LIVE: SpaceX Falcon 9 (Flight 2) - COTS-1 - Launch Updates - December 8, 2010

[go4mars]

80 percent of the money Congress is expected to devote to heavy-lift development would go toward the standard cost-plus method for funding spacecraft development,

 
That's the 10 billion dollars for the other guys.

with 20 percent going to the kind of fixed-price, milestone-based approach that is being used for the NASA program that's funding SpaceX's effort.[/i]

   
That's the 2.5 billion for SpaceX to make a Superheavy.



2.5/12.5 is 20% for SpaceX to do it's thing.
10/12.5 is 80% for the other guys to do their thing.

[vt_hokie]

What was truly incredible was Elon Musk saying that a future Dragon is being planned to do a full powered landing and land on a helipad similar to landing a helicopter. You would launch on the Falcon 9 achieve orbit and have a powered reentry to a pinpoint landing with parachutes as a backup. That's truly incredible and it totally negates the need for flyback plane type vehicles using runways. Sorry Sierra Nevada, you have just been outsmarted and outclassed. Why have runways when you can land on a pad? By the time Dreamchaser is developed it will have already been ruled unnessessary.   

Well, let's just say, "I'll believe it when I see it..." 

Remember years ago we were all promised jetpacks, flying cars, home nuclear power plants the size of a water heater you buried in the backyard to power your home, and all that...  Heck in the late 40's early 50's the helicopter was promised to eventually replace the automobile... 

I wasn't around back then, but in the 80's and 90's I was promised SSTO spaceplanes by the turn of the century!   

Put me in the "I'll believe it when I see it" category.  But regardless, I don't see how it negates DreamChaser, and I thought one of the benefits of this commercialization plan was supposed to be redundancy through relying on more than just a single type of vehicle.  So, I certainly hope that the success of SpaceX won't put the brakes on other efforts.

[Robotbeat]

Oh, goodness, you guys! Precision landing isn't even necessarily that hard. Soyuz does pretty well land-landing and, heck, to use an extreme example, precision ammunitions do a pretty good job with precision "hard landing." A bunch of folks did it for the Lunar-landing Challenge X-Prize, with enough precision to land in the bed of a pickup truck and all combined for less money than a single Falcon 1 launch.

This is not really that amazing.

EDIT: It's "hard" and amazing, but certainly nothing unrealistic or decades-in-the-future-speculation. I don't want to detract from the hard work of folks like Armadillo Aerospace and Masten Space Systems, but to point out that it isn't far in the future, but has already been basically demonstrated.

[hop]

Oh, goodness, you guys! Precision landing isn't even necessarily that hard. Soyuz does pretty well land-landing

Land landing does not imply precision landing. Soyuz does not do precision landing.

I do agree that precision powered landing is well within reach. Whether it's a win is a different question (IMO, yes), but it's clearly possible with current technology.

[Robotbeat]

Oh, goodness, you guys! Precision landing isn't even necessarily that hard. Soyuz does pretty well land-landing

Land landing does not imply precision landing. Soyuz does not do precision landing.
...

You did read the rest of my post, right?

[NotGncDude]

Oh, goodness, you guys! Precision landing isn't even necessarily that hard. Soyuz does pretty well land-landing and, heck, to use an extreme example, precision ammunitions do a pretty good job with precision "hard landing." A bunch of folks did it for the Lunar-landing Challenge X-Prize, with enough precision to land in the bed of a pickup truck and all combined for less money than a single Falcon 1 launch.

This is not really that amazing.

EDIT: It's "hard" and amazing, but certainly nothing unrealistic or decades-in-the-future-speculation. I don't want to detract from the hard work of folks like Armadillo Aerospace and Masten Space Systems, but to point out that it isn't far in the future, but has already been basically demonstrated.

Not the same. Not the same. The hard part of precision landing a capsule is nailing the entry interface and the atmospheric steering. What the LLC teams demonstrated the "last mile" sort of thing.

[hop]

You did read the rest of my post, right?

Yes. The recent Dragon flight already demonstrated essentially the same capabilities as Soyuz*. If it had hit the ground instead of water, it would have been about the same as a Soyuz without the landing rockets**

It doesn't say anything about the viability or not of Elons powered landing scheme. Neither do precision munitions. (edit: except maybe precision ballistic missile warheads)

* With better accuracy, but that may just be beginners luck
** as has happened on occasion.

[mmeijeri]

Not the same. Not the same. The hard part of precision landing a capsule is nailing the entry interface and the atmospheric steering. What the LLC teams demonstrated the "last mile" sort of thing.

SpaceX has already demonstrated everything but the last mile.

[hop]

SpaceX has already demonstrated everything but the last mile.

Landing near the center of the ellipse once doesn't mean they can do it repeatably.

[Robotbeat]

SpaceX has already demonstrated everything but the last mile.

Landing near the center of the ellipse once doesn't mean they can do it repeatably.

But it suggests that they can.

[martin hegedus]

SpaceX has already demonstrated everything but the last mile.

Landing near the center of the ellipse once doesn't mean they can do it repeatably.

But it suggests that they can.

Sorry, it doesn't suggest anything unless one knows how hard a control system had to work to get to the state required (vs. predicted) and how close the uncertainties (wind, etc) were to nominal.

Edit:  Just because a feedback system is able to minimize it's error doesn't mean it works well.

[Robotbeat]

SpaceX has already demonstrated everything but the last mile.

Landing near the center of the ellipse once doesn't mean they can do it repeatably.

But it suggests that they can.

Sorry, it doesn't suggest anything unless one knows how hard a control system had to work to get to the state required (vs. predicted) and how close the uncertainties (wind, etc) were to nominal.

If they really did get within less than 800m of their target from orbit, that wasn't by chance. They don't have a terminal rocket guidance system, yet, but it seems to suggest to me that they probably have active guidance via the small lift/drag you get from having an angle-of-attack with a capsule and/or Dracos firing while reentering.

Essentially, SpaceX needs only the last mile. Though, that's quite an "only"!

[kraisee]

800m could easily be accounted for as a dispersion between full scale and CFD/Wind Tunnel data.   Mercury, Gemini, Apollo and yes, Shuttle, all had to change their predicted landing target assumptions once hard data began to come in from full scale test flights.   Space-X is not 'unusual' in this regard.

The trend data over the next handful of test flights will be very interesting to see.   It will show the consistency of the design's capabilities to make landing targets.

Space-X have a single point of data now.   It indicates a remarkable degree of accuracy.   But you can't get any trends from a single data point.   We all need to wait and see if Space-X can replicate this success on the next flight, and the next, and then continue producing good results from there.   Time will resolve this question.

Ross.

[Robotbeat]

800m could easily be accounted for as a dispersion between full scale and CFD/Wind Tunnel data.   Mercury, Gemini, Apollo and yes, Shuttle, all had to change their predicted landing target assumptions once hard data began to come in from full scale test flights.   Space-X is not 'unusual' in this regard.

The trend data over the next handful of test flights will be very interesting to see.   It will show the consistency of the design's capabilities to make landing targets.

Space-X have a single point of data right now.   It indicates a remarkable degree of accuracy.   But you can't get any trend data from a single data point.   We all need to wait and see if Space-X can replicate this success on the next flight, and the next, and then continue producing good results from there.   Time will resolve this question.

Ross.

It kind of depends on what you're looking at, though... A single successful event has more significance the less unlikely that it was that it occurred by chance. Your confidence level is still low because it was only a single sample, but it's unlikely it was just chance.

If you go to the range with someone who says they are a marksman and they hit a bullseye at 100m their first and only shot, there's a lot greater reason to believe them than someone who says they can predict the outcome of a coin-flip and does so only once. "Sample size" isn't the only thing to consider.

[martin hegedus]

If they really did get within less than 800m of their target from orbit, that wasn't by chance. They don't have a terminal rocket guidance system, yet, but it seems to suggest to me that they probably have active guidance via the small lift/drag you get from having an angle-of-attack with a capsule and/or Dracos firing while reentering.

Essentially, SpaceX needs only the last mile. Though, that's quite an "only"!

I hope I didn't insinuate it was by chance, because that was not my intent.  I don't know the ins and outs of their control system.  The control system needs a model of the plant, this includes the aerodynamics.  Any uncertainties with the plant model will translate into uncertainties of the control system.  Unfortunately there are a lot of uncertainties with predicting L/D whether one relies on wind tunnel or CFD.  If this is a feedback system (I assume it is), it is good to see that they were able to hit the target.  But it is also important to know how the control system behaved during the full trajectory.  For example, if the angle of attack of the capsule got too close to a margin, for example a highly non-linear aerodynamic region that they would like to avoid, then there is an issue.

[darkenfast]

I may have missed it, but has there been any info released about the arm of the strongback collapsing? I'm wondering if it was either related to the spilled fuel burning or if it was perhaps from the acoustic load that happens when those nine Merlins pass by a few feet away. That has to be a nasty environment!

[Lars_J]

No information about that has been released AFAIK.

[Xentry]

The control system needs a model of the plant, this includes the aerodynamics.  Any uncertainties with the plant model will translate into uncertainties of the control system.  Unfortunately there are a lot of uncertainties with predicting L/D whether one relies on wind tunnel or CFD.

Reentry control for low L/D vehicles is typically simply based on damping the vehicle body rates (capsules tend to be quite stable about the trim angle-of-attack).

Therefore, the only real question related to aerodynamic model uncertainty is the trim AOA profile that the vehicle followed during entry. That's why Elon specifically mentioned in the press conference that they had predicted a maximum of 20% dispersion and only had a 2% difference wrt to the predicted trim AOA. This is significant enough to suggest that the L/D profile they predicted in their aerodynamic analyses was very very close to the actual L/D profile flown.

On the other hand, Elon also mentioned a 4.5g maximum deceleration, which means that they clearly had a net positive L/D trajectory. A net 0 L/D would have meant higher peak deceleration and maximum manoeuvrability (which is used to constrain any system/mission deviations from the nominal trajectory). With net positive L/D it's a more comfortable flight with somewhat smaller manoeuvring margin (TBD).

Finally, the 800m error at splashdown is quite significant. A 50/50 budget for errors accumulated during entry and errors accumulated under a parachute is not uncommon, with numbers such as ~5km landing error typical. It's therefore unlikely for there to have been much wind, and the guidance scheme seems to have worked fine (any small initial position/velocity/atmospheric/aerodynamic errors would typically have evolved to a much larger dispersion at the terminal entry point).
Honestly it would appear they did a pretty good job in terms of their entry system. As to the details of the vehicle dynamics throughout the entry, and in what regards how much fuel they spent to stabilise and control the vehicle, as well as to track their reference trajectory, only they would know...

[NotGncDude]

SpaceX has already demonstrated everything but the last mile.

Landing near the center of the ellipse once doesn't mean they can do it repeatably.

But it suggests that they can.

Sorry, it doesn't suggest anything unless one knows how hard a control system had to work to get to the state required (vs. predicted) and how close the uncertainties (wind, etc) were to nominal.

If they really did get within less than 800m of their target from orbit, that wasn't by chance. They don't have a terminal rocket guidance system, yet, but it seems to suggest to me that they probably have active guidance via the small lift/drag you get from having an angle-of-attack with a capsule and/or Dracos firing while reentering.

Essentially, SpaceX needs only the last mile. Though, that's quite an "only"!

I personally don't believe the 800m but I'd be happy to be corrected. 800m at parachute opening? 800m at splashdown? That one is even harder to believe since the parachute drifts so much.

[Xentry]

I personally don't believe the 800m but I'd be happy to be corrected. 800m at parachute opening? 800m at splashdown? That one is even harder to believe since the parachute drifts so much.

On the other hand, they had their recovery ship next to the floating capsule 35min after splashdown. Considering a maximum speed of 15kt, the recovery ship couldn't have been more than about 15km from the capsule in the first place. It would still have been a good performance.

If they really did get within less than 800m of their target from orbit, that wasn't by chance. They don't have a terminal rocket guidance system, yet, but it seems to suggest to me that they probably have active guidance via the small lift/drag you get from having an angle-of-attack with a capsule and/or Dracos firing while reentering.

800m from their target without a guided entry would have been close to a miracle. Elon specifically mentioned in the NASA press conference that their angle-of-attack during entry was about 12º, and within 2% of the predicted. So they had a lifting entry, and therefore it follows that they were controlling the lift vector direction using thrusters, perhaps in order to follow a reference profile throughout entry (for instance a drag profile, such as for the Shuttle).