New Mars Forums

Official discussion forum of The Mars Society and MarsNews.com

You are not logged in.

Announcement

Announcement: We've recently made changes to our user database and have removed inactive and spam users. If you can not login, please re-register.

#251 2019-01-22 15:36:55

Void
Member
Registered: 2011-12-29
Posts: 2,954

Re: Alternate BFR (Big Falcon Rocket)

I think I had a discussion of the real starship with SpaceNut recently. 

The clash was over active cooling.  I was the more ignorant one on that topic.  I had previous seen videos suggesting that the X15 had sinked heat internally.  So, I thought that that would be possible for starship.

SpaceNut told me that in fact a liquid would be squirted out of the ship through pinholes.  He suggested water, I had read Methane.

It turns out I have read word from the EM himself, and it seems that water or a fuel could be used.  So, I guess SpaceNut wins this one on balance.

Although it seem a fuel is slightly better, per this discussion.
https://twitter.com/PopMech/status/1087708141226283009
Quote:

EM
Replying to @PopMech
When going to ~1750 Kelvin, specific heat is more important than latent heat of vaporization, which is why cryogenic fuel is a slightly better choice than water

And no, I do not yet comprehend what he is saying.

So I will eat most of the crow, but you can have the aft sections SpaceNut smile

Last edited by Void (2019-01-22 15:37:44)


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

Offline

#252 2019-01-22 17:30:11

Void
Member
Registered: 2011-12-29
Posts: 2,954

Re: Alternate BFR (Big Falcon Rocket)

Not actually intending to crow, or be a jerk.  Just the facts please....

https://twitter.com/elonmusk/status/1087799667692392448
Quote:

Yes. Also, despite high outside heat, rapid water vaporization can counter-intuitively cause it to snap freeze & block cooling channels.

Just an honest fyi.  No arrogance felt or intended.

Done.


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

Offline

#253 2019-01-22 19:30:59

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 15,058

Re: Alternate BFR (Big Falcon Rocket)

Note for transpiring shield is its vents the material that is heated and a cold plate is a heavy skin which the fluid circulates.

The danger of methane which is flamable in oxygen is to great as a breech of the shield in entry with heat means it can burn on entry, and an internal breech of pipes used to circulate inside as well would lead to an explosion if its got oxygen once more.

So a safe alternative is to use the water which is not needed on a return home as you are going to reload the craft any ways.

Offline

#254 2019-01-22 22:39:35

kbd512
Moderator
Registered: 2015-01-02
Posts: 2,717

Re: Alternate BFR (Big Falcon Rocket)

Void,

The people at DLR working on transpiration cooling were well aware of the phenomenon that Elon Musk described and thus their system was adequately pressurized to preclude freezing.  I believe that their system was actually tested in a space flight demonstration as well.  It was only intended to cool the leading edges of the vehicle, not the entire vehicle.  The rest was handled with passive heat shielding materials.

SpaceNut,

As thin as the atmosphere is at the reentry interface, I'm not sure that CH4 is within the LFL.  However, I'd agree that water would be a better coolant due to the extreme heat of vaporization required.  Upon reentry, excess water is just additional dead mass that the vehicle has to bring to a halt.

I doubt that anyone at SpaceX has any practical experience with transpiration cooling unless they worked at NASA or ESA.  In point of fact, there's very little practical experience at any space agencies.  Maybe he purloined some bubbas from DLR.  That said, if he can make the transpiration cooling system work with Methane, then more power to him.

Offline

#255 2019-01-23 03:07:18

elderflower
Member
Registered: 2016-06-19
Posts: 1,087

Re: Alternate BFR (Big Falcon Rocket)

Whatever is transpired will dissociate in the plasma surrounding the vehicle, changing its heat transfer properties. I have no idea what would be the better selection. Water is favoured on the grounds of its high specific heat and high latent heat of evaporation for most cooling duties, but factoring in dissociation might make a difference.

Offline

#256 2019-01-23 11:22:06

Void
Member
Registered: 2011-12-29
Posts: 2,954

Re: Alternate BFR (Big Falcon Rocket)

This is all fine.  As a associate once told me, "Sometimes you catch the bus, and sometimes the bus catches you".

Done.


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

Offline

#257 2019-01-23 11:58:35

kbd512
Moderator
Registered: 2015-01-02
Posts: 2,717

Re: Alternate BFR (Big Falcon Rocket)

Elderflower,

If it didn't actually work, then they wouldn't use it and the fact that it didn't work would've been discovered during initial ground testing.  The enthalpy or heat of vaporization is what matters and it's about 4.7 times higher for H2O than CH4.  Dependent upon the quantity required, there may be some storage advantage for CH4 over H2O and, of course, BFS has to carry substantial quantities of CH4 anyway.  However, a substantial quantity of water is also required for crew radiation shielding and consumption during long duration missions.  If SpaceX has determined that CH4 works better for their application, then great, use CH4.

I keep looking at this and wonder if the right way to do this is some combination of stainless with transpiration for the propellant tanks along with carbon and/or boron composites for radiation and debris protection with an advanced ceramic heat shielding for the pressurized portion of the ship.  When combined with the double side wall propellant tanks I proposed, it would reduce the mass of the crewed portion of the ship, provide the required structural rigidity for the propellant tanks, simplify fabrication (no need to build and support the landing propellant tanks within the primary tanks and the structural reinforcement mass is transferred to the side wall, where it's needed most; it could be fabricated on a welding mandrel, just like SLS), and use propellant to take care of cooling the propellant tanks during reentry and re-pressurizing the propellant tanks for the reentry and landing burns.

Offline

#258 2019-01-23 12:31:44

Void
Member
Registered: 2011-12-29
Posts: 2,954

Re: Alternate BFR (Big Falcon Rocket)

Interesting sometimes water is mentioned and sometimes liquid fuel.  I guess they might still be in a contest.  May the best fluid win.
https://twitter.com/elonmusk/status/1088087441037131777
Quote:

Elon Musk
Replying to @Teslarati
310S stainless is better for high temp outer skin, as it can take ~1450 Kelvin, so active cooling with cryogenic fuel only has to mitigate 300 degrees of delta temp

I am searching to learn.

So the two windward layers might be different types of stainless steel from each other.

Done.

Last edited by Void (2019-01-23 12:36:59)


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

Offline

#259 2019-01-23 13:32:43

Void
Member
Registered: 2011-12-29
Posts: 2,954

Re: Alternate BFR (Big Falcon Rocket)

Curiosity also makes me wonder what is the difference in rigor between;
-Aeroburn from LEO
-Aeroburn to Mars
-Aeroburn to Earth from Mars.

Done.


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

Offline

#260 2019-01-23 15:32:11

kbd512
Moderator
Registered: 2015-01-02
Posts: 2,717

Re: Alternate BFR (Big Falcon Rocket)

Void,

NASA has papers with dV increments for the expected TMI, MOI or aerobrake / aerocapture, TEI, and EOI or aerobrake / aerocapture burns from now into the 2030's.  SpaceNut, GW, and I have posted the papers at one point in time or another.  Just Google "mars tmi dv increments".  There's plenty of free data and software to play with.  NASA has GMAT, MALTO, JAT, and other software that's open source.  The high fidelity trajectory / mission planning software is restricted due to ITAR.

Edit: The high fidelity software is called Copernicus.  You have to have a contract with NASA or the federal government that requires trajectory analysis to gain access to it.

Edit #2: If you're a bonafide federal contractor performing mission trajectory analysis work for NASA or the federal government, here's the link to obtain Copernicus:

Copernicus Trajectory Design and Optimization System (Version 4.x)

I believe the latest update came about in May of last year, but there's a page on NASA's website to obtain news about software updates.

Last edited by kbd512 (2019-01-23 16:12:51)

Offline

#261 2019-01-23 18:56:36

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 15,058

Re: Alternate BFR (Big Falcon Rocket)

Void wrote:

Curiosity also makes me wonder what is the difference in rigor between;
-Aeroburn from LEO
-Aeroburn to Mars
-Aeroburn to Earth from Mars.

Done.

LEO burn has the highest starting mass plus payload as you need to accelerate to get out of orbit and on the way to mars.

Burn to direct enter mars atmosphere is less as the fuel and items jetisoned along the way makes the craft mass less.

The launch from Mars direct to earth versus from a docked on orbit return vehicle are different equations.

Offline

#262 2019-01-24 22:54:02

Void
Member
Registered: 2011-12-29
Posts: 2,954

Re: Alternate BFR (Big Falcon Rocket)

Quote:

LEO burn has the highest starting mass plus payload as you need to accelerate to get out of orbit and on the way to mars.

That is good information, but not quite what I was after.

I am thinking that a fully loaded craft aerobraking to Mars will as you say have reduced it's propellants to a minimum.  Good observation.  I did not think of that.  But of course it will be loaded to the gills with cargo.  But it will come in at interplanetary speeds, and yet perhaps be near it's less sunward part of an elliptical orbit (Lower speed)?  I guess the Hohmann Transfer burn confuses that a bit.

A returning craft from Mars to Earth may not have much cargo or propellants.  But it will come in at interplanetary speeds, and yet perhaps be near it's more sunward part of an elliptical orbit (Higher speed)?  I guess the Hohmann Transfer burn confuses that a bit.


And a craft returning from LEO to the Earth's surface would have a minimum of propellant, and a variable but probably smaller cargo.
And it would be coming in from a relatively circular orbit.

Return from the Moon I have not mentioned.  Somewhere between in stress?

You can answer or no.  I know that the way I present this is annoying to many of you as you are precision math nuts.  Sorry it's how I am.

Done.

Last edited by Void (2019-01-24 22:55:33)


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

Offline

#263 2019-01-25 18:37:15

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 15,058

Re: Alternate BFR (Big Falcon Rocket)

The rocket aerobraking into Mars orbit is what we would be doing if we have no extra fuel. https://en.wikipedia.org/wiki/Aerobraking

We make multiple passes into the lower thick part of the atmospher with the help of heat shielding.

300px-Animation_of_Mars_Reconnaissance_Orbiter_trajectory_around_Mars.gif

https://www.space.com/2439-tricky-task- … -mars.html

https://www.reddit.com/r/spacex/comment … e_on_mars/

The real question comes back to the hardware design and needs as to using the heat shield once and land on the way in rather than wasting the time making multiple passes for what ever the period of time is needed. If we are not leaving anything in orbit we might as well go in direct.

Offline

#264 2019-02-04 19:06:44

Void
Member
Registered: 2011-12-29
Posts: 2,954

Re: Alternate BFR (Big Falcon Rocket)

OK, more "Hear Say">>>>And then speculation of a risky type.

https://www.universetoday.com/141408/el … -possible/
Quote:

Elon Musk’s New Plan is to Get to the Moon as Fast as Possible

For Elon Musk and SpaceX, the company he founded to reignite space exploration, a great deal hinges on the creation of the Starship. This super-heavy launch vehicle, which was has evolved considerably in the past few years, will eventually replace the Falcon 9 and Falcon Heavy as the mainstay of the SpaceX fleet. Once operational, it will also facilitate missions to the Moon and eventually Mars.
Once again, Elon Musk has used his social media platform of choice to share the latest details about the Starship‘s progress. As he shared in a series of tweets, which began on Thursday, Jan. 31st, the company has commenced test-firing the Raptor engine at their Rocket Development and Test Facility in McGregor, Texas, and is pushing towards the Starship’s first mission.
The Raptor is a staged-combustion reusable rocket engine powered by cryogenic liquid methane and liquid oxygen (LOX), rather than the kerosene and LOX combination (RP1) which powers the Merlin rockets used by the Falcon rocket family. Once complete, the Starship will have seven Raptor engines, each of which will provide twice as much thrust as the Merlin 1D used by the Falcon 9.


News of the engine’s test-firing began with Musk posting two pictures of the Raptor engine along with the caption, “Preparing to fire the Starship Raptor engine.” In addition to the pictures, Musk took the opportunity to share specifications that provided some clues as to what path the company is planning to take with the Starship in the near future.
For example, Musk indicated that the current version of the engine is simplified compared to later versions, and is tailor-made for speed:
“Initially making one 200 metric ton thrust engine common across ship & booster to reach the moon as fast as possible. Next versions will split to vacuum-optimized (380+ sec Isp) & sea-level thrust optimized (~250 ton).”

Here, Musk is alluding to the first crewed mission of the Starship, which is scheduled to take place in 2023. According to the plan that Musk announced back in September, this inaugural flight will see Japanese fashion designer and art curator Yusaku Maezawa and a group of artists being taken on a flight around the Moon.

This mission, the #dearmoon project, will be the first private lunar passenger flight in history and is intended to help fund the development of the Starship. The flight will last a full week and will involve the passengers using the journey to inspire their particular brand of artwork. By streamlining the development of the engine, Musk is indicating that he may be accelerating the timeline.
This update was followed on February 2nd with Musk tweeting a photo of himself standing by the engine and announcing that it had made it to the McGregor facility. On the following day, Musk posted two more tweets (shown above) of the Raptor engine being test-fired. The two video segments show the engine igniting and achieving about three seconds of clean thrust before being shut off.

As you can see from the videos, the test was a dazzling display of both light and sound. Aside from the beautiful, multi-colored stream of fire that the engine produces, there is also the ear-shattering noise it makes (which sounds like a cannon firing repeatedly). Elon followed the video clips with a still shot of the engine firing with the caption, “First firing of Starship Raptor flight engine! So proud of great work by @SpaceX team!”
Other recent changes that were shared by Musk in recent weeks include the fact that the first stage of the launch system (the Super Heavy) could initially fly with less than 31 Raptor engines (as was originally proposed). The reasoning behind this, according to Musk, is for the company to cut their losses “in case it blows up“.

Artist’s impression of SpaceX’s Starship deploying cargo to Low Earth Orbit (LEO). Credit: SpaceX
In addition to that, Musk also indicated that the Starship‘s Reaction Control System (RCS) thrusters will have a simplified design. When asked if he was still planning on using methalox fuel to power them, he tweeted: “Cold gas thrusters only. Will use body flaps & main engines for landing orientation, so won’t need high thrust reaction control. Simplifies things considerably.”

All of this suggests that Musk is looking to cut costs and push ahead on production. It also raises the question of whether or not this has anything to do with the recent announcement that SpaceX will be laying off almost ten percent of its employees, while Tesla will similarly be laying off seven percent of its workforce.
Musk attributed the latter to the steady growth of the company’s workforce, which has led to the unwanted duplication of some positions. In the case of SpaceX, however, Musk claimed that the layoffs were caused by the company’s “absolutely insane” projects, specifically Starlink (the SpaceX initiative for providing high-speed global internet access via satellite) and the Starship.
As such, it makes sense that some trimming and expediting is seen as necessary as far as the development of the Starship is concerned. These latest updates also come shortly after Musk revealed that the ship’s hull design had changed. This was apparent when the miniature version – the “Starship Alpha” – was photographed being assembled over the holidays.


Artist’s impression of what the completed Starship Alpha will look like. Credit: SpaceX
Thanks to multiple shutterbugs who kept an eye on the South Texas Launch Site, it became apparent that the Starship – like it’s prototype – would be constructed out of stainless steel rather than carbon composites (as had originally been proposed). Musk confirmed this shortly thereafter, and reiterated it once again on Jan. 31st, tweeting:
“To be clear, I’m confident that a stainless steel ship will be lighter than advanced aluminum or carbon fiber, because of strength to weight vs temperature & reduced need for heat shielding.”
As always, Musk is keeping the public engaged on the progress of his “insane projects”. And while there might be some bumps along the way, Musk is nothing if not tenaciously-driven. He’s also no stranger to financial hiccups and setbacks, but has always managed to deliver in the end. And where the Starship is concerned, he’s hardly alone in wanting to see it succeed.

So, from the above, I think that the intention is to facilitate Starlink, prove the BFR(Super Heavy/Starship) as much as is possible, get satellite launch jobs, and to try to get paid for activities involving the Moon. 

The Moon is a great way to prove the ship.  Kind of following the steps of the 60's and 70's space programs which ultimately landed humans on the Moon.

If they can survive financially and prove things like that then it may be that if they continue to Mars, certain elements of the USA National/West/Global Community will opt in with money, for consideration of sub projects to be included.  It would be silly for Starship to go to Mars without a science interest.  To get science done however, participants would have to pony up funding. $$$

……

Now for the things that may annoy you even more:

At the top of this post, please find an article linked.  Please find the picture of a possible Starship with the caption "Artist’s impression of SpaceX’s Starship deploying cargo to Low Earth Orbit (LEO). Credit: SpaceX" under it.

I have previously suggested that a version of Starship, could be made on the cheap, without heat shield, and having the ability to maybe go SSTO, or in fact also use the Super Heavy if desired.  This ship would not come back to a planet where significant atmosphere exists.  That then would indicate it be part of a space station or a Moon base.

In general other than that SSTO is out as a practical matter.  But what if you could go SSTSO  (Single Stage to Sub Orbital)?  If you had the nose door in the depiction, could you release a self propelled payload?  A payload that would finish itself to orbit.  The advantages might be that you can get more payload up above the Troposphere, and that you don't need active cooling or ablative cooling on the ship, as you don't move that fast before you come back down to the denser atmosphere.  That is my assumption, and we know what assumptions can do.  So I don't state it as provable fact, rather as a question which I hope will be answered some day.

Once the method might be demonstrated, then eventually could humans and experiments do sub orbital in a manner similar to New Shepard, but not capsule & parachutes?  (There is a nose door).

And I wonder if such a flight could go from Texas to Florida or vice versa, generally flying over water so that a water abort is an option.  In other words a tourist trap including a useful distance of travel.

Why do it?  I just consider that not using the Super Heavy reduces some kinds of risk and may reduce the ticket prices.


There. Done like a burnt weenie sandwich~!

Last edited by Void (2019-02-04 19:26:36)


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

Offline

#265 2019-02-05 04:18:15

elderflower
Member
Registered: 2016-06-19
Posts: 1,087

Re: Alternate BFR (Big Falcon Rocket)

Super heavy booster is designed for recovery and reuse, The marginal cost of another flight is thereby minimised (fuel, transport and refurbishment ready for the next flight), the hardware having been already paid for.

Offline

#266 2019-02-05 11:03:40

Void
Member
Registered: 2011-12-29
Posts: 2,954

Re: Alternate BFR (Big Falcon Rocket)

Elderflower said:
Quote:

Super heavy booster is designed for recovery and reuse, The marginal cost of another flight is thereby minimised (fuel, transport and refurbishment ready for the next flight), the hardware having been already paid for.

Yes, but even if a Super Heavy launch only costs 1/20th that of SLS, it is still an expense.  Also the combination of total engines is 31 + 7, if a full set of engines are used according to recent specs for the devices.  Each engine is a chance for something to go wrong.  I understand that many engine problems may be worked around in flight without a cascade failure.  However if you launch both devices together in a stack, there are chances that one blowing up will take out the other as well.

I was just shaking the package to see what other things it might be able to do.

For instance if you are going to certify BFR(Super Heavy/Starship) for Tourists and for passenger delivery, it would make sense to first certify the Starship.  Then you might do space tourism with it, probably sub-orbital.  And then I wonder weather the Starship could do continental travel hops?  That could be of value in itself, and also to test and rate the system.

As for the Super Heavy, at first you would only involve it for payload delivery to orbit, BFR(Super Heavy/Starship) stack, and also for professional crew use.

The question of using Starship as a 1st stage with a powered 2nd stage in its front trunk, is open to a requirement for more information.

It may be a no no.  It may be that open the hatch at altitudes attainable would blow it apart.  This is in the set of questions that would go with this thinking. 


But if it were worth the trouble to do some of these things, there could be the possibility that the stainless steel by itself would be enough for the starship.  No active cooling, no ablative coatings.

But there again I come up far short of a full deck on doing such an analysis.

I understand precision, I also understand innovation.  Usually when you try to do something new with something old, it does not work out.

That does not mean you should not have a look at it.

No fools were harmed in this conversation.

Done.

Last edited by Void (2019-02-05 11:05:28)


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

Offline

#267 2019-02-18 09:23:16

Void
Member
Registered: 2011-12-29
Posts: 2,954

Re: Alternate BFR (Big Falcon Rocket)

Well this is said to be materials from Elon Musk, so it could have gone on other topics, but I don't want to step on other current conversations. 

So, I will put it here.
https://www.teslarati.com/spacex-ceo-el … -falcon-9/
Quote:

SpaceX
SpaceX CEO Elon Musk says that BFR could cost less to build than Falcon 9

……

But what I am really interested in in the article is this:
Quote:

Randomness as a human
@epoxy101
· Feb 10, 2019

Replying to @elonmusk and 3 others
will it be cheaper than F9 for kg to LEO for instance?

Elon Musk

@elonmusk

At least 10X cheaper

972
9:16 PM - Feb 10, 2019

While many can focus only on Mars, I think I see here that the new reusable launch system, if it measures up somewhat the above projection, will change all sorts of things.

For one thing, if it comes close, I would anticipate that getting resources from the Moon as a contribution to space projects could really take off.  So the launch system itself is not the only factor, but other hidden factors should emerge.  Space will be ~10x more doable in general?

So costs go down, and more projects should emerge, which would then justify building more ships.

I wonder about orbital solar power.

Done

Last edited by Void (2019-02-18 09:32:32)


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

Offline

#268 2019-02-18 10:56:26

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 15,058

Re: Alternate BFR (Big Falcon Rocket)

Well if he is not starting a new plant location building he has already done the investment for making the rocket as he is reusing the existing equipment. Have not seen how many BFR he will build as of yet but much like Falcon 9 and Falcon 9 heavy the numbers for cost reduction is based on how many are in the system capable of launching.
Orbital solar has it own problems depending on where the power is to go for use.

Offline

#269 2019-02-18 13:22:39

Void
Member
Registered: 2011-12-29
Posts: 2,954

Re: Alternate BFR (Big Falcon Rocket)

Quote the SpaceNut even more:

Well if he is not starting a new plant location building he has already done the investment for making the rocket as he is reusing the existing equipment. Have not seen how many BFR he will build as of yet but much like Falcon 9 and Falcon 9 heavy the numbers for cost reduction is based on how many are in the system capable of launching.
Orbital solar has it own problems depending on where the power is to go for use.

Fair sayings.  Still if SpaceX can lower the cost of a kg to orbit by an order of magnitude better than it's own Falcon 9, that is saying something.  But I know in my hart, that the USA gov. will not allow a monopoly, no matter how fantastic SpaceX gets.  So they will nurse others such as Blue Origins into the sky as well.  That coupled with the Moon and perhaps even asteroids, suggests that indeed while orbital solar power's chances are enhanced, so even more becomes possible for synthetic gravity machines in orbital locations.

That would indicate then to put some of the useful eaters and useless eaters (Me?) into orbit, and so the then market for that orbital solar power would be in orbit.  This would take some load off of the Earths ecosystem, and really improve the prospects for the human race. 

But there may be Earth products.  I won't go into that yet.

Done.

Last edited by Void (2019-03-04 13:17:04)


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

Offline

#270 2019-03-04 13:18:21

Void
Member
Registered: 2011-12-29
Posts: 2,954

Re: Alternate BFR (Big Falcon Rocket)

This looks like some very interesting materials I am reading.

Keep in mind that I am just that, a reader, not an expert.

https://www.universetoday.com/140518/go … ropulsion/
Quote:

Best Chemical Rocket Speeds and Times
Refueling a large rocket like the SpaceX BFR can produce surprisingly good trip times to Mars.
Multiple orbital refuelings of the SpaceX BFR at a high orbit can maximize the speed of the BFR. A fully fueled SpaceX BFR would shorten the one-way trip to Mars to as little as 40 days. A parabolic orbit would be used instead of a Hohmann transfer.
Space Missions to Mars have been small spacecraft. The entire mission was launched from Earth. This means most of the fuel was used to get the system off of the Earth. The final stage is tiny and slow.

By refueling the SpaceX BFR in orbit, it is possible for a large chemically powered space mission with up to 10.0 kilometer per second delta-V. This is about 100 hundred times larger than prior Earth to Mars missions and three times faster.

There are several propulsion systems mentioned, that I think can be discussed, as they mostly look like their functions would be complementary to a "SuperHeavy/Starship" system.

And they do propose an Alternate BFR, where they claim that a "SuperHeavy/Starship" system, could go to Mars in 40 days, by having propellants topped off in high Earth Orbit, and skipping the Hohmann Transfer method and using a parabolic? Elliptical? transfer orbit.

Well, that sounds great to me.

I had suspected things like this suggestion for some time.  I think O.F. also mentioned a fuel depot being put in orbit of Mars.  That is one way to expand the capabilities of the system beyond the standard "Mars Direct / Hohmann Transfer method".

I approve of the SpaceX plan to use the task of launching Starship from LEO, and just getting it to the Martian surface.  That is a great measure of just how powerful at minimum you would want Starship to be.  But it is just plain silly not to then think about augmented mission methods.

For instance the philosophy of reusing hardware is a good mark to measure to, but I should not be a cage which prevents useful innovations.  It is fairly obvious, that you could link several Starships together, and use one or two as a 1st and 2nd stage.  Where the assembly would travel from LEO (Not the surface), to high Earth orbit.  In this method you should be able to reuse everything.  Two Starships would return to Earth, one would continue on to Mars, from high Earth orbit, and with it's propellants topped off from that location.

But if you can pre-position a Depot in orbit of Mars, then you could also take an external tank / Depot with you, space shuttle style.  Only you would not fly up to LEO like that.  You would get a fuel depot into LEO, and then attach it to Starship.  And yes for certain operations it could be expendable, or maybe it could be recovered in some situations.

In the article they do not indicate method of achieving orbit, in a manner I can understand.  In my little world a ballistic capture would be wonderful, as in some situations apparently an aeroburn would not be need.  However, ballistic capture methods actually take longer than methods using Hohmann transfer.  And so I have to suppose that the method will have it's own quirks.

https://www.nextbigfuture.com/2018/06/s … ation.html
Quote:

An orbital refueling of the SpaceX BFR at a high orbit to maximize the speed of the BFR to send one that is fully fueled would shorten the trip down to as little as 40 days.
Space Missions to Mars up to now have been small satellites where the entire mission was launched from Earth. The delta-V has been about 3.2 to 3.5 kilometers per second.
By refueling the SpaceX BFR in orbit and assembling a few stages in high orbit, a large chemically powered space mission can get up around 9.0 kilometer per second delta-V.


We will not need to wait decades for super-advanced space propulsion to be developed for less than 60-day trips to Mars. Elon Musk and SpaceX should have the BFR flying within 5 years.
Short 45-60 day or even 30-day trip using large multi-stage chemical rockets launched from high orbits after refueling will make large fast missions easy. The shorter times mean far less radiation and health issues for astronauts and passengers. The far larger ships means water and other material for radiation shielding.
Bigger and more powerful spaceship will be like cruise ship versus dingy

The Mars missions we have sent have been less than 1000 kilograms but putting a few BFR payloads together could send 1000-ton Mars missions.
SpaceX is bringing the next BIG future in space.
In World War 2, after D-Day there was 8,500 tons per day of cargo being sent to the beaches. Fifty SpaceX BFR would be able to regularly shuttle that amount of material to orbit. We will be able to invade space (moon, orbits, lagrange points, Mars) the way Europe was invaded by the allies.
Power starved up to now
The low power and delta-V budgets have forced space mission planners to use slower hohmann transfers. Those are the most economical but are long circular orbits that look more like orbits around the sun than targeting a flight to Mars.
Elliptical and parabolic orbits have less curve and are much shorter and much faster trips.
NASA has calculated faster trips where a mission is assembled or refueled in high orbits.

The SpaceX subreddit had analysis of the payloads and times to Mars using refueling.

Earth-Moon Lagrange 2 or EML2 is one of 5 locations where earth’s gravity, moon’s gravity and centrifugal forces all cancel out. It lies beyond the far side of the moon at about 7/6 of a lunar distance from earth.
EML2 would make a great transportation hub. Not only for travel to destinations throughout the solar system but also within our own earth moon neighborhood.

The SpaceX BFR will be fully reusable and able to carry 150 tons for Earth to Low Earth Orbit but it could refly once to seven times per week. So a lot of refueling missions and taking large pieces of space stations and moving large payloads between low earth orbit, high orbits, moon and lagrange points will be easy.
Place Multiple Bigelow Hercules resupply depots at each Lagrange point, various Earth orbits, lunar orbit and Mars Orbits

Nextbigfuture has described how very large rotating space stations around the earths equator could be made to provide radiation safe living with full one gravity equivalent from rotation.
This would be safe be part of a safer path to space development.
* Build many SpaceX BFRs
* Build massive orbiting space stations around the equator that provide radiation safety and one full gravity equivalent. With a few SpaceX BFRs able to launch many times per week, 150 tons per launch, a massive space station of tens of thousands of tons could be built in 1-2 years. A key would be a fast assembling system for connecting large 50-100 ton earth built modules in space
* Make larger lunar bases Joseph Friedlander described part of using the BFR to make lunar bases here at Nextbigfuture
Robert Zubrin has described better plans for lunar and Mars colonization.
* SpaceX BFR could assemble Mars transportation where multiple SpaceX BFS are connected and set up to rotate to provide the equivalent of gravity during a mission to Mars. The larger loads and reusability of the BFR could be used to assemble larger systems for providing some radiation protection.
* Going to the surface of Mars would require that colonist to live with lower gravity. Rotating one G equivalent stations could be placed in orbit around Mars and the Moon so that colonists of the Mars and Moon could go to one-G locations every so often to counter the lower gravity of the Moon and Mars.

Mars ISRU is being developed
SpaceX is already developing high-efficiency CO2 capture with H2O to form liquid CH4 (methane) & O2.
After landing on Mars, Sabatier reactors would be used to gradually refuel each Big Fucking Spaceship. The Sabatier process follows the laws of thermodynamics and thus requires a power source to heat the inputs, as well as cool the outputted methane and oxygen into fuel-grade cryo-cooled liquids. NASA is working on KiloPower and Megapower nuclear reactors. SpaceX could also bring large amounts of solar panels. Solar would half as energy dense on Mars but we could bring a lot more panels in a BFR.
Written by Brian Wang, Nextbigfuture.com

That's enough for now.

Done

Last edited by Void (2019-03-04 13:48:31)


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

Offline

#271 2019-03-04 17:12:11

kbd512
Moderator
Registered: 2015-01-02
Posts: 2,717

Re: Alternate BFR (Big Falcon Rocket)

Void,

Starship really needs an electric in-space / cruise propulsion system of some kind.  It could be any of a variety of technologies, but the salient point is that short bursts of power from chemical rockets followed by screaming interplanetary reentries is not the correct way to do reliable and versatile interplanetary transportation.  It's always best to establish stable orbits and then reenter.  We've done it the other way in the past because we lacked the technology to do it better.  We don't suffer from that problem now, so it's time to consider better methods that are less likely to result in catastrophic damage to the vehicle.  "Missed it by just that much" is not something you want to hear as a paying passenger.  Paying customers want powered and controlled flight provided by experienced veteran pilots at all times.

People look at the orbital stations as unnecessary diversions from landing on something.  I look at the orbital stations as a network of space ports that provide repair / refueling / logistics services for a fleet of space transports.

Offline

#272 2019-03-04 17:29:08

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 15,058

Offline

#273 2019-03-04 18:12:21

Void
Member
Registered: 2011-12-29
Posts: 2,954

Re: Alternate BFR (Big Falcon Rocket)

I really think that synthetic land is the way to go.  Starting with smaller synthetic gravity machines.

In my opinion, the Orbit Space of Mars, or Orbitsphere, and the objects in it both natural and synthetic will be at least as valuable as Mars itself.  And it may turn out that Mars is just a place adults drop down to, in order to do a task, or be amused.  If you really think about it wouldn't we prefer to have a terraform improved Mars that we might visit as desired/required.  And yet to have a very safe Earth like place to live in in orbit.

Where sci-fi typically deals with the Moon, Mars, and Stars, I am coming to the conclusion that we live in a different place than that model.

I think we want to hope to build Mars into a Mini-Pseudo-Earth, that's fine you can make a biosphere perhaps.  But some mining as well.

As I see it there could be a progression which reaches all the way out to the presumed Rogue Planets between the stars.  Stars eventually?  Maybe.  But, if there are 100 to 100,000 Rogue planets for every star, then there is plenty of material to work with more local.

So, as you get out to the moons of Saturn, Uranus, Neptune, perhaps you take them apart.  At first lots of ice.  Due to that it will important to move metallic/stony materials to these places.  In fact I think solar sailing robots could simply impact the ice, periodically, and then mining resume.  The metals/stones used for synthetic gravity machines.  The ices made into giant water drop shell worlds.  Synthetic land inside around the center, perhaps a protective shell around a surface ice layer.  And once enough ice is removed, then the core of the moon becomes a metals and stone source.

In my view, solar can work well from Mercury to Jupiter.  To go to Saturn and beyond all the way to the Rogue planets (I hope), then some fusion power is needed.

Once this were all done, then it might be time to travel to other star systems, far in the future.

https://www.universetoday.com/140518/go … ropulsion/
Quote:

Advanced Propulsion : Positron Dynamics – Positron Catalyzed Fusion Drive
Positron Dynamics has given updates to NIAC and Brian Wang has interviewed Positron Dynamics CEO Ryan Weed.
The problems to create and store antimatter are avoided. Krypton isotopes are used to generate hot positrons. More isotope can made using neutron producing reactors. This avoids the problem of creating antimatter.
Antimatter is not stored, which is great because we do not know how to store antimatter. Positrons are created and then directed into a process which produces fusion propulsion. This also solves the problem of using antimatter to generate propulsion.

I am not sure how real the above is, but if it becomes possible, I don't see how far off a fusion power plant based in that process would be.  So, I am thinking that the path forward is from the inner solar system to the outer solar system, through the Oort Cloud, to Rogue Planets.

And if you have Fusion, the Saturn, Uranus, and Neptune are huge tanks of fuel.


And I agree with you kbd512, and Spacenut, on the need for better propulsion methods.  It is insane to do the current version of BFR, LEO>Mars Surface,  but it is the best possibly available system at this time.
Done.

Last edited by Void (2019-03-04 18:54:04)


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

Offline

#274 2019-03-04 21:37:46

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 15,058

Re: Alternate BFR (Big Falcon Rocket)

Interplanetary transportation is more along these lines...
SpaceX's Crew Dragon Launch Could Make Space Hotels A Reality


https%3A%2F%2Fblogs-images.forbes.com%2Fjonathanocallaghan%2Ffiles%2F2019%2F03%2Fbigelow-main-1200x742.jpg

Offline

#275 2019-03-05 08:16:32

Void
Member
Registered: 2011-12-29
Posts: 2,954

Re: Alternate BFR (Big Falcon Rocket)

A very encouraging post SpaceNut.

I would say that there are seeds for a great future included in that.

Done.


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

Offline

Board footer

Powered by FluxBB