SpaceX reusable launcher (Grasshopper) thread 2


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flyingskippy

Doc,

With the results of the previous reentry test showing that it went into an induced spin. Do you know if SpaceX plans on lowering the legs during reentry to help stabilize it?

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DocM

They haven't expressly said the legs will be deployed, but it is expected by just about all observers. Why mount them otherwise?

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Beittil

Well, on the other hand one could expect them to keep the legs folded up just to see if their mere presence can stablize the decent!

 

Then again, if you mean to eventually land... you are going to have to unfold them anyway. The question that now remains is, when is the best time to unfold em? (eg, early on for stability or as late as possible)

 

How long does the unfolding process take anyway, do we know that?

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DocM

Unfolding takes a few seconds.

The timing should be sometime after it goes subsonic, likely near terminal velocity which should be ~300+ kph.

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flyingskippy

I would think it depends on where they decide to lower the legs. Atmospheric drag would slow down the process. Deploying them early they would act as fins to stabilize the descent and possibly prevent spinning. Although if I remember what I learned in my aerodynamics class they would have to have to fight to keep the rocket flying engines first cause the added drag would have a tendency to cause the rocket to rotate to flying separation end first. There sure are a lot of questions with this launch!

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DocM

The landing burn will occur quite low down because the thrust to weight will likely be >1 or close to it, as it was with Grasshopper.

If you start the landing burn too soon the stage decelerates to a stop and rises again. If too late it hits hard. The idea is to have v=0 just as it touches down then cut the engine. SpaceX calls it a hoverslam landing, and Grasshopper perfected it.

In the midst of this for a ground landing is a divert maneuver. The first target point would be offshore so a commit decision can be made. If OK it diverts over land and sets down.

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flyingskippy

I assume they are still planning on decelerating with three engines then moving to one for touchdown? What is the lowest Throttle setting the Merlin can still run?

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DocM

3 engines for boostback & reentry, one for landing.

The official throttle range of M1D is. 70-100% with a s/l thrust of 147 klbf, but Musk recently stated that they've only been using it at 85% capacity and its real max thrust is significantly higher.

This may explain why the NASA NLS II mission calculator shows F9 v1.1 with a max expendable payload of over 16 tonnes vs the lower number on their website.

This all begs the question of just what the fully throttled down thrust level is, and if they've also been sandbagging the throttle range.

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flyingskippy

F9_4_Legs.jpgF9_4_Legs_flipped.jpg

I wonder if they plan on adding a fairing where the foot of the leg meets the core. I was looking at the rendition of the F9 with legs and it looks more streamlined in that area than it does in the photo.

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DocM

A fairing will be placed at the leg foot (top). If you look at the bench to the far left of the core you can see one of them.

The lower attachments have been there on all previous flights because they're part of the Octaweb so they work, and the legs have had wind tunnel tests.

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  • 4 weeks later...
DocM

F9R Dev-1 static fire, AND they now have an FAA permit for flight tests at McGregor, Texas.

There will probably only be a few flights at McGregor before moving F9R Dev-1 to the commercial SpacePort America in New Mexico for high altitude & hypersonic tests. SPA is near the White Sands Missile Range.

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DocM

F9R Static Fire

Published on Mar 28, 2014

SpaceX successfully test fired the first stage of F9R?an advanced prototype for the world's first reusable rocket?in preparation for its first test flight in the coming weeks. Unlike airplanes, a rocket's thrust increases with altitude; F9R generates just over a million pounds of thrust at sea level but gets up to 1.5 million pounds of thrust in the vacuum of space.

The F9R testing program is the next step towards reusability following completion of the Grasshopper program last year. Future testing, including that in New Mexico, will be conducted using the first stage of a Falcon 9 Reusable (F9R) as shown here, which is essentially a Falcon 9 v1.1 first stage with legs. F9R test flights in New Mexico will allow us to test at higher altitudes than we are permitted for at our test site in Texas, to do more with unpowered guidance and to prove out landing cases that are more-flight like.

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DocM

The F9R Dev-1's pad obviously has 2 zones; a launch fixture and a landing zone. F9R Dev-1 left, Grasshopper right.

jene3a7e.jpg

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  • 3 weeks later...
DocM

F9R Dev-1 FLIES!!

Which means it must have landed on those previously untested legs.

We should get a video soon.

http://m.wacotrib.com/blogs/joe_science/grasshopper-s-successor-flies-at-spacex-s-mcgregor-site/article_66310240-c67f-11e3-bf29-001a4bcf887a.html?mode=jqm

Grasshopper's successor flies at SpaceX's McGregor site

Reports have been confirmed that SpaceX's Falcon 9-R development vehicle made its first free flight today at McGregor taking off, hovering, moving sideways and landing. I've seen video of it (though it turns out that video wasn't supposed to be made public yet and is no longer available).

SpaceX McGregor will be testing the rocket the three-engine successor to the single-engine Grasshopper at lower altitudes before sending it to Spaceport America in New Mexico for higher (and farther) flights.

The eventual idea is to have a rocket stage that can return to its launch site for re-use, rather than burning up on re-entry. SpaceX hopes to test different parts of that capability after a launch of the full nine-engine Falcon 9 from Cape Canaveral, Fla., set for 2:25 p.m. CDT Friday (though the forecast is still iffy only a 40 percent of acceptable weather, rising to 60 percent for a Saturday attempt and 80 percent for a Tuesday launch).

After the Falcon 9's second stage sends the Dragon cargo ship on its way to the International Space Station, the first stage is planned to fire three of its nine engines for a controlled, non-burning-up descent from orbit, then fire one engine just before an Atlantic Ocean splashdown so it can drop into the water with minimal damage (a test over water means no one gets hurt if anything goes wrong, and SpaceX only gives about a 40 percent chance that the test will fully succeed).

The one time they tried this before, in a September launch from Vandenberg Air Force Base in California, they got the stage most of the way home before it spun out of control. The landing legs added to the Falcon 9 this go-round are hoped to help stabilize the rocket during splashdown.

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DocM

SHE RISES!!

Yes the legs get toasty, but they're coated with a thermal protection material like what Dragon wears.

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DocM

Elon Musk at the CRS-3 presser talked of there being an F9R Dev-1 and an F9R Dev-2, one for McGregor (flights to 10,000 ft) and the other for SpacePort America (flights to 300,000+ ft.)

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DocM

Good AvWeek article on the CRS-3 landing test, but this stood out.

Sounds like F9R Dev-2 will be flying high at SPA quite soon - up to >300,000 feet.

http://aviationweek.com/space/spacex-plans-multiple-reusable-booster-tests

>

.... further work is planned using the F9R Dev 1 in Texas in addition to a second F9R Dev 2, which will fly at SpaceX?s recently completed site at Spaceport America in New Mexico.

>

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DocM

http://m.wacotrib.com/blogs/joe_science/spacex-s-grasshopper-successor-flies-again/article_20161aaa-d18f-11e3-9a61-0019bb2963f4.html?mode=jqm

SpaceX's Grasshopper successor flies again

I finally got to see one.

SpaceX's F9R Dev ? the modified Falcon 9 first stage that's a bigger sibling to SpaceX's Grasshopper testbed rocket ? flew a second time Thursday at the company's McGregor development facility, two weeks after its first free flight.

The test is another step in SpaceX's drive to produce a recoverable and reusable first stage, which saw another leap forward with the successful splashdown of the actual Falcon 9 first stage after it launched the Dragon cargo ship toward the International Space Station.

I can't get much more specific because SpaceX hasn't talked about the test yet (that usually happens after a day or two). As near as I could tell it flew to the same 800-foot height that it did two weeks ago, and took the same type of course: up, hover, move sideways, land.

More as I get it.

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Beittil

I just saw the video... amazing! Bold and amazing! Within 2 weeks 4 times the height of the first flight and even higher then Grasshopper ever did. WOW :D

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DocM

WOW!!

1,000 meters, 4x as high as last time. Dev-1 is a sporty lady :)

Confirmed: Merlin 1D can throttle down to 40% - per Elon Musk.

Early flights of F9R will take off with legs fixed in the down position. However, we will soon be transitioning to liftoff with legs stowed against the side of the rocket and then extending them just before landing.

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watkinsx2

Thats some progress in two weeks!

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DocM

They'll try another sea landing May 10 after the ORBCOMM launch.

The Raptor engime reveal is May 17, Dragon Mk 2 is revealed on May 29, and rumors are there may be a second F9 launch in May.

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Beittil

Huh, whichone would that be? AsiaSat 8 pulled forward?

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DocM

Still working on it but maybe. Still iffy but it was up for June. Seems they're trying to ramp up the launch rate.

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