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Author Topic: SpaceX (general discussion)  (Read 211931 times)

Offline FutureSpaceTourist

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SpaceX (general discussion)
« on: September 24, 2011, 04:10:28 pm »
Thanks to Clark Lindsey for posting a link to this FAA document: 

Draft Environmental Assessment for Issuing an Experimental Permit to SpaceX for Operation of the Grasshopper Vehicle at the McGregor Test Site, Texas - September 2011

and for pulling out the following extracts:

Quote from: http://www.hobbyspace.com/nucleus/index.php?itemid=32669#c
2.1.1 Grasshopper RLV
2.1.1.1 Description

The Grasshopper RLV consists of a Falcon 9 Stage 1 tank, a Merlin-1D engine, four steel landing legs, and a steel support structure. Carbon overwrapped pressure vessels (COPVs), which are filled with either nitrogen or helium, are attached to the support structure. The Merlin- 1D engine has a maximum thrust of 122,000 pounds. The overall height of the Grasshopper RLV is 106 feet, and the tank height is 85 feet.

The propellants used in the Grasshopper RLV include a highly refined kerosene fuel, called RP- 1, and liquid oxygen (LOX) as the oxidizer. The Grasshopper RLV has a maximum operational propellant load of approximately 6,900 gallons; however, the propellant loads for any one test would often be lower than the maximum propellant load. Even when the maximum propellant load is used, the majority of the propellant would remain unburned and would serve as ballast to keep the thrust-to-weight ratio low.

p.13:

SpaceX anticipates that the Grasshopper RLV program would require up to 3 years to complete. Therefore, the Proposed Action considers one new permit and two potential permit renewals

p.15:

The FAA/AST has assumed that SpaceX would conduct up to 70 annual suborbital launches of the Grasshopper RLV under an experimental permit at the McGregor test site. This estimation is a conservative number and considers potential multiple launches per day and potential launch failures.

To support the Grasshopper RLV operations, SpaceX proposes to construct a launch pad and additional support infrastructure at the McGregor test site

p.16:

2.1.1.3 Flight Profile (Takeoff, Flight, and Landing)
The Grasshopper test program expected to be conducted under an experimental permit would consist of three phases of test launches, which would be performed in the sequence detailed below. SpaceX would repeat tests under each phase as necessary until SpaceX is ready to proceed to the next phase. Multiple test launches could occur each day during daytime hours only, and would be consistent with SpaceX’s lease with the City of McGregor. For example, SpaceX is prohibited from conducting engine tests between the hours of 12:00 a.m. and 7:00 a.m. per SpaceX’s lease with the City of McGregor.

Launch Phases 1 and 2: Below-controlled-airspace VTVL
The goal of Phase 1 is to verify the Grasshopper RLV’s overall ability to perform a VTVL mission. During a Phase 1 test, the Grasshopper RLV would be launched and ascend to 240 feet AGL and then throttle down in order to descend, landing back on the pad approximately 45 seconds after liftoff. The Grasshopper RLV would stay below Class E Airspace (700 feet AGL). In Phase 2, there would be slightly less propellant loaded, a different thrust profile, and the maximum altitude would be increased to 670 feet, still below Class E Airspace. The mission duration during Phase 2 is again approximately 45 seconds.

Launch Phase 3: Controlled-airspace VTVL (maximum altitude)
The goal of Phase 3 is to verify the Grasshopper RLV’s ability to perform a VTVL mission at higher altitudes and higher ascent speeds and descent speeds. To achieve this, the maximum mission altitude would be increased from 670 feet incrementally up to 11,500 feet. The altitude test sequence likely would be 1,200 feet; 2,500 feet; 5,000 feet; 7,500 feet; and 11,500 feet. The maximum test duration would be approximately 160 seconds. The Grasshopper RLV would land back on the launch pad.

Offline Michel Van

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Re: SpaceX (general discussion)
« Reply #1 on: September 25, 2011, 01:15:35 am »
nice find, FutureSpaceTourist

but i wounder for Wat they need the Grasshopper RLV ?
they abandon the First stage recuperation on Falcon 1 and 9 series

so is this test for rocket decent landing, for a Lunar or Mars lander stage ?
or is SpaceX testing for SSTO as replacement for Falcon 1 series ?

 
I love Strange Technology

Offline FutureSpaceTourist

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Re: SpaceX (general discussion)
« Reply #2 on: September 29, 2011, 11:13:00 am »
SpaceX has now released more details of their RLV plans as part of Elon Musk's talk today at the National Press Club: http://www.spacex.com/npc-luncheon-elon-musk.php

The following animation shows a fully-reusable version of a Falcon 9. The first stage appears to use its engines to slow its descent (no obvious heat shield) before making a powered vertical landing. The second stage orients itself so that it re-enters top first with a heat shield before again making a powered vertical landing.



I've seen a quote attributed to Elon Musk saying that on paper they believe the RLV numbers close and that Grasshopper is part of establishing whether or not that's true in practice. He also said it's an approach he's had in mind for some time (I assume years).
« Last Edit: September 29, 2011, 11:17:43 am by FutureSpaceTourist »

Offline Archibald

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Re: SpaceX (general discussion)
« Reply #3 on: September 29, 2011, 11:36:16 am »
The video is just amazing - 2001 made real ! The second stage reentry, heatshield first, reminds me of the Kistler K-1.
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Offline Orionblamblam

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Re: SpaceX (general discussion)
« Reply #4 on: September 29, 2011, 12:15:53 pm »
  He also said it's an approach he's had in mind for some time (I assume years).

It's an old, old scheme. Chrysler proposed a similar system for Mercury-Redstone, to make a cheap astronaut trainer. And there's the Douglas SASSTO and reusable S-IVB concepts.

I love it!
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Offline flanker

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Re: SpaceX (general discussion)
« Reply #5 on: September 29, 2011, 02:08:04 pm »
That looks very sci-fi.  ???

I can't imagine it is effective payload wise, as it has to carry plenty of fuel to make a controlled decent the way it does. Has anything like this been done in real life?
Push the envelope,watch it bend.

Offline FutureSpaceTourist

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Re: SpaceX (general discussion)
« Reply #6 on: September 29, 2011, 09:39:07 pm »
In terms of payload I wonder whether new versions of the Merlin engine, which would enable increased payload, are key to carrying the extra fuel, landing gear etc ? The Merlin 1D can also be throttled.

When Elon says the numbers close (in theory) I guess there must be an acceptable customer payload left!

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Re: SpaceX (general discussion)
« Reply #7 on: August 28, 2012, 07:03:28 am »
Elon Musk on SpaceX’s Reusable Rocket Plans.
SpaceX is hard at work trying to design rocket parts that can fly themselves back to the launchpad for reuse. We talked to founder Elon Musk about how far the company’s designs have come.
February 7, 2012 6:00 PM
By Rand Simberg
Quote
The key, at least for the first stage, is the difference in speed. "It really comes down to what the staging Mach number would be," Musk says, referencing the speed the rocket would be traveling at separation. "For an expendable Falcon 9 rocket, that is around Mach 10. For a reusable Falcon 9, it is around Mach 6, depending on the mission." For the reusable version, the rocket must be traveling at a slower speed at separation because the burn must end early, preserving enough propellant to let the rocket fly back and land vertically. This also makes recovery easier because entry velocities are slower.
However, the slower speed also means that the upper stage of the Falcon rocket must supply more of the velocity needed to get to orbit, and that significantly reduces how much payload the rocket can lift into orbit. "The payload penalty for full and fast reusability versus an expendable version is roughly 40 percent," Musk says. "[But] propellant cost is less than 0.4 percent of the total flight cost. Even taking into account the payload reduction for reusability, the improvement is therefore theoretically over a hundred times."
http://www.popularmechanics.com/science/space/rockets/elon-musk-on-spacexs-reusable-rocket-plans-6653023

 For the current version of the Falcon 9 with a 10,000 kg capability to LEO was made reusabe, this would mean its payload is reduced to 6,000 kg. According to SpaceX though the price per kilo would reduce because it would be reused.
 SpaceX though is moving to a larger version the Falcon 9 v1.1. On its website SpaceX now gives the specifications for the new Falcon 9 version:

http://www.spacex.com/falcon9.php

 The new version will have a payload capability of 13,150 kg to LEO. Oddly though, it still gives on that page the price for the current F9, $54 million. I don't know if they mean to keep the price the same for the larger version or not.
 The reusability would come into play when the new version is in use; so assuming a 40% payload reduction, the payload to LEO for the reusable F9 v1.1 would be 7,890 kg.
 The key question is of reusability of the engines. Can SpaceX make them reusable at low cost? While watching the retrospectives on Neil Armstrong on NASA TV, they show images of him as a X-15 pilot. This reminded me we actually had reusable rocket engines from the very earliest days of manned rocket-powered flight. The XLR-99 engine used on the X-15 was reusable for 20 to 40 times before overhaul, after which it could be reused again:

XLR-99.
http://www.astronautix.com/engines/xlr99.htm

 The 3 copies of the X-15 aircraft flew for a total of 199 flights. Can you imagine how expensive that program would have been if an entire new X-15 aircraft had to be used for each flight?

  Bob Clark

 

Offline FutureSpaceTourist

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Re: SpaceX (general discussion)
« Reply #8 on: September 10, 2012, 11:22:19 pm »
Some nice photos of grasshopper at: http://www.flickr.com/photos/jurvetson/7971310054/in/set-5956/. It's big!

Looks like they're getting ready to fly it soon?

Offline cluttonfred

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Re: SpaceX (general discussion)
« Reply #9 on: September 11, 2012, 07:11:16 am »
Beautiful stuff, but perhaps someone can educate me.  Why the desire for powered vertical landing for all stages?  Wouldn't some kind of parachute make more sense in terms of weight, perhaps small drogues for initial deceleration and descent and a paraglider for controlled landing at a particular point?  While emininetly cool and obviously a factor in simplifying operations, I just don't see the essential advantage of powered descent over a parachute/steerable paraglider typle operation.  It also seems very creepy for manned operation--presumably there would be some sort of backup parachute?
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Offline Hobbes

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Re: SpaceX (general discussion)
« Reply #10 on: September 11, 2012, 07:23:29 am »
The objective is a soft landing with minimal work to be done to reuse the stage. If you use a parachute, you still need a rocket engine to provide a soft landing on land. You could splash it into the ocean, but then you'd have seawater everywhere (i.e. you'll need to disassemble and clean everything) and the splashdown might damage the engines.

Offline cluttonfred

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Re: SpaceX (general discussion)
« Reply #11 on: September 12, 2012, 01:21:41 am »
Thanks for the reply, but I am still not sure I buy it.  Retractable wheels or skids could allow soft landing on a runway (in a horizontal attitude, of course).  You could even imagine a football-field-size inflatable mattress (think stuntmen or the experiments with rubber decks for aircraft carriers) or a large net (think small UAV recovery) as alternatives.  I just don't see how the "balancing on a bowling ball" technical challenge and the need to carry so much extra fuel are really justified.
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Offline greedo

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Re: SpaceX (general discussion)
« Reply #12 on: September 12, 2012, 11:18:21 am »
@Mole


Think of it in terms of working with the engineering and technology required for landing on Mars, and it fits with Musk's long term goals.

Offline Hobbes

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Re: SpaceX (general discussion)
« Reply #13 on: September 12, 2012, 11:56:02 am »
A horizontal landing would mean strengthening the fuselage which eats into the payload margin.

I'm sure they've done the calculations to compare the weight impact of parachutes vs. powered landing.

Offline RanulfC

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Re: SpaceX (general discussion)
« Reply #14 on: September 13, 2012, 07:05:29 am »
Beautiful stuff, but perhaps someone can educate me.  Why the desire for powered vertical landing for all stages?  Wouldn't some kind of parachute make more sense in terms of weight, perhaps small drogues for initial deceleration and descent and a paraglider for controlled landing at a particular point?  While emininetly cool and obviously a factor in simplifying operations, I just don't see the essential advantage of powered descent over a parachute/steerable paraglider typle operation.  It also seems very creepy for manned operation--presumably there would be some sort of backup parachute?
Work has shown that the actual mass difference between parachutes and powered landing are very similar. Keeping in mind the added mass for steerable para-chute/glider, control system and added vehicle mass for strengthing to accomodate the new loads. (On average a steerable para-chute/glider system masses around 1.5 to 2.0 times that of a "standard" canopy)
 
Further, a powerd landing allows a "zero-zero" touchdown where doing so with a parachute is more difficult, especially in any type of surface winds.
 
We also need to keep in mind that Space-X is currently using "parachutes" for recovery but hasn't gotten a stage to reenter intact :)
 
The Super-Draco abort/landing system will continue to fly a "back-up" parachute capable of landing the Dragon capsule itself until Space-X feels confident enough in the system to pull it.
 
Thanks for the reply, but I am still not sure I buy it.
You didn't, Musk did  ;)
 
Seriously, they have done the "math" here and feel that a powered landing makes better operational and economic sense than and unpowered landing.
 
Quote
Retractable wheels or skids could allow soft landing on a runway (in a horizontal attitude, of course).  You could even imagine a football-field-size inflatable mattress (think stuntmen or the experiments with rubber decks for aircraft carriers) or a large net (think small UAV recovery) as alternatives.  I just don't see how the "balancing on a bowling ball" technical challenge and the need to carry so much extra fuel are really justified.
Let me expand a bit on what I said earlier vis-a-vis the alternatives.
 
First of all you need to take into consideration that they are planning on using "boost-back" in the flight plan. This means the (one or multiples) rockets are going to be used to slow the first stage down and boost it back towards the launch site. This is going to reduce the control and reentry issues for the booster stage significantly and since you're already planning on multiple restarts and enhanced throttleability it makes more sense to trade in parachutes for propellant mass for a controlled landing.
 
Secondly a powered landing approach and landing zones is much smaller as the lander is considered much more "under-control" than a parachute/para-wing run in to landing. Recall that with a Falcon-9-Heavy at least two of the boosters will be landing within seconds of each other, while this is done (horizontally) in rapid sequence at any airport this also assumes a tightly controlled sequence of events (pilot/ground-control) AND a self-powered (jet-engines) vehicle capable of "clearing" the runway for the next flight all by itself. Imagine having to have a ground-crew trying to hook up to and tow a recently landed booster stage with a second one already on final approach :)
 
And that "assumes" a horizontal landing which as noted would require much more modification and mass for "dual" axis (vertical/horizontal) operations! Also keep in mind that the stage WANTS to be "vertical" because of the mass of the engines at one end. This would tend to especially impact (no pun intended) horizontal parachute/para-wing landing as the CG/CB is so far aft on the booster and where the attachement points and line-control components would have to be located.
 
The idea(s) of a huge airbag and soft surfaced landing pad would be unworkable from an operational stand point as well. These still impose large "side/horizontal" landing loads on the vehicle even if they work perfectly and the booster guidance system works nominally. (I'll say the largest "UAV" I've seen use an airbag was a cruise missile and it required a mid-air snatch by a helicopter to achieve the needed accuracy to land exactly on the bag. A couple of feet to either side and it would roll as the bag deflated and be wrecked. Now imagine trying to do this with parachutes and a 90' tall booster rocket :) )
 
So the booster would have to STILL be heavily modifed to resist the loads of any of the suggested methods and even then... Well, take a cardboard tube, wrap it in aluminum foil, (to represent the rockets "skin" surface) then attach a weight to one end and drop it on a pillow or foam pad from a couple inches up a half-dozen times. Every wrinkle and dent in the foil is a possible point of damage in the tankage of the booster, every time it lands on or partially on the "weight" the full mass of the empty booster just "touched-down" on a single engine bell and/or it's control system. You begin to see the maintenance nightmare this would be.
 
Vertical powered touch down allows precise control descent and landing in the same orientation and along the same stress lines as the original vertical take off. Landing legs absorb any final energy and prevent the booster from falling over or damaging the vulnerable tanks and engines. Finally the whole "balancing-on-a-bowlingball" act has been shown to be a pretty much a whole lot easier and controlable that many people assumed it was. From the Lunar Module, thru the DC-X/Xa to the number of small company VTVL experiments has pretty conclusivly shown that its simply NOT the "issue" many people thought it was. The advantages of vertical landing toward reaching simple "gas-and-go" operations are numerous enough to outweigh (sorry again no pun intended) the payload hit(s) of propllant equipment mass to do it.
 
IMHO if you seriously do the "trades" on it and run some basic BOTE calculations I think it really tends to show the truth that Spacecraft are NOT Airplanes and Airplanes are NOT Spacecraft...
 
Randy