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#226 2019-03-01 20:07:58

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
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Re: Starship is Go...

SpaceNut wrote:

Knowing that interplanetary speed is the issue for a ship having not enough fuel to slow, then what else can we do?

What do you want? You could use aerocapture: skim the atmosphere to slow enough to enter orbit. Then aerobrake: skim the atmosphere in successive orbits to slow further, dropping orbit. Then when you have bled off enough energy, enter the atmosphere. That can be tricky because the upper atmosphere is dynamic. X-15 had a flight where it flew horizontally out of the atmosphere. It flew high in some sort of plume, flew horizontally out of the plume into vacuum. X-15 used control surfaces for orientation, so once it was out of the atmosphere, the pilot no longer had control. He had to throttle down the rocket engine, wait until he fell back into atmosphere so he could regain control. So if you want to come in at interplanetary speed, exactly how deep into the atmosphere do you go to get just the right amount of drag? Not enough, you fly off at escape velocity into solar orbit. Too much and you overwhelm your heat shield. Then there's the issue of skip; the Soviets tried to deliberately skip Zond 4 upon returning from the Moon. They wanted to slow in a skip, then enter to land on the steps of Kazakhstan. This was an unmanned mission, capsule was a modified Soyuz called 7K-L1. The skip didn't work, it went in, splashing down in the Indian Ocean. NASA analysis said if a Cosmonaut had been onboard, it would have been a rough ride but he would have survived.

The greatest issue with aerocapture or aerobraking at Earth is missing all the satellites. Do you realize how many satellites orbit Earth today? I would love to do this. I have posted a mission plan that uses a fabric heat shield similar to ADEPT to aerocapture into Earth orbit, then rendezvous with ISS. My idea was to use Nextel 440 fabric instead of carbon fibre fibric. Carbon fibre can handle more heat, but can it handle more than one atmospheric entry? Nextel 440 was selected by Ames Research Centre for DurAFRSI, an advanced thermal blanket for the "next" shuttle. The greatest issue is whether you can avoid all those satellites. We could put a matrix of weather satellites in Earth orbit to measure the upper atmosphere. Then calculate exact trajectory for aerocapture. Tricky, but possible.

Last edited by RobertDyck (2019-03-01 20:08:54)

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#227 2019-03-02 16:59:09

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 15,587

Re: Starship is Go...

I think the return direct trip from mars answer you have hinted at RobertDyck. The prelaunch from mars would have the crew affixing a very large ADEPT fabric unit to the top of the BFR nose with the control and bracing pieces wired for use upon nearing earth where it would be unfurled for use to aerocapture the bfr into orbit there by saving the fuel which it still has for the landing on earth.
This also saves the pica shield for its one final use with the ADEPT unit if we are still able to use it.

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#228 2019-03-02 20:07:37

kbd512
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Registered: 2015-01-02
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Re: Starship is Go...

Robert,

I don't see the purpose of sending Starship all the way back to Earth.  Starship is supposed to be a rocket with airliner-like reusability.  No airline service in existence uses their expensive airliners once every two years.  It's just not economical to do that.  Once you get something to Mars, you repair or refurbish it on Mars until it's time for depot level maintenance.  Then and only then do you send it back to Earth or use the downed vehicle for spare parts.  That's how the military does it and that's how airline services do it.  This is about spending money to do useful things, not spending money for the sake of spending money.

My BFS / Starship applications sticky / diatribe was entirely about using BFR and BFS / Starship components to construct purpose-built tools that are mass-optimized and functionality-optimized for specific tasks.  Any attempt to create a be-all / end-all platform is what causes cost to achieve escape velocity.  That's the exact opposite of how to run an economical space transport business.  The Starships are short-haul vehicles.  The Bigelow Aerospace inflatables are long-duration space flight habitats built for that specific purpose.

There is no reason why SpaceX can't have BA build an inflatable ring habitat module that provides Mars AG for the transit.  This habitat would be attached to a propulsion system.  That system could be chemical or electric, but the point is that the mass transport vehicle never reenters and establishes stable orbits.  I would think that since we're going back to the moon first, which came directly from Elon Musk's mouth while NASA Administrator Bridenstine was sitting next to him during the Spx-DM1 press conference, that this vehicle would be assembled in lunar orbit.

Even if people here are against the idea of using electric propulsion, someone here must understand the mass efficiency of not lugging oversized fuel tanks and over-sized rocket engines to and from Earth, simply because that additional hardware is required to insert a payload into orbit whenever it's used to get into orbit.  A complete lunar and Mars solution involves more than one type of vehicle.  Yes, the rocket is required to get payloads into orbit and is a very important "first step" to going anywhere, but after that more suitable solutions are required.

Living in the rocket is a non-starter.  People don't live mere feet from operating cryogen plants.  It's just not a good idea.  That's why it's never been done on Earth.

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#229 2019-03-02 20:18:13

SpaceNut
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Re: Starship is Go...

So how well would the bigelow doughnut do with a return inter planetary trip speed?

That would mean going much slower like in ion drive speed and breaking all the way here with that gentle slowing engine so as to not need the heat shielding as there would be a gravitation capture to orbit.

That means using 1 bfr to get to orbit coming back empty once unloading into the transport habitat and on the other end awaits another bfr to transport the human cargo to the planet.

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#230 2019-03-02 20:30:11

kbd512
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Re: Starship is Go...

SpaceNut,

The ion thruster doesn't have to do 100% of the work required.  We can still use chemical rockets for impulse maneuvers.  This all or nothing notion of how this would work is the wrong way to think about the problem.  The solution is to use both.  After you get shot off to wherever you're headed with the chemical rocket, you can use ion thruster on the back end to slow for the orbital insertion.  If you brake just a little to soon or too late with the chemical rocket, you're screwed.  If you have electric for the insertions, you can employ an energy management scheme that can adjust, within limits, to the fudge factors involved with the navigation.  Mid-course corrections can also be done with the ion thrusters.  The ion thrusters can also add more speed.  The chemical rocket is just to get you on your way.  After that, the electric cruise propulsion system takes over.

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#231 2019-03-02 20:43:42

Oldfart1939
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Registered: 2016-11-26
Posts: 1,598

Re: Starship is Go...

The eclectic solution proposed by kbd512 certainly has merit. The current concept of using the Starship in the role proposed by Musk seems to originate in the "one size fits all" school. My issue with ion propulsion is source of necessary power. Solar panels--if enough of them are used can provide power, but the more power available the more thrust becomes available. A nuke powerplant could provide what's needed. Some creative thinking will be required in order to satisfy the shielding requirements--and associated mass.

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#232 2019-03-02 21:58:18

SpaceNut
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From: New Hampshire
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Posts: 15,587

Re: Starship is Go...

We have been saying for quite some time that even the same thing holds true for the lunar plans of Nasa with the SLS and BFR is not any different to what we want to have as the goal. It will take many more parts to make the moon missions happen and it will not change for mars just the size will as durations of flight make that first and then radiation and gravity cause the next 2 elements of the plan to grow even larger.

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#233 2019-03-03 12:00:05

GW Johnson
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From: McGregor, Texas USA
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Posts: 3,523
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Re: Starship is Go...

For RobertDyck re: post 226 above.

Like its predecessors,  the X-15 had aerodynamic control surfaces.  Unlike them,  it also had attitude thrusters,  because its designers knew it would fly into effective vacuum.  Initially,  these were hydrogen peroxide decomposition thrusters.  I don't remember if that was updated to something else later in the program.

The predecessors (X-1 series,  X-2,  D-558-2) never flew high enough to need attitude thrusters,  although the X-2 came close enough that it killed a pilot until they enlarged its vertical fin. 

One descendant of this series of experimental rocket planes was the NF-104,  which was an F-104 modified with two rocket engines at the base of its vertical fin.  These enabled it to ballistically zoom nearly to space,  far outside the normal flight envelope.  It also had attitude thrusters.  It was intended to train USAF astronauts,  in a program completely separate from NASA's astronaut program.

Chuck Yeager's crash of the NF-104 was due,  he claimed,  to the failure of those thrusters at about 100 kft to put the nose down for entry,  on the second flight he made that day.  This was the bailout incident with the helmet fire that burned Yeager so badly. 

The one fatal crash of the X-15 was laid to its attitude thrusters failing to put the nose down on that flight.  In both cases,  the vehicles reentered sensible atmosphere very nearly tail-first.  The F-104 tumbled out of control with no hydraulics for the controls,  because the engine spooled down to zero;  the X-15 broke up in midair from broadside air loads (flying quite a bit faster). 

The fatal X-2 flight was entirely aerodynamic-surface controlled,  at about 70 kft (remarkable for the time).  Most sources claim the smaller vertical fin was too immersed in the fuselage boundary layer to have sufficient effectiveness in such thin air.  A part of the problem was disobeying orders:  the pilot attempted a turn in otherwise level Mach 3 flight at 70 kft,  in spite of orders not to do so.  With the larger fin,  the loss of control in high-altitude turns never happened again.

Just as an aside,  the Douglas D-558-2 did not feature an all-moving horizontal tail the way the Bell X-1 and X-2 did.  Once supersonic,  the elevators were completely ineffective.  The pilots flew that bird to Mach 2.5 and some rather high altitudes using the trim wheel for pitch control.  Douglas test pilot Bill Bridgeman flew it that way to Mach 1.98,  before they turned it over to the Navy for Scotty Crossfield to take it to Mach 2 and beyond.

Like all such pilots,  Crossfield had to train himself from Mach 1-ish up,  before hitting Mach 2. All of these birds were single-seat.  No trainers.

As a boy,  it was stuff like that I heard about on the news for some years,   until North American rolled out the X-15 (and NASA got created) in 1958. 

GW

Last edited by GW Johnson (2019-03-03 12:06:38)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#234 2019-03-08 12:06:00

louis
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From: UK
Registered: 2008-03-24
Posts: 4,633

Re: Starship is Go...

Starship Hopper is being moved to launch pad at Boca Chica! smile

https://www.youtube.com/watch?v=qIFpLblpC-E


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#235 2019-03-14 06:53:17

louis
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From: UK
Registered: 2008-03-24
Posts: 4,633

Re: Starship is Go...

Latest Cloudlicker video:

https://www.youtube.com/watch?v=s_sR6V5CC3M

Star Hopper on the launch pad.  Single Raptor engine to be installed for first test? A second, larger Star Hopper seems to be in preparation.

And a Curious Elephant video...more a recap of how we got to where we (or Space X) are. 

https://www.youtube.com/watch?v=O_c5fnTypDo


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#236 2019-03-17 18:11:14

Void
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Registered: 2011-12-29
Posts: 3,011

Re: Starship is Go...

https://www.cnet.com/news/elon-musk-sho … ield-test/
Quote:

Elon Musk shows off fiery SpaceX Starship heatshield test
Feeling hot, hot, hot.

So, puzzled.  Tiles.  Not active cooling?  GW>>>Pica???

Well, maybe SpaceX has something new.  However, they decided to stick with cold gas thrusters, in order to get Starship up and running ASAP, so maybe for heat shield, they will shelve active cooling and go with a more tried and true method as well, to get the Starship into reality?

Frankly I was a bit scared of the active cooling anyway.  A NASA person reasoned that a bird turd on Earth or dust on Mars could plug the pores, and I suppose a hole might burn into the heat shield.

I had a flaky notion of a possible fix for that, (Put an ablative under the perforated stainless steel, as an emergency heat shield), but...I think it appears that Pica would not be that compatible with a fluid, such as water or Methane.

So, really if I interpret this correctly it is Hex tiles, of Pica?  Maybe.  But as I said, I think they will go the shortest route possible to make Starship real.  Maybe they experiment with active cooling later on later un-crewed versions.

Done

Last edited by Void (2019-03-17 18:19:36)


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#237 2019-03-18 12:25:22

Void
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Registered: 2011-12-29
Posts: 3,011

Re: Starship is Go...

Now I feel much more comfortable with the Starship heatshield plans.

https://www.engadget.com/2019/03/18/spa … t-shields/

Turns out nobody was entirely wrong.  It seems that there will be at least 3 methods.
1) Leeward side of the ship, stainless steel is all that is needed.
2) At first, all of the windward side, Hexagonal Tiles.  (I think, all of the windward side).
3) Then only where the Hexagonal tiles erode they will implement some kind of active cooling.

The tiles will be Hexagonal so that hot gasses cannot follow a strait channel to erode between the tiles.

If I understand this correctly, then even if the active cooling fails somewhere, the ablative heat shielding will hopefully save the day.  The only loss if this is true, would be that they have to repair the heatshield tiles at that location, and also I presume fix the active cooling. Of course this is my speculative impression of what they might be up to.  Perhaps there will be more surprises instead.

This then also indicates that since only special areas of the ship will have active cooling, the mass of the active coolant can be kept down.

I do like it.  Not 100% sure that I have it as they will actually do it, but anxieties are much reduced in my mind.

Down the road, I am going to expect that not only will Oxygen come from the Moon for Starship to re-propellant with, but also perhaps water for reentry cooling.  Being able to re-tank Oxygen in LEO, and also @~somewhere near the Moon, and to load water perhaps for coolant for atmospheric entry to Mars will really make a difference I am thinking.  And an article I have seen can be true, where under those circumstances Starship could make a transit Earth>Mars in 30-40 days, that will really break open a new space age.

Done.

Last edited by Void (2019-03-18 12:34:49)


I like people who criticize angels dancing on a pinhead.  I also like it when angels dance on my pinhead.

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#238 2019-03-18 14:31:32

kbd512
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Registered: 2015-01-02
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Re: Starship is Go...

That seems fairly sensible and reasonable, but there's only one sure-fire way to determine which tiles will be damaged and that results of the test could be rather expensive if all doesn't go according to plan.  Anyway, it's good to know that that aspect of the design has been sorted out.

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#239 2019-03-18 15:07:23

louis
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From: UK
Registered: 2008-03-24
Posts: 4,633

Re: Starship is Go...

Tiles. So how do they do the maintenance on the first Starship on Mars if tiles need replacing? This doesn't sound good to me.

Wouldn't they need some big infrastructure?

Void wrote:

Now I feel much more comfortable with the Starship heatshield plans.

https://www.engadget.com/2019/03/18/spa … t-shields/

Turns out nobody was entirely wrong.  It seems that there will be at least 3 methods.
1) Leeward side of the ship, stainless steel is all that is needed.
2) At first, all of the windward side, Hexagonal Tiles.  (I think, all of the windward side).
3) Then only where the Hexagonal tiles erode they will implement some kind of active cooling.

The tiles will be Hexagonal so that hot gasses cannot follow a strait channel to erode between the tiles.

If I understand this correctly, then even if the active cooling fails somewhere, the ablative heat shielding will hopefully save the day.  The only loss if this is true, would be that they have to repair the heatshield tiles at that location, and also I presume fix the active cooling. Of course this is my speculative impression of what they might be up to.  Perhaps there will be more surprises instead.

This then also indicates that since only special areas of the ship will have active cooling, the mass of the active coolant can be kept down.

I do like it.  Not 100% sure that I have it as they will actually do it, but anxieties are much reduced in my mind.

Down the road, I am going to expect that not only will Oxygen come from the Moon for Starship to re-propellant with, but also perhaps water for reentry cooling.  Being able to re-tank Oxygen in LEO, and also @~somewhere near the Moon, and to load water perhaps for coolant for atmospheric entry to Mars will really make a difference I am thinking.  And an article I have seen can be true, where under those circumstances Starship could make a transit Earth>Mars in 30-40 days, that will really break open a new space age.

Done.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#240 2019-03-19 07:43:37

Void
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Registered: 2011-12-29
Posts: 3,011

Re: Starship is Go...

Well Louis, as I interpret what was presented, they will use the Hex tiles, and then study the erosion on them.  They seem to want zero erosion.  So, they will somehow, (Method not strongly defined), add active cooling where erosion occurs with the objective of eliminating erosion.

That article indicates that they want to be able to fly the Starship again the same day it lands.  So, the focus must be on Earth<>LEO & Earth<>Moon, as a couple of extra days downtime in a Mars trip can't be nearly as significant.


The vast majority of launches have to be not directly for Mars.  Satellites, Moon activities, Space Station stuff?, Refueling for the Moon and Mars, and then finally on occasion a trip to Mars.  Dr. Zurbin has mentioned that tying up a Starship for Mars is expensive, as it could have been used to launch a bunch of stuff to LEO and beyond during a Mars trip/habitat use.

I think that rather quickly using Starship to go to Mars will be replaced with dedicated advanced propulsion interplanetary craft, Ion, Fusion, Fission (Russia?), and ???? Something else?

My impression is that the tiles are not like space shuttle tiles.  And of course we think they are far less likely to incur impact damage to the tiles.  So, frankly, I would not be surprised if a early ship to Mars did not even have active cooling at all.  I have to imagine that they will first experiment with it on non-crewed ships.  To me that makes sense.

And that is the best I can do, from what I think I know at this time.  A fair amount of guessing as well.

GW was quite right it seems, but then active cooling in a more limited way is on the horizon, it would seem.

And the Moon is getting bigger and bigger.  Also, meshing with NASA plans for the Moon seems to be getting bigger and bigger.


Done.

Last edited by Void (2019-03-19 07:54:16)


I like people who criticize angels dancing on a pinhead.  I also like it when angels dance on my pinhead.

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#241 2019-03-19 08:31:49

kbd512
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Registered: 2015-01-02
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Re: Starship is Go...

SpaceX's PICA-X material and the 3D woven ablative materials created for NASA by Bally Ribbon Mills for Orion are fabricated in blocks, cut to shape with a saw, and then sanded to the desired dimensions.  The materials in question are roughly the same density as Balsa wood, so my guess would be that blocks or sheets of this material could be packed in the cargo bay of Starship and then used to replace badly damaged tiles.  This goes back to my assertion, based upon actual testing by NASA, that the outer mold line of the vehicle is important and that the charred material should be removed.  GW said that removal of the charred material is not required.  Maybe he's right, but how do you match the properties of a virgin piece of PICA replacement tile to one that's charred half-way through?

Anyway, I still favor the idea of using a robotic field tool to create a smooth ablative surface for the atmosphere to act upon during reentry at both ends of the transit.  That can be modeled and accounted for in the mathematics used for reentry.  An unevenly ablated surface, less so.  I'd be very leery of aerodynamic loads taking perfectly good chunks of PICA or whatever with it after the surface was partially used up during the Mars reentry event.  That could be a total non-issue, but it bothers me.  I also dislike the idea of char material floating around in the traffic lanes between Earth and Mars.  There's enough debris orbiting the Earth as is.  If minor heat shield refurbishment at both ends is a bridge too far, then what happens if a rocket engine needs maintenance?  The ability to perform field maintenance should be part of the equation used to determine when we're actually ready to go.

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#242 2019-03-19 11:53:33

GW Johnson
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From: McGregor, Texas USA
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Posts: 3,523
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Re: Starship is Go...

A reminder:  this BFS/Starship thing is first and foremost a freighter to and from low Earth orbit.  They will have considerable entry experience with it in that role before it goes anywhere else.  That experience will tell them what spare parts and replacement procedures they will need. 

As for char-removal-or-not,  one group of folks to ask would be the folks with actual experience testing ablative-lined ramjet combustors.  Few are left in the US,  although I am one of them.  For that application,  the change in internal mold line was small compared to basic dimensions,  and proved quite unimportant.  It looks rough to the eye,  but is not,  fluid mechanically. 

Some of us actually re-fired items in test,  as long as there was virgin underlying the char layer to hold it in place.  You do lose char as carbon dust,  basically.  Not a lot,  but some.  If a chunk comes loose,  that goes out the tailpipe in a condition resembling porous charcoal.

The people in the US who have real experience with this,  worked on things like ASALM-PTV,  ALVRJ,  and VDFR (ramjet for AMRAAM) about 20-40 years ago.  There are almost none today.  There is more recent experience with it in Russia and China,  and India,  plus in Europe,  all of whom are flying ablative-lined ramjets today.

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#243 2019-03-19 14:11:55

kbd512
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Registered: 2015-01-02
Posts: 2,834

Re: Starship is Go...

GW,

1. Does the ramjet example scale up to a Saturn V class upper stage reentering the atmosphere at 12km/s?

2. How big were the chunks that broke off that were subsequently sucked through the ram (dust, pebbles, charcoal briquettes, etc)?

3. If you char 40% of the PICA during the reentry at Mars, would there still be sufficient adhesion of the virgin material after months of thermal cycling from propellant batch loading and day/night cycles for it to stay put during the Earth reentry?

4. Does this problem / question become easier to solve if the vehicle stays at Mars and never makes another reentry at interplanetary velocity?

5. Is it easier to just send Starship into orbit to pick up / drop off subsequent batches of supplies and people and replace heat shield material or send Starship all the way back to Earth?

I would think it'd be lighter / faster / cheaper to just ship blocks of consumable PICA or whatever to Mars, one-way, but that's just me.

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#244 2019-03-19 16:53:21

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 3,523
Website

Re: Starship is Go...

Kbd512:

1. Does the ramjet example scale up to a Saturn V class upper stage reentering the atmosphere at 12km/s?  Good question.  I dunno.  The dynamic pressure inside the ramjet combustor near sea level was around 1000-2000 psf.  Gas temperatures were 4000-5000 F.  High pressure relative to atmospheric ,  subsonic flow near Mach number 0.42.

2. How big were the chunks that broke off that were subsequently sucked through the ram (dust, pebbles, charcoal briquettes, etc)?  The pieces were generally inch scale laterally or smaller,  and around 0.1 inch thick or less,  if char came loose from the virgin beneath.  These had less strength and density than a low-grade porous charcoal briquette.  Most of the erosion was shedding sand- or dust-like material,  continuously.  The material was an ablator made of PDMS polymer,  reinforced with carbon fibers,  silica powder,  and silicon carbide powder.   Intended to be one-shot for several minutes operation,  although I reused many fired cases in experimental work.  This stuff was about factor 10 more erosion-resistant than the usual solid rocket motor liner ablatives,  which were just fiber-reinforced rubber. 

3. If you char 40% of the PICA during the reentry at Mars, would there still be sufficient adhesion of the virgin material after months of thermal cycling from propellant batch loading and day/night cycles for it to stay put during the Earth reentry?  I don't know.  PICA-X is an ablative,  and supposedly one of the better ones.  Never used it in a missile,  because it was not yet available 25-45 years ago when I was doing ramjet and rocket work. 

4. Does this problem / question become easier to solve if the vehicle stays at Mars and never makes another reentry at interplanetary velocity?  All I know is what I read on Spacex's website in its varying incarnations over the last few years.  Supposedly it's good for one Mars entry (similar to an Earth LEO entry) plus one free-return Earth reentry from the interplanetary trajectory.  It's better than it needs to be to come home from the moon,  perhaps 2 flights.  Which means it ought to serve for about 4 reentries from LEO.

5. Is it easier to just send Starship into orbit to pick up / drop off subsequent batches of supplies and people and replace heat shield material or send Starship all the way back to Earth?  I think the idea was to send some BFS/Starships 1-way to Mars,  and then only some of them home again,  at least initially.  The heat shield should be good for that service,  based on what I read.  I don't know how it is bonded to whatever substrate in their designs.  That bondline would be the vulnerability for thermal cycling,  not the heat shield material itself. 

Repairs would be to glue a new tile wherever it was needed.  I know nothing about their glue.  It would have to work in near-vacuum conditions on Mars,  and for-sure-vacuum on the moon,  or in LEO.  But if you have such a glue,  there woulds seem to be little to stand in the way of making repairs in space.

GW

Last edited by GW Johnson (2019-03-19 16:55:35)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#245 2019-03-19 17:31:34

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 15,587

Re: Starship is Go...

Thats providing you inspect for the damage and get to where it is safely floating without losing the tools to do the work.

So do not use a pica x shield for mars but the frabric adapt unbrella design and leave the ships stuck on shield for earth use.

Starhopper first flight as early as this week; Starship/Superheavy updates

2019-03-18-174759-1170x829.jpg

Other views on website but it sure is ugly, shorter to scale of the eventual BFR versions and laning wing structure is oversized it would seem for the ship being built to test the engines.

D2Dk6F4X0AAQcSi?format=jpg&name=360x360

2019-03-18-181148.jpg

testing of heatshield tile video
tEX3bYcnXEzskZQF?format=jpg&name=small

Mr. Musk noted that the tiles passed their testing with flying colors, reaching white-hot orbital entry temperatures of roughly 1650 Kelvin (1,377 'C – or 2,510 'F).

Mr. Musk also revealed the hexagonal shape was chosen as it does not allow a straight path for hot gas to accelerate through any gaps in the heat shield – a critical component for reentry heating protection.

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#246 2019-03-19 17:50:01

louis
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From: UK
Registered: 2008-03-24
Posts: 4,633

Re: Starship is Go...

I think it was Everyday Astronaut who made the point that active cooling is actually a well established technology for rocket nozzles, basically pipes held together.  It doesn't seem to have been used on the bodies of rockets because, presumably, the main concern has been to keep the rocket's mass down.


Void wrote:

Well Louis, as I interpret what was presented, they will use the Hex tiles, and then study the erosion on them.  They seem to want zero erosion.  So, they will somehow, (Method not strongly defined), add active cooling where erosion occurs with the objective of eliminating erosion.

That article indicates that they want to be able to fly the Starship again the same day it lands.  So, the focus must be on Earth<>LEO & Earth<>Moon, as a couple of extra days downtime in a Mars trip can't be nearly as significant.


The vast majority of launches have to be not directly for Mars.  Satellites, Moon activities, Space Station stuff?, Refueling for the Moon and Mars, and then finally on occasion a trip to Mars.  Dr. Zurbin has mentioned that tying up a Starship for Mars is expensive, as it could have been used to launch a bunch of stuff to LEO and beyond during a Mars trip/habitat use.

I think that rather quickly using Starship to go to Mars will be replaced with dedicated advanced propulsion interplanetary craft, Ion, Fusion, Fission (Russia?), and ???? Something else?

My impression is that the tiles are not like space shuttle tiles.  And of course we think they are far less likely to incur impact damage to the tiles.  So, frankly, I would not be surprised if a early ship to Mars did not even have active cooling at all.  I have to imagine that they will first experiment with it on non-crewed ships.  To me that makes sense.

And that is the best I can do, from what I think I know at this time.  A fair amount of guessing as well.

GW was quite right it seems, but then active cooling in a more limited way is on the horizon, it would seem.

And the Moon is getting bigger and bigger.  Also, meshing with NASA plans for the Moon seems to be getting bigger and bigger.


Done.


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#247 2019-03-19 20:49:48

Void
Member
Registered: 2011-12-29
Posts: 3,011

Re: Starship is Go...

Louis,

I think that the method they will use for active cooling will be to prevent erosion of the tiles.  If the active cooling fails, then apparently the tiles can handle it, but they will erode.  And I am not very sure how they are going to combine active cooling with the tile method.  Will they actually squirt Methane or water through the tiles themselves?  I guess I will have to not make a greater fool of myself, and just wait for them to show what they intend to do.  Perhaps the area active cooled will not have those tiles?  Yes, I don't know.

Done.


I like people who criticize angels dancing on a pinhead.  I also like it when angels dance on my pinhead.

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#248 2019-03-19 20:57:17

Void
Member
Registered: 2011-12-29
Posts: 3,011

Re: Starship is Go...

More or repeated info:

https://www.businessinsider.com/elon-mu … rida-too-5

Quote:

On Sunday, Musk shared a video (above) of heat-shield tiles passing a "full duration" test.
These tiles are the most recent iteration of the technology SpaceX is developing to cool and protect Starship as it re-enters Earth's atmosphere and attempts to land. Such protection is necessary because spacecraft plow through Earth's atmosphere at roughly 25 times the speed of sound when they return, creating scorching-hot plasma that can vaporize steel.
Previously, Musk had said that Starship's heat shield would "bleed" rocket fuel from tiny pores in the spaceship's skin, thereby cooling it down. But a full "bleeding" system would have faced a number of unprecedented challenges, since clogged pores could lead to the destruction of Starship.
Musk's new video suggests that SpaceX has decided to go with a combination of hexagonal tiles and sections of Starship that'd transpire fuel.
"Hexagonal tiles on most of windward side, no shield needed on leeward [back] side, transpiration cooling on hotspots," Musk said, later adding: "Transpiration cooling will be added wherever we see erosion of the shield. Starship needs to be ready to fly again immediately after landing. Zero refurbishment."
In effect, Musk was hinting at SpaceX's iterative test plan for Starship: Build one with a tile-based heat shield, get it into orbit, land it, then examine the tiles for wear. In the spots where tiles look especially battered by 2,000-degree-Fahrenheit plasma heating, engineers will try to implement the "bleeding" cooling system.

I also read an article(s) that indicates that Starships will be built in Texas and Florida, the engines in California.  And they say that building the rockets outside of a building is a new feature, possibly a cost saving feature.  They did express some concern as to SpaceX's ability to get away with it.

I think this is a repeat of some materials that Louis previously presented, and it is even a bit outdated already, but here it is again then:
https://everydayastronaut.com/stainless-steel-starship/

Done

Last edited by Void (2019-03-19 21:23:34)


I like people who criticize angels dancing on a pinhead.  I also like it when angels dance on my pinhead.

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#249 2019-03-20 12:45:23

Void
Member
Registered: 2011-12-29
Posts: 3,011

Re: Starship is Go...

I find this of interest per a potential for Starship:
https://www.foxnews.com/science/trump-b … rom-brazil
Quote:

d States to use Brazil’s Alcantara Aerospace Launch Base for its satellites. (AP Photo/Evan Vucci)
During their first sit-down, President Trump and Brazil’s new far-right leader, President Jair Bolsonaro, arranged to sign several bilateral agreements, including one that lets the United States use Brazil’s Alcantara Aerospace Launch Base for satellites.
According to CBS, Trump said the U.S. will finalize an agreement with Brazil to be able to launch into space from the South American country’s north coast.

The Air Force told Reuters that launches from Brazil burn 30 percent less fuel, and rockets can carry larger payloads, because of the country’s location close to the equator.

Well that interests me.  It is not specified that SpaceX can launch propellant tankers from such a place, but 30% less fuel sounds very good for such a bulk item.

I am not interested in the politics, just the improved options for space flight.

Done.


I like people who criticize angels dancing on a pinhead.  I also like it when angels dance on my pinhead.

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#250 2019-03-20 18:30:01

louis
Member
From: UK
Registered: 2008-03-24
Posts: 4,633

Re: Starship is Go...

I think Space X's first launch was from an equitorial Pacific Island Kwajalein Island (part of the Marshall Islands).


Void wrote:

I find this of interest per a potential for Starship:
https://www.foxnews.com/science/trump-b … rom-brazil
Quote:

d States to use Brazil’s Alcantara Aerospace Launch Base for its satellites. (AP Photo/Evan Vucci)
During their first sit-down, President Trump and Brazil’s new far-right leader, President Jair Bolsonaro, arranged to sign several bilateral agreements, including one that lets the United States use Brazil’s Alcantara Aerospace Launch Base for satellites.
According to CBS, Trump said the U.S. will finalize an agreement with Brazil to be able to launch into space from the South American country’s north coast.

The Air Force told Reuters that launches from Brazil burn 30 percent less fuel, and rockets can carry larger payloads, because of the country’s location close to the equator.

Well that interests me.  It is not specified that SpaceX can launch propellant tankers from such a place, but 30% less fuel sounds very good for such a bulk item.

I am not interested in the politics, just the improved options for space flight.

Done.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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