there going to be  a landing attempt for this particular mission?

 

Yes, on the ocean... been reported numerous places.

[Danderman]

Is there going to be  a landing attempt for this particular mission?

 

Yes, on the ocean... been reported numerous places.

I went back through the whole thread and could not find a definitive answer to my question.

Elon has stated that there will be re-entry tests, but didn't state that this mission would feature a test.

There was a reported rumor that there would be a test during this mission, but no confirmation.

Then, there was a lot of speculation about the nature of the test, but no confirming information.

[mlindner]

Is there going to be  a landing attempt for this particular mission?

 

Yes, on the ocean... been reported numerous places.

I went back through the whole thread and could not find a definitive answer to my question.

Elon has stated that there will be re-entry tests, but didn't state that this mission would feature a test.

There was a reported rumor that there would be a test during this mission, but no confirmation.

Then, there was a lot of speculation about the nature of the test, but no confirming information.

http://shitelonsays.com/transcript/crs-2-post-landing-teleconference-2013-03-27

[Danderman]

Is there going to be  a landing attempt for this particular mission?

 

Yes, on the ocean... been reported numerous places.

I went back through the whole thread and could not find a definitive answer to my question.

Elon has stated that there will be re-entry tests, but didn't state that this mission would feature a test.

There was a reported rumor that there would be a test during this mission, but no confirmation.

Then, there was a lot of speculation about the nature of the test, but no confirming information.

http://shitelonsays.com/transcript/crs-2-post-landing-teleconference-2013-03-27

Reading the transcript, there is nothing that states that the Falcon 9 will be recovered during this flight (or that some recovery procedures would be tested); in fact, Elon only refers to CRS-3 in this context.