adiggs
Well-Known Member
Totally has nothing to do with anything, but the Tom Lehrer reference made me go fishing for New Math.
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Yes, it's a fun and simply stated problem - and good point about the non-man-rated landings.
I looked once more at the landing in hi-res and contrary to my expectation it looks like OCISLY is not pointing its bow (or most narrow end) up against the wind.
So apart from my fancy in-the-deck electro magnets, it seems like the risk of the rocket stage blowing over board could be reduced just by orienting the deck with its longer side parallel to the general direction of the wind.
I also could not help thinking about Elon Musk's statement about how a highly energetic rocket stage could punch a hole in the landing deck. So here is another idea:
Use a catamaran as a landing ship, for these advantages:
1) One hull along each of the two sides means that the deck can more easily be made larger and especially less rectangular,
2) It should be more economical to create a larger deck in this manner,
3) For a large size deck, a catamaran should offer more stability,
4) In case a rocket stage would actually punch a hole in the (central part of the) deck, it would only proceed into the sea water below, and not cause hull damage nor compromise the seaworthiness of the ship.
Here is a really cool advantage (I think):
5) The rocket engine cannot be throttled very far down, so the landing is hard to control because you have too much thrust just a the point of landing, which makes it critical to turn off the engine just at the right moment. Now, if there is only sea water below the central part of the landing deck, the deck could actually be perforated, with holes dimensioned so the minimum thrust of the single rocket engine would be more suitable for the touch down. Since the deck is likely a sandwich construction, each hole could consist of a pipe connecting the deck layers, providing additional strength.
Obviously, I will be watching the next Falcon 9 launch, still scheduled for the 28th, 11 days away...
As far as I can tell a ship like that would reach about as high as the rocket stage itself when standing on OCISLY.
So for its final length of descent the rocket stage will gradually enter into the lee of the ship where there will be little or no side wind (assuming the ship lies upwind of OCISLY).
As the lower part of the stage passes into the lee, there will thus be a lack of a lateral force on it, compared to the upper part that is still exposed to the side wind, blowing away from the ship.
This will effectively push the lower end of the rocket stage towards the ship providing the lee. This could make the landing harder to control. I think.
On reflection, this "cool advantage" is non-sense. Once the rocket propellant has been expelled from the booster stage, it makes no difference to the booster stage whether the propellant subsequently hits the landing deck or the water...
Sorry about that.
I'm still of the opinion that a Texas Tower-type seafloor-anchored facility is an extremely intriguing option. Some features, pro & con:
- Its inherent stability is, of course, its most prominent advantage
- It presents zero advantages to a floating platform wrt winds qua winds (that is, for keeping the booster on course)
- Booster still would need to be transferred from TTower to a transport vessel - although an integrated crane would be the obvious choice
- Launch trajectory from Canaveral or Vandenberg would have to correspond to site of TTower - assuming just one per launch site
- Any damage repairs would have to be performed on-site rather than back at port, as with barge
But wouldn't the deciding factor be the wind at the launch site more than that on the ocean?
Naturally, SpaceX could add the ocean wind speed to the launch constraints, but this extra constraint would go against the interest of the payload owner, who doesn't care about the first stage retrieval.
Maybe SpaceX could charge less for a launch where they get to wait for low winds also out to sea.
I didn't explain properly--My guess is that the launch criterial/limits/rules for weather likely envelopes the acceptable conditions on the barge. In other words, if you're okay to launch, you're probably okay to land.
Conversely, If the winds/seas are too rough to land, the launch is probably red on weather anyway.
Conversely, If the winds/seas are too rough to land, the launch is probably red on weather anyway.
I understand, but I also did not explain properly. Btw, a link to the Falcon 9 launch constraints can be found here:
Launch commit criteria - Wikipedia, the free encyclopedia
The ocean-landing site is on the order of 300 km out to sea and although the weather conditions there may very well be correlated with those at the launch site, they can certainly also be different and worse. So, yes, there is probably a good chance that OK launch conditions will occur along with OK ocean-landing conditions, but this is not a given.
Also, unless the customer paying for the launch gets a discount that customer will have no reason to accept a postponement due to poor ocean-landing conditions and may very well press for a launch, even if the landing conditions are poor.
I guess once Space X gets more experience with these landings, we might see specific ocean-landing conditions as possible parameters in a launch contract - since a customer's accept of additional constraints for landing conditions should increase the chance of booster retrieval and thus savings for Space X, that can be passed on to the customer.
Alternatively, if SpaceX can choose their booster on a sufficiently short notice, then they can opt to use an already much-used first stage if weather forecasts predict poor conditions at the ocean-landing site.
I'd guess that once they achieve sufficient volume, they will build a new ship that has a gyroscopic deck. That won't help the winds, but it will guarantee a level landing area in any reasonable wave case. Then they only have wind to deal with.
I think a sea floor anchored facility is not practical because there are multiple launch vectors from Cape Canaveral. If I'm not mistaken CRS8 was a NE vector and the previous geo-transfer launch was a SE vector. On the other hand, I think almost all of the Vandenberg launches are pretty much due South.
Ubbe
Member
Found this video of the booster returning on a trailer, cool:
..And this one of the booster being loaded on the trailer:
..And this one of the booster being loaded on the trailer:
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These videos emphasize an important point about how SpaceX manages to keep their costs as low as they do. The F9 is a pretty small rocket compared to most of the others that deliver similar payloads to orbit. SpaceX can transport their boosters and stages pretty easily since they can travel on regular roads. This is critical when your factory is in California but your launch site is in Florida. When SpaceX starts moving into much larger sized rockets, it's going to get a lot more difficult and expensive. FH is an exception since that uses the same size boosters and stages, just more of them.
Maybe SpaceX will buy a second factory for BFR in Florida or Texas and keep Hawthorne for F9 and FH.
Maybe SpaceX will buy a second factory for BFR in Florida or Texas and keep Hawthorne for F9 and FH.
BluestarE3
Active Member
Mod note: Several posts moved to a new thread re: Reusability of Falcon Heavy and multiple boost stages
I ran across this incredible tilt-shift edit of the landing. All credit to /u/saxmanatee on reddit, who labored on it, and apparently edited it frame by frame to get the effect.
That's a remarkable rendering- great to watch. Reminds me a lot of The Thunderbirds....
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