Space Flight

[Curran]

I watched the google video the other day, and the author was talking about space flight time to Mars of a month, and to Titan in 78 days. That sounds great, but the question I have, can this technology be used to build a space craft that can leave from the surface of the Earth in a single stage? What are the possibilities?

[Adam Whistle]

Link to the video please?

The problem is, that I don’t think there is anyone drawing blueprints for fusion engines, at least not until the thing has been demonstrated as an economical power plant.

The only guy that is working on fusion space engines that I know about, is this guy: http://luke.eng.uci.edu/ahcheung/
There is a paper there about it.

And single-stage? The best option if you want to have single-stage, is to have two engines: one for landing and taking off with high thrust, another for outer-space flight with high specific impulse.

[DaveMart]

That would be the Bussrd engine – there is a video on Google
Here is a link to the article :
http://www.ibiblio.org/lunar/school/InterStellar/Explorer_Class/Bussard_Fusion_systems.HTML
I don’t think it is designed for take off from a planetary surface, so far as I remember.

[Adam Whistle]

Because its an explored idea and it isn’t designed at all. Designing would involved blueprints and a craft to put the thing on.
EDIT: Although, there is enough thrust to allow it to accurate speed faster then gravity, so it could take off.

[AaronB]

While the blueprints may not be on the table, the idea of using the dense plasma focus (the reactor for focus fusion) for space propulsion is not new. See https://focusfusion.org/index.php/site/article/university_of_illinois_space_propulsion/. Focus fusion would work for propulsion, but you need a big power source for it. If we can get the fusion reactor to produce net energy, then you could use one reactor to generate electricity, and another one as the rocket, or some sort of setup like that.

[Adam Whistle]

Well, yes, there is the “torchship” idea (a spaceship that has an engine with both high Isp and thrust), but a more realistic idea is to use Focus Fusion as a power plant, to power the electric or plasma engines such as VASIMR, Ion propulsion, magnetoplasmadynamic thrusters, etc. Charged particles can be guided into hydrogen to get high thrust at the expense of Isp, although I fear that there may be some radiation (most likely low enough to be not more of a concern then a chemical engines exhaust).

As a curious note, space engines using fission has been planned and even tested a long time ago, called Nuclear Thermal Rocket. This scheme is fairly safe, as it only uses the heat generated by the fission reactor, and has twice the amount of Isp then what chemical rockets can possibly archive , while still having enough thrust to get out of Earth’s gravity well (especially if you put LOX into the hydrogen exhaust).

[Glenn Millam]

One of the things I’ve wondered is, if you can build a spacecraft that uses focus fusion as its main drive, why couldn’t you also use a DPF power plant solely for generating a magnetic “force-field” for shielding the spacecraft from radiation, similarly to the way Earth’s magnetic field shields us? Sure, it would make the spacecaft much larger, but, who cares? Space is big. While you are at it, why not have another for rotating the living quarter to provide artificial gravity so that calcium doesn’t leach from bones and muscles don’t atrophy?

[pktanz]

the link isnt working for me ..

[pktanz]

opps, it worked. Nvm.

[Jolly Roger]

Glenn Millam wrote: … why couldn’t you also use a DPF power plant solely for generating a magnetic “force-field” for shielding the spacecraft from radiation, [similar] to the way Earth’s magnetic field shields us?

The “force field” you speak of is the Mini-Magnetospheric Plasma Propulsion (M2P2), which can provide both shielding and propulsion.

http://www.ess.washington.edu/Space/M2P2/

Also, here is a “parent” page on Advanced Electric Propulsion that has links to the M2P2 and related devices such as a plasma thruster.

http://www.ess.washington.edu/Space/propulsion.html

… why not have another for rotating the living quarter to provide artificial gravity…?

The living quarters can be rotated on a magnetic bearing (no friction), so after initial spin-up, maintaining rotation will need minimal energy. It will not require a dedicated power supply. It can be tapped off the shield or main propulsion reactor.

[Transmute]

Why not just use the DPFs to propel a very larger ship with water tank shielding and enough space for artificial gravity?

Lets be realistic here: a DPF is not a vonder engine, sure its has a ISP between 100,000-2,000,000sec but its does not have much thrust, this makes it great for speeding from planet to planet but a DPF could not “take off” from anything larger then an asteroid. So DPF does not answer the hardest problem there is in space travel: getting off the earth. Unless of course you use some DPF powered laser/maser array to

[Jolly Roger]

Transmute wrote: Why not just use the DPFs to propel a very larger ship with water tank shielding and enough space for artificial gravity?

Water is heavy. We need to keep the mass down, as the higher the mass the lower the acceleration applied to the ship by the engines. Though we will have some water shielding to protect the crew from neutrons, a much lighter magnetic bubble (such as M2P2) will deflect the charged particles of the solar wind. If the bubble is large enough (many miles) the solar wind can propel the craft.

Artificial gravity can be generated aboard a small craft by revolving the crew’s quarters on a counterweighted tether with a radius of at least 730 feet. See SpinCalc
http://www.artificial-gravity.com/sw/SpinCalc/SpinCalc.htm

… a DPF … does not have much thrust, … a DPF could not “take off” from anything larger then an asteroid.

A DPF does not throughput very much mass and is therefore not good for a rocket engine directly, but it could function as the power source for a High Power Helicon (HPH) plasma thruster, VASIMR or M2P2.

High Power Helicon
http://www.ess.washington.edu/Space/HPH/

Note that a VASIMR and M2P2 may not be able to function at the same time, but a VASIMR may be able to be configured to function as an M2P2.

One suggested application of the HPH is the MagBeam in which it is used as a “plasma cannon” aimed at a M2P2-equipped craft to push it to a higher orbit. The “cannon” platform would have to be substantially more massive than the craft to be pushed.

(Personal speculation – could the polarity/frequency of the MagBeam beam/field be adjusted to create a “tractor beam”?)

MagBeam
http://www.ess.washington.edu/space/magbeam/

[Transmute]

Jolly Roger wrote: Water is heavy. We need to keep the mass down, as the higher the mass the lower the acceleration applied to the ship by the engines. Though we will have some water shielding to protect the crew from neutrons, a much lighter magnetic bubble (such as M2P2) will deflect the charged particles of the solar wind. If the bubble is large enough (many miles) the solar wind can propel the craft.

Of course water is heavy! But when you have 1million ISP engines you can have a battlestar galactica ship worth in shielding with massive engine arrays and still travel to pluto and back with only 10% of you mass in fuel! Have you read the Scientific American article on spaceship shielding?
Basically a magnetic shield would be a gross hazard for the crew, would require a large cryogenic support structure and expensive superconducting magnets. A magnetic bubble would require fuel (to be plasmafied) and though it could shield against solar wind it would be useless against high powered cosmic rays.

Artificial gravity can be generated aboard a small craft by revolving the crew

[Brian H]

Given the electric output from the FF, ions of any description could be accelerated from a separate rocket device. The thrust you get is the power output of the FF reactor X the efficiency of the ion thruster.

The Bussard can never operate in atmosphere, or at low speeds. It depends on collecting hydrogen over a wide swath as it accelerates through space. It needs a kick-start to get up to ignition velocity.

Read Tau Zero, by Poul Anderson, if you can find a copy. The driving force in the (short) novel is a Bussard that can’t be shut down.

[Author]

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