Tuesday, June 29, 2010

Your Handy Rocketpunk Manifesto Travel Planner

ISS 'below' Earth
New! Unique! Almost worth the free download! It's the one and only Rocketpunk Manifesto Travel Planner, available in all flavors of plain vanilla Excel. I did this workbook for my own amusement, inspired by this recent post, then decided to offer it to an indifferently awaiting world.

It is tailored for a high specific impulse drive, and trips across planetary distances conveniently measured in AU. If the ship pops through an FTL rabbit hole at the midpoint, that is between you and Albert Einstein. It has no effect on this worksheet, except that the given travel distance is misleading.

Each worksheet is laid out as three columns: mission characteristics, ship characteristics, and (inevitably) cost estimates. User entry values are across the top, in light blue.

The mission column models a steady acceleration, coasting phase, and steady deceleration, all in flat space. The ships I was modeling are fast enough, with transfer speeds in the dozens of km/s, that solar space beyond 1 AU is fairly flat for them. Real ships don't have constant acceleration, either - acceleration increases as propellant is burned off - but this gives a decent first approximation of travel time.

Providing a coasting phase is more efficient than a brachistochrone orbit, because you aren't putting on speed only to almost immediately take it off again. A coasting distance of zero corresponds to a brachistochrone. (If you change the distance, reduce the coasting phase first - Excel will freak out if you make the trip distance less than the coasting phase.)

Note that I round off 1 g to 10 m/s/s, versus ~9.8 m/s/s, just as I round off 1 AU to 150 million km. Acceleration is in milligees; drive specific impulse is in seconds (not exhaust velocity in km/s). The worksheet computes travel time, burn time (accelerating and decelerating), mission delta v, peak travel speed, and initial and final acceleration.

The second column is for basic ship characteristics. The first user entry is departure mass - the ship, fully loaded and fueled. The second is drive fraction - the percentage of the ship's arrival mass (what reaches the destination) that is given over to the drive engine, including shielding, radiators, etc.

The third user entry is keel fraction - the portion of all-up departure mass given over to the framework that holds drive engine, tankage, and payload together, along with bells & whistles such as the navigation and comms equipment. Since these are low acceleration deep space ships I used a modest 5 percent for this figure. (Each section of the ship would also have its own internal bracing.)

The final user entry here is tankage fraction, as a percentage of propellant load. l used a generous 10 percent, since for liquid hydrogen fuel the tankage must include a cryogenics plant.

There is no user entry for the payload. It is calculated (and shown on the right hand column, just below the user cost entries). The payload is simply whatever mass allowance remains once necessary mass has been assigned for the drive engine, keel, tankage, and of course propellant.

I also don't give a figure for the dry mass of the whole ship, because this depends on the payload. The payload figure given is gross payload - the whole payload section, including any hab compartment, cargo bays, the cargo itself, whatever. I do give a figure (also over on the right) for the mass of the bus, the ship structure minus the payload. So the dry mass is bus mass plus whatever part of the payload is 'fixed.'

Finally, the right side of the worksheet permits some cost estimates. The first is fuel energy cost (not propellant cost), measured in US cents per kilowatt hour. The figure I used, 2 cents per kW/h, is roughly the current cost of nuclear electric power, approximating the case of having to breed fusion fuel. This is the price to beat if you're mining He-3 from Out There somewhere.

The next user entry is hab mass per passenger berth, probably several tons. I used 5 tons per berth for trips of a few weeks, up to 25 tons per berth for an 18 month mission requiring long term life support.

The next entry is ship cost, per ton of dry mass, with a unit value of $1 million, which is about what a jumbo jet costs. If you want cheaper ships, just enter something less, like 0.3 for $300,000 per ton. The final figure, 'annually,' is what the ship costs you each year, for paying off the building loan plus operating costs, as a percentage of building cost. I use 20 percent.

All of this lets me calculate, i.e. guesstimate, the cost of a passenger ticket, helpfully broken down into berth charge ('rental' of the berth space, for duration of the trip), plus a carriage charge, the energy cost of actually making the trip.

A host of details are ignored, such as a reserve propellant margin, that you don't want to ignore in practice, along with other details such as necessary downtime between missions. And you know what resides in the details.


It is not exactly a 'ship design' tool - it doesn't even give the official mass and cost of a ship, but it is a way to suss out some ship characteristics required for long space trips with high specific impulse drives, whether Realistic [TM] midfuture drives or more advanced torchlike drives.

Naturally I took it for a test drive, with the results that you'll see. Drive engine characteristics (except for specific impulse) are calculated, not user input, but I fiddled each sim to represent a ship with a hefty 1000 ton main drive engine. For the first two sims this drive puts out 1 gigawatt of effective thrust power, the performance level of a nuke electric or solar electric drive that we could probably develop now if we put Pentagon money into it.

With this drive a ship with a mass of some 5500 tons should be able to reach Mars in three months, burning off about 2000 tons of propellant and delivering a 900 ton payload section. As a transport it could carry about 120 passengers, each paying about $1.2 million for the one way trip. Cargo rides cheaper, about $130,000 per ton.

The same drive plant, with a different specific impulse setting, will send a 1700 ton payload to Saturn in 18 months, one way - a passenger ticket costs $17.5 million, but a measly half million to ship a ton of cargo.

The next few sims step up drive performance to 10 gigawatts from a 1000 ton unit. With this drive a 3500 ton ship can just barely reach Mars in 21 days (at opposition), carrying a nominal 35 ton payload, enough for a handful of passengers. But a slightly slower trip, 30 days, allows a vastly more economical ship. For this mission our ship has a departure mass of 6400 tons and delivers a 1700 ton payload, carrying more than 300 passenger. A one way ticket to Mars now costs $440,000; a ton of cargo can be shipped for $80,000.

A longer and slower trip, three months, turns out to cost more for passengers, due to (assumed) greater life support requirements, but cargo cost falls to $40,000 per ton. Notice the enormous size of this ship: Departure mass of 35,000 tons, and a 16,000 ton payload section.

Then I tried the drive out for going from Earth orbit to Moon orbit, which turns out to be approximately a 38 hour one way trip. And for once the ticket prices are not exorbitant - $9000 for a cozy passenger berth, or $3000 per ton for cargo.

There is an important lesson here. What makes my other ticket prices so high isn't that spaceships are expensive, though they are, but that they are so unproductive, only delivering a few passenger and cargo loads per year, if that. For short trips with rapid turnaround the cost of space transport (under these assumptions) falls to levels comparable to global first class air travel.

This is another argument for settings that involve local space travel, such as Earth orbital space, or for that matter Saturn orbital space.

Moving right along, a few more sims. A 4000 ton ship fitted with a 1000 ton, 10 GW drive is just barely able to reach Saturn in 180 days, carrying only a nominal 5 ton payload. Extending travel time to 200 days yields a more practical ship, though a ticket still costs $25 million. If you're willing to take a year to get there, Saturn can be yours for less than $10 million, and the freight charge is a mere $300,000 per ton.

Finally I stepped the techlevel up another jump, to 100 gigawatts - verging on the low end of the torch range here. This is sufficient to reach Saturn in 90 days, with a peak speed above 270 km/s - nearly 0.1 percent of the speed of light, nothing to a photon but a lot for you and me. (I cut the energy cost by a factor of 10 too; the energy bill for that kind of speed was still most of the cost of the ticket.)


So there you have it. Go play with it, and see what results you come up with. Here's the link again: Rocketpunk Manifesto Travel Planner. And a recent post on getting to Saturn, among other places.

Image of the ISS from Astronomy Picture of the Day.


Update: The download is being a bit glitchy. I've tried renaming the file and re-uploading - let me know in comments if you're able to download it now.

Update II: Link fixed, thanks to Winch of Atomic Rockets. (See comments for brief, embarrassing explanation.)

49 comments:

Stevo Darkly said...

It sounds very cool! But when I click on the link, I am notified that "Internet Explorer cannot display the webpage."

I tried going to the Observatory page and clicking on the Travel Planner from there, but could not find it.

Weep. Wail.

-- Stevo Darkly

Will said...

As Stevo said, no joy in accessing the spreadsheet, which makes me sad :(

Stevo Darkly said...

Tried again. No luck yet.

To smoothly buy yourself some time, maybe you should recast the intro of the post to: "Coming soon! The handy Rocket Manifesto Travel Planner!" :)

Gotta grab dinner. Will try again later tonight.

Winchell said...

Ummmm, I think the link to the sheet is
http://www.rocketpunk-observatory.com/RM-TravelPlanner.xls

NOT

http://www.rocketpunk-observatory/RM-TravelPlanner.xls

Rick said...

Ouch - that was it. Stupid hand coded HTML fail #1: Learn URL basics, at least for my own damn site.

Thanks, Winch.

The link should work now. :-)

Jim Baerg said...

The flat space approximation is OK for BOTE calculations, but it *will* be off for many of these cases. The acceleration due to the sun's gravity at 1 AU is 0.6 milligee so for the 1st example of a trip to Mars with drive acceleration going from 0.62 milligee to 1.38 milligee, the curvature of the path will be substantial.

Similarly the Moon trip will start as a spiral outward from LEO until the spacecraft is close to earth escape speed.

Years ago I wrote a solar sail simulator. Maybe I could find the time to modify it for simulating an ion drive.

I haven't played with this much yet, but I wonder how much the cargo & passenger cost depends on that 'annual' cost. If annual maintenance is a small fraction of the capital cost & spacecraft last many decades we could see some odd economics in which a paid off spaceship becomes a very lucrative 'cash cow', similar to the way a decades old nuclear reactor can produce electricity for very low cost.

Thucydides said...

I suspect that the situation will be even more extreme when comparing passenger and cargo traffic.

Most cargo needs to have high "throughput", but probably has very little need for environmental support. This suggests that most cargo will not be carried on the 22nd century equivalent of a container ship, but rather as a stream of cargo containers fired into interplanetary space by mass driver or skyhook.

Passenger traffic will be the equivalent of today's huge cruise liners rather than fleets of Boeing 737's. The capital costs of building these ships will be the entry barrier against new companies.

Neofuel (http://www.neofuel.com/) suggests a fairly simple means of overcoming this cost barrier using a giant tire shaped bladder filled with water ice as the body of the ship (and the center cavity filled with the engines etc.) While each individual ship can only make a trip every few years, the large hulls can be made quite cheaply (but the engines obviously less so).

BTW, what version of EXCEL is being used here? I can get it to download but not open.

Rick said...

The flat space estimates are indeed strictly a BOTE approximation for real world trips. There does not seem to be any handy online sim for the steep orbits available to high Isp ships. And the orbits are complex, because the ship is under power half the time, during which its orbit is constantly changing.

The used spaceship market is just one of many economic variations hidden beneath these generalized figures. For example, the passenger ticket price is for the full cost of the trip, under the given assumptions.

But real tickets are sold by marginal cost. Passenger cabins and life support make the trip, and have to be paid for, whether there's a passenger in the cabin or not. The direct cost of the passenger, in extra propellant and food/air consumption, is something much less than averaged total cost.

Cheap 'standby' tickets will fall toward the marginal cost, and sometimes below it. If the spaceline is lucky they make it up by charging VIP passengers their firstborn child; otherwise the line goes broke, and another ship is available on the second hand market.

Historically transportation has always had peculiar economics, and usually highly politicized economics, because transportation is the vehicle of power. Who is actually paying for the tickets may have only a remote connection to who is riding in the cabins.

Rick said...

This is a really old Excel release! Excel 97. I have no idea whether the current release supports it, though it ought to!

Anonymous said...

Hmmm...these ship/trip sims look like they were made to check the perforamce of different combinations of mission module-command/hab-power/propulsion modules...I need to play with it for a while, but it looks like a good tool to help someone write a space trip story. BTW, how does this sim handle high powered fission sub-torches, like NSWR or that fission sail thing I ran across a few weeks back?

Ferrell

Eric said...

@ Rick & Thucydides,

.xls format is fully supported by all later versions of Excel (I don't know about the 2010 version, but it still should work there).
I downloaded the file and it's working just great in Excel '07.

Rick said...

Cargo may well travel by other means, mass drivers, laser boost, etc. Generally these replace mobile drive engines by fixed power plants at each end, so that all that makes the trip is the cargo, a pod, possibly a block of laser propellant, and some small control package.

If you are using mass drivers, the process of catching and decelerating inbound cargo pods will be ... stimulating.


In this group of sims I was zeroing in just on the power plant, seeing what missions a drive of given rating could perform. But you can sim to fit several parameters, to see what an overall ship configuration (drive, tankage, payload) can do.

The sim is very non-specific about the drive engine - you should be able to plug in NSWR or similar drives, even Orion.

One thing I found out is that Saturn is a LONG ways away. Even with a torch level drive putting out 1 terawatt of power, pushing you along at up to 85 milligees, with a peak speed over 600 km/s, it took 42 days to reach Saturn with a minimal payload, 60 days with a more substantial payload.

kirkspencer said...

I thought I was going to challenge an assumption and instead wound up independently supporting.

I thought the cost of construction (1 million per ton) was high. I decided I'd see what nuclear missile submarines cost per cubic meter of volume. $250-300K per m3 is the ballpark. I then decided to see what jumbos cost by volume. $210-250K per m3 -- close enough to call it 'normal'.

Citizen Joe said...

I'd like to see some other variables factored in. Starting orbital distance, ending orbital distance, central mass (typically the Sun). From those you can calculate your start and end orbital velocities and the effects of gravity. I'd also like to see start and finish velocities, probably as tangential and radial speed vectors. That would allow for multi-stage simulations.

Winchell said...

For orbital mechanics, if one can program in the Python language, you can use Erik Max Francis' BOTEC package.
http://www.alcyone.com/software/botec/

You can make "pork chop" plots with Jaqar's Swing-By calculator
http://www.jaqarsoftware.com/swingby.html

http://www.projectrho.com/rocket/rocket3b.html#porkchop

Byron said...

It looks good to me, except for one quibble. You used departure mass again! This just bothers me some, as it really is arbitrary, and you'll do design based on payload, dry mass, and deltaV, and get remass based on that. I'll try to think up alternate rating schemes, and propose them. It's a bit harder than for ships.

Rick said...

Welcome to another new commenter - Kirk is the eponymous inventor of that scourge of expensive missile buses, the kirklin mine.

A true orbital sim is waaay above my pay grade. There is no simple, elegant solution for these steep orbits the way there is for a Hohmann, and especially the combination with modest acceleration.

Well, actually it can be done by brute force, numerical integration second by second, or in chunks of X seconds for faster running at reduced precision.

The real problem is like the problem of space flight in miniature. An easy to use orbit sim would be a bear to write, and no one has put one online because the demand is very limited.


Cost per volume is a handy reference benchmark, because at least for hab sections volume is what we are paying for. I assumed an average hab density of 0.25. The ISS is more heavily built, 370 tons for 837 m3 of volume, a density of 0.44.

Fuel tankage volume, in my model, is much cheaper, about $7000 per cubic meter, but tankage is a very lightweight structure.


Departure mass: It isn't really arbitrary, because it represents the mass of your ship as fully loaded and ready for a mission.

That said, I could as easily have started with payload, and let the worksheet calculate departure mass. But you can fiddle a design to get a desired payload, much as I fiddled to get a 1000 ton, 10 GW drive.

Byron said...

I understand, but what I'm saying is that nobody will design that way.
Rating starships is hard. My guess is that a set of "standard trajectories" will be in place, such as the ones in the travel planner. Ships will be rated based on how many tons of payload they can take on such trajectories, meaning that both thrust and ISP play a part.
I'm trying to work out the math for the brachistochrone with fuel burn, but it's going to take a while. (Whenever the calculus starts making sense.)

Thucydides said...

Cargo can be very simple to ship (but calculating flight times might be very challenging indeed). I think one of the economic hot spots in the late 22nd century might well be the interplanetary futures market, matching supply and demand across months, years or even decades (a one tonne bottle of 3He might take a loooong time to hit the market when inbound from Uranus)

That being said, the imperative for cargo will be to ship and handle as cheaply as possible. Whatever you are going to send must fit into the standard cargo pod, require minimal environmental support and use the standard interface if it does require some sort of environmental or computer support in flight.

Launch by some sort of momentum transfer system minimizes the need for engines, and the cargo pod can deploy a solar, magnetic or electrostatic sail for fine tuning the orbit and to accelerate or decelerate to the market orbit (Obviously high tech goods coming from Earth or Cis Lunar space to a deep space destination will need to accelerate in order to reach customers before becoming obsolete).

If the pods are totally unpowered, then some sort of mass catcher must be in place, but the mass driver/mass catcher or momentum transfer tether will be a huge object, and space civilization will accumulate along the flanks like barnacles (habitation pods, power stations, factory units, the local port authority docks, Space Navy facilities, banks, futures exchanges, warehouses, seedy bars...). If the momentum transfer device is large enough (i.e. can outmass the object receiving momentum by an order of magnitude) then even the large interplanetary liners might take advantage of them for launching and final deceleration; a big saving in cost since engine power, fuel and remass can be correspondingly less.

Anonymous said...

Thucydides: so, if I understand you right, you're saying that we should build 'catapults' all over the Solar System to launch and catch cargo and passanger transports, with only specialized craft having large engines. The other ones would only have small, or nonexistant, engines for emergencies.

Ferrell

Byron said...

I got the brachistochrone sheet working. As I'm not sure how to post a spreadsheet, I'm sending it to Rick, and I'll email a copy to anyone who wants it. It's not user-friendly, and I'm new at this, so I make no guarantees.

Thucydides said...

Ferrell,

I am almost certain that will be the way economic development and large scale settlement will come about.

The limited numbers of large powerful engines will be the sticking point in any shipping scheme. If the same amount of energy is available in some sort of base station (mass driver, momentum transfer tether, laser launcher etc.) it can be used to deliver far more cargo, passengers etc. The costs can be amortized over a far greater number of passengers and cargo pods, bringing prices down to reasonable levels.

Scientific ships, military craft and "executive" transports are examples of ships which will need powerful engines for independent missions, but even then they can still make use of momentum transfer to reduce the amount of energy and remass required to start (or stop, depending on which way you are going). A book on space tethers (The Space Elevator: A Revolutionary Earth-To-Space Transportation System) has some calculations that indicate a billion ton tether made from fullerines would be able to lift a 700 ton spacecraft from the surface of the Earth and put it on a minimum energy transfer orbit to Saturn, enough of a starting impulse to enhance the performance of any drive, particularly if the actual target was closer (say Mars or Jupiter).

This isn't to take anything away from Rick's work on the spreadsheet, but to show there are other ways to get from point A to point B.

Rick said...

I tried redoing a worksheet to make payload a user input, but it turns out a lot harder than I thought. Which is probably why I didn't do it in the first place.

The problem is that starting with payload seems to be an inherently iterative process - as you add fuel, you must also add tankage, keel, and drive, and there doesn't seem to be a straightforward formula to account for the resulting tail chase.

Working the other way, from departure mass down, provides for these structures first, and 'whatever is left' is payload.


I'll have to take up the cargo discussion in the morning!

Citizen Joe said...

You know, I bet a nomogram could be made that has all those variables. I suspect that a couple variables would need to be constant, i.e. multiple nomograms. My guess is mission objective (Earth to Saturn) and engine type (with Isp and thrust ratio).

Rick said...

Cargo: There are 2.5 technologies, that I know of, for throwing the luggage across the Solar System: 1) mass drivers; 2) tethers, and 2.5) laser boost. It only gets a half point because the canisters must carry a block of solid propellant, though the energy comes from an external laser zap.

All of these are fairly 'slow' by space standards, but as Thucydides notes, this is not a problem for freight so long as it has a predictable demand. Mass drivers and laser boost also (probably) favor lots of small shipping canisters, launched in a steady stream, versus jumbo pods.

I don't think these techs are suited to passenger service, since long travel times mean not only excessive thumb twiddling but added life support requirements. Also, mass drivers would probably involve beaucoup acceleration. The less sensitive the freight, the better.

The economics of these techs are very uncertain, though it seems that they should be cheaper than ships, at least for steady commodity freight. The 'drive engines' are not mass constrained, and they can be operated and maintained by transport-nexus stations. The greater (and steadier) the traffic volume, the greater the probable advantage.

These techs, and for that matter ships, benefit from multiple travel destinations, because space traffic between any two planets (or asteroids, etc.) is very seasonal, even for high performance ships. The more potential destinations, the less often that either launch stations or ships will sit idle waiting for a launch window.

Byron said...

Also, they seem poorly suited for passengers because of payload. Long-duration ships will want to be big to give passengers options, but I don't think mass drivers will be configured for anything more than a couple dozen tons.

Rick said...

That, too. Tethers are different, since I think they may favor big loads.

One side note about mass drivers is that they lend themselves to spectacular accidents, especially if arriving loads don't quite line up. :-)

Byron said...

I figured out the answer to the puzzle of total mass from payload mass. Overall ship mass and fuel mass can be calculated from the following formula.
M=R*P/(1-(T(R-1)))
where M is mass, R is mass ratio, P is payload mass (anything that's not fuel or tanks), and T is tank fraction (percent of fuel mass).
If you wish to add a fraction that scales with total mass, such as an engine, E, use the following:
M=R*P/(1-(T(R-1))-(E*R))

Rick said...

Another formula to play around with!

In my current formula, drive engine mass is scaled to all nonfuel mass (i.e., 'arrival mass'). Which is somewhat arbitrary, but on one level any such formula is necessarily arbitrary!

Albert said...

Meh. A little competition is always good.

This is what I made up to play a little with the formulas on Atomic Rockets.

Spreadsheet, Excel version
Spreadsheet, Open Office version
It should allow you to build a VASIMR ship to go wherever you want.

With a little modification (that any tinkerer will grasp in seconds) it can work for most other engines as well.

Although this doesn't look easy as Rick makes it appear.

Either I have made some stupid mistake somewhare (never turn your back on this spreadsheet, it stings :), or I'm missing his assumptions.

Oh, btw, I take no responsibility for space mission failure if you use the linked spreadsheets.

Byron said...

It looks OK, but you used total mass. I may have to fix that. Then again, I have my own ships which are slightly higher-performance.

Rick said...

Some of my assumptions are solid (i.e., based on physics), but others - such as drive mass - are engineering rules of thumb, and pretty arbitrary. For example, expressing drive mass as a fraction of nonfuel mass is a rough way of saying how much of the (unfueled) ship is given over to the drive engine. It is merely a thumbnail way to say 'high performance' if the ship is largely drive engine, or lower performance if the drive engine is (relatively) dinky.

Albert said...

Some of my assumptions are solid (i.e., based on physics), but others - such as drive mass - are engineering rules of thumb, and pretty arbitrary.

I should have been more clear.
My spreadsheet seems unable to give better performance than around 0.5 milligee of acceleration if used with a VASIMR (that is the best NEP engine i can find) and reasonable assumptions on structural weight and tank weight. Even if the power plant weight is set to 0.


That's mostly an engineering concern and probably not exactly relevant here, but I think milligee acceleration is more the playground of self-powered propulsion, like fusion engines.
Not the 1-Gee fusion torches anyone expects, though.

After a few hours of tinkering with my spreadsheet I googled for realistic fusion engines concepts and I found this paper. (a very good read, has formulas for about anything you want to do with fusion or antimatter engines, mission planning too)
Comparison of Fusion-Antiproton Propulsion Systems for interplanetary travel

There are three fusion concepts that when ported in my spreadsheet seem to be capped at around 1.5, 2.2 and 6 milligee respectively.
(without me "shifting gears" manually decreasing exaust speed and increasing thrust)

Feel free to slap me for hiijacking this. :)

-Albert

Rick said...

No hijacking at all!

The problem may be simply that my baseline is a quite high power density drive, 10 kW/kg - the sort of thing I would indeed expect of a fusion drive, and more than VASIMR can deliver. I believe I have a couple sims labeled 'early,' with 1 kW/kg drives. Configured for Mars in 3 months it gets close to 1 milligee, but with a much lower specific impulse, around 5000 seconds (= 50 km/s exhaust velocity).

Generally, for a given drive power density, the longer the trip, the lower the optimum acceleration and the higher the optimum specific impulse.

Interplanetary travel at 1 g requires true torch drives, with power density upwards (probably WELL upwards) of 1 MW/kg.

Albert said...

The problem may be simply that my baseline is a quite high power density drive, 10 kW/kg

Which is around the power density of the fusion drive concepts I found. (although IC fusion concept has 110 kw/Kg)
From then on it's only a matter of tweaking Ve to get more thrust at the cost of delta V. And the IC fusion one has lots of Ve to spare.

Mistery solved. Thank you. :)


Btw, VASIMR still appears "highly dissatisfying" anyway, I had to cheat a lot to get something resembling milligees at 50 km/s of Ve. (not last keeping power plant mass at 0, otherwise I'd never get to the 1 Kw/kg checkpoint)
I'd really like to know what kind of of highly optimistic projections they used for that "3 months to mars" or somesuch hype of some time ago.

This the same spreadsheet as above, but with the fusion concepts bunched in.
Just in case anyone wants it.

-Albert

Rick said...

What is the drive power density of VASIMR? Your spreadsheet (and Winch's site) give drive mass as 10 tons + pp, but I don't know what pp is.

Albert said...

"pp" is power plant mass (there is a misplaced description somewhere in that page of Atomic Rockets).

A VASIMR weights 10 tons and eats 10 Mw, so its power density is 1 kw/kg.

But the power for it must come from somewhere. And most power plant's power densities aren't exactly helping.

At best you'd get a nuclear power plant with 1 kw/kg (according to Atomic Rockets). And solar cells are waaay worse.

So the whole thing together should at best be 0.5 kw/kg.
With a Sci-Fi 10 kw/kg power plant you get a 0.9 kw/kg drive section.

But I kept the power plant weight to 0 while trying to push it towards a milligee with 50 km/s Ve. And failed.

While I just bunched in the fusion engines from above and got around the same acceleration as stated in the paper.

-Albert

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Rick said...

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tonyon said...

...need hyperluminal SPEED and TIME of the Immortals (3D Bioprinting...Telomerase...) to conquer SPACE...

tonyon said...

...interstellar travel (Alpha Centauri C: 1g)... passengers climb in the space-elevator to the ship...awaits them in the asteroid Toutatis, which long ago placed in geostationary orbit... Day 1: zero-speed...distance = 40.68 Billion kms (4.068*10¹³)...total time travel = 1490 days (4 years and 1 month)... THE SHIP TAKEOFF►... 354 days to 1 G (9.8 mts/sec²) of CONSTANT ACCELERATION (weightlessness solved the problem), the ship with its powerful Antimatter rocket engines working tirelessly...antigravity fields generator run forwards working, and no collisions with anything...the ship reaches light-speed and...disappears...to enter into "superluminal dimension"...and still traveling at superluminal-speed > 1c... Day 745 (2 years and 15 days): the ship reaches the halfway...maximum superluminal-speed = 2.1 c..."ladies and gentlemen please belts, for a few minutes while the motors are Off will be in weightlessness during the maneuver"...the ship rotates 180ยบ around its "vertical" axis (perpendicular to the longitudinal axis of momentum)...On engines again and...◄starts to brake... Day 1136: the ship slows light-speed and...appears...descends again to the "subluminal dimension"... 354 days more decelerating and the ship is at zero-speed, the passenger disembarks at destination, a planet of Alpha Centauri C.

tonyon said...

...interplanetary travel (to the asteroid of the end of the world)... asteroid Toutatis...how to move a mass of 40,000 million Tm?. Obviously the chemical rockets are not useful. Only a few nuclear charges will be enough for gives it the shove. At Space, on having not air, there is not expansive wave. Only will arrive to it the radiations, gamma rays, etc, which volatilize the impact surface of those radiations and eject the superficial material as a jet propulsion. Subterranean nuclear charge: destruction of the asteroid. Nuclear charge very near from the surface: deflection of the asteroid. If asteroid it is small, as DA-14, perhaps being enough with a single nuclear charge...or less drastic for give them thrust: to install on asteroid a nuclear electric generator. A spatial-catapult, as the aircraft´s carrier deck but with a linear electric motor, some over rails tip cars, or fastened to an endless belt, launching rocks and/or plastic bags filled with ground.. A spatial-sling, a revolving tube at high revolutions, rocks entering by the gyration axis and go out by the tube sent away at big speed towards the Space... Thrust by action/reaction for deflecting it with time... If asteroid it is large, as Toutatis, probably would be necessary a few stepped nuclear charges for moving it. War ballistic missiles that there are, they are not useful, are designed for go away from continent to continent... Only can be useful a rocket that can to put the charge at interplanetary orbit, as the multi-phase which put satellites in geostationary orbit (is necessary have them already prepared in a Spatial-Command with all the nuclear weapons that there are in the World controlled and preserved by an International Organism, only for that)...("Doomsday asteroid": W. Cox and H. Chestek). Not only will can deflecting them from their trajectories of collision with Earth, but besides...they will be placed in geostationary orbit for to exploit their wealth of minerals, water, oxygen, nitrogen for the air and agriculture of Vital Support Gardens, etc. They will be utilized as ships, for to travel in them to the Solar System boundaries...as a "buses" fleet, going over there in one and if want to return or go away to other direction await the approaching of suitable asteroid to transferring... Drilling them by the center, as a gyratory without bone olive, with a fusion reactor in the center which it will gives the light and heat as an artificial sun... Immense subterranean Gardens which will produce the air and food... At to look over there at high...will see to those other cities "downwards head"...

tonyon said...
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tonyon said...

3D Bioprinting...will arrive in time for us the Fantastic Voyage towards the Immortal Future?...

tonyon said...

...future travel (without false freedom)... Silence is golden?..."rossse-tie" passive homo-vice, "bluesss skysss-tie" active homo-vice from the "facestifffinger". The apostles of the inhuman homo-vice, with their propagator acolytes "maricones" and "tortilleras" in news TV installed announcing "happy" their days of "pride", infecting colors, numbers, words... Nobody yet perceives what it pretend the fetid homo-vices with from technology use degenerated: go artificially pregnant and throw their "sons" by where go out the fetid excrement to that unworthy and horrible ill world, a world without women where nobody will can live with dignity. Homo-vices, religious, have the control of all Global Media: Internet, TV, radio, movies, newspapers...see, besides of look, constantly in Hollywood-movies, South American TV-novels and TV programs role of evilness against beautiful innocent actress, role of "goodness" for man-actor, violence, crime and insults against women, for that after will be reality passing from fiction to real life (what´s to see, is what´s to do). And nobody in the entire World says anything, nor do people, nor do politicians, nor do nobody. Only hypocrisy and lies and silence, with "marymales" occuppying almost each National Presidency reclaiming "free sex orientation"...because if anybody says anything does not can have a job, or something worse... Silence is golden?, NOT. It´s time for to say the truth, for the wellness of Future´s Humankind.

tonyon said...

...apollo missions cancelled... Only are in Earth´s "culture" religion gods, for that reason ½ century ago without go to Moon...religious have very fear from extraterrestrial...because innocent people also will know this.

tonyon said...

...3D Bioprinting-Immortality (biological timers)... Forever young with modified Biological Timers...which are the biological timers?, where are them? (genes, hypothalamus...), how functioning them?, how can modify them for maintenance the hormone´s production, enzymes, cellular regeneration...all Eternity at same level of the 18 years old?... Have to accelerate Research about Memory and the Space´s Colonization... Immortality comes...

tonyon said...

Nobel Prize physiology 2017...about biological timers...