A mission to reach 1% of the Speed Of Light

[Rockhem]

Is reaching 1% of the speed of light possible with our current technology, it is 300 kilometers/second.

Maybe using gravity assists to help also, could make us go 1% the speed of light.

I just wanted to start a discussion on this.

[Themohawkninja]

There are plenty of books out there that talk about theoretical designs that can reach at most 10%, the lovely Cold War Orion project being one of them.

However, if by current technology, you mean and propulsion system that we currently use, yes, chemical rockets could do that, but you would probably need to burn all of the hydrogen/helium/etc in Jupiter to do so.

Now, if you want to define that as (which is what I assume you mean) practical designs that we currently use, an ion drive with enough fuel might do it. I'll run the math to see how much Xenon you would need.

EDIT: Okay, I punched in the numbers for the Dawn spacecraft into the rocket equation via Wolfram Alpha, and began to mess around with the amount of fuel. It would take over 1,184,000 kg of Xenon gas to get to 1% the speed of light. Now, I got this just be altering the initial mass of the vehicle, and due to the fact that the vehicle would have to be much larger than Dawn to hold all of that gas, than the amount of fuel would increase even more.

Now for the part that makes that ~1.2 million kg of fuel seem really impractical. At $120 per 100 grams, that puts the price (on fuel alone) to be $14,208,000,000.

EDIT 2: Yeah, PakledHostage is right, the speed of light is 300,000 km/s, so 1% of that is 3000 km/s. I don't feel like doing the math since you can imagine how crazy the fuel and cost requirements would be.

Edited July 13, 2013 by Themohawkninja

[PakledHostage]

Is reaching 1% of the speed of light possible with our current technology, it is 300 kilometers/second.

I don't want to pick nits, but I thought I should point out that you're out by an order of magnitude. 1% of the speed of light is almost 3000 km/second.

[Spartwo]

well voyager1 is traveling at 17.46km/s

[jwenting]

Buzzard ramjet could be built, or solar powered laser boosted solar sails.

You'd get there, just would take quite a while.

Of course there are some engineering "challenges" in building both, but no theoretical impossibility and the technology exists to do it, even if it's never been employed on the scale you'd need.

[UmbralRaptor]

3000 km/s? That'll make gravity assists (aside maybe from a sundive) of negligible value. No currently available technology (read: <10,000 s ion engines) will get you those kinds of speeds. I'm not sure how much development would be necessary for a system that can (eg: fission fragment rocket, ultra high Isp Orion, starwisp or other beamed propulsion. I'm unsure if solar sails would cut it)

Buzzard ramjet

Bussard, and mind the drag.

edit: After running some numbers for a 0.1 AU sundive, I'm only seeing at extra ~100 km/s. That's... less useful than I was expecting.

Edited July 14, 2013 by UmbralRaptor

[Nuke]

feep could do 10000s, and is flown on science sats. but you will need to wait a very very long time (micronewton thrust).

[WestAir]

Just open the ships window and throw rocks out the back until it pushes you to 3,000km/s.

You could also just look deep into the cosmos, realize that trillions of stars - even entire galaxies, are flying by you at speeds greater than light. Once you accept the concept that it is you who is accelerated past light, and not the brilliant and infinite number of galaxies in the open horizon - you'll realize you've been going faster than 3,000km/s all along and you won't need a $2 billion dollars worth of Xenon Gas and ion thrusters.

/win

[metaphor]

It's still impossible with 10,000s Isp. Even with a rocket where the fuel weighs 1 million times the mass of the rest of the rocket, you would only get 1400 km/s delta-v.

[magnemoe]

Buzzard ramjet could be built, or solar powered laser boosted solar sails.

You'd get there, just would take quite a while.

Of course there are some engineering "challenges" in building both, but no theoretical impossibility and the technology exists to do it, even if it's never been employed on the scale you'd need.

An bussard ramjet would be very hard to build. First you must be able to do H2 fusion.

Now an normal fusion engine itself should be able to reach this speed. An laser boosted solar sail would be nice for an small probe.

[Nuke]

obvious question, how does pointing a laser at a solar sail and bouncing it off differ from just pointing the laser out the back? seems either way would give you the same thrust (practically nothing).

[Scotius]

Well, in this case you only need a sail and a probe. If you are taking laser with you though...it will have to be massive - both in size and weight. And it will require power source. And a fuel for the power source. And control systems for all that. And...you get the idea.

[Justy]

obvious question, how does pointing a laser at a solar sail and bouncing it off differ from just pointing the laser out the back? seems either way would give you the same thrust (practically nothing).

You're right. So instead of a pitiful laser pointing out the back of the spacecraft, you leave a gigantic laser at Earth, powered by solar panels and nuclear reactors and hydroelectric dams and windmills and natural gas and steam engines and hamster wheels and everything else, with no regard at all to how much it weighs, because who cares, it's not going anywhere. Then you point the laser at your very, very light solar sail spacecraft. Now you can use a laser putting out a thousand times practically nothing, and as long as the power supply keeps up on Earth (note to self: start hamster breeding program), you can keep it up for a very long time.

On second thought, you probably don't leave it on Earth, you leave it in Earth *orbit*. You can't afford to lose laser output as heat before it leaves the atmosphere. So I guess we're down to solar and nuclear power only (note to self: hamster spacesuits). But still, not having to accelerate that power supply and giant laser is a big deal.

[Themohawkninja]

To get a solar sail going this fast via lasers, won't we need a laser with a power in the order of petawatts or even exowatts?

[Person012345]

3000 km/s? That'll make gravity assists (aside maybe from a sundive) of negligible value. No currently available technology (read: <10,000 s ion engines) will get you those kinds of speeds.

Nuclear pulse propulsion?

[Person012345]

To get a solar sail going this fast via lasers, won't we need a laser with a power in the order of petawatts or even exowatts?

Top speed is not dependent on thrust value. You could fart out the back of your spacecraft for long enough and reach near light.

If you mean practically in a human lifetime then I don't know. >.>

[andrewas]

Thats true with self-contained drives, but not with laser sails. Beam dispersion means you deliver less energy to the sail as it gets further away, so long, slow acceleration is much more expensive than a short, fast acceleration.

[Person012345]

Thats true with self-contained drives, but not with laser sails. Beam dispersion means you deliver less energy to the sail as it gets further away, so long, slow acceleration is much more expensive than a short, fast acceleration.

Fair enough.

[UmbralRaptor]

Nuclear pulse propulsion?

Maybe:

I'm not sure how much development would be necessary for a system that can ... ultra high Isp Orion

Note that you have to be careful to optimize the pulse units for Isp.

[jwenting]

Top speed is not dependent on thrust value. You could fart out the back of your spacecraft for long enough and reach near light.

If you mean practically in a human lifetime then I don't know. >.>

correct. And build them in solar orbit inside the orbit of Venus, you have plenty of power to work with.

As I said, engineering challenge. Big one, but can be done.

And the sails themselves ditto. We've some working versions, but ideally would need to get them a lot thinner (and thus lighter) than we are making today.

[Sliinty]

Just open the ships window and throw rocks out the back until it pushes you to 3,000km/s.

You could also just look deep into the cosmos, realize that trillions of stars - even entire galaxies, are flying by you at speeds greater than light. Once you accept the concept that it is you who is accelerated past light, and not the brilliant and infinite number of galaxies in the open horizon - you'll realize you've been going faster than 3,000km/s all along and you won't need a $2 billion dollars worth of Xenon Gas and ion thrusters.

/win

Read special relativity and then cry.

EDIT: admittedly they will be going over 0.01c, that's for sure, but c is the max no matter your frame of reference.

Also, 10000s isn't nearly enough. Not accounting for the effects of lorentzian transformations etc, as (1-3000000^2/300000000^2)^0.5 is still 0.99995, so we wont see any change within a few sig fig, if we have a reasonable mass fraction (say 100), you still need well over 60,000s. Maybe someone try hacking an engine with 150,000s, That could do with a mass fraction of under 10.

Edited July 15, 2013 by Sliinty

[TheSaint]

Project Daedelus was supposed to reach 0.12c for a trip to Barnard's Star:

http://en.wikipedia.org/wiki/Project_Daedalus

Project Longshot was supposed to reach 0.045c, but it was also supposed to decelerate at the other end and enter orbit around Alpha Centauri B. Only ~400 tons as well, I've assembled bigger ships than that in LKO.

http://en.wikipedia.org/wiki/Project_Longshot

Both of those were design studies using existing (or rationally postulated) technology by people with a lot more engineering knowledge than I have. So I would guess that it would be possible.

[RuBisCO]

Nuclear Salt Water Rocket is probably the most practical method we have with current technology. Next would be something like Project Orion, Deadalus and Longshot are even more questionable technologically. If we developed Fusion reactor engines though would work maybe up to as high as 15% the speed of light (If ISP as high as 1.5 million), but would likely have very poor thrust compare to the NSWR or Project Orions Nuclear Pulse. A Nuclear fusion spaceship averaging 1/1000 Gee thrust would take ~150 years to reach 15% speed of light, or 10 years to reach 1% speed of light. If your target was a star system of less then 10 light years you would spend longer accelerating then to reach your target: you would not be able to reach max speed before you had to decelerate.

A NSWR would have wicked acceleration, the baseline NSWR proposed would have twice the thrust of the Saturn V F1 engine! That is using 20% pure U235, I would guess an NSWR running on >80% purity plutonium might be able to have a minimum thrust of 1/20 that, but that is still 115 klbs or 650 kN, impressive for an engine that uses literally a few ml of nuclear fuel and a few hundred ml of water coolant/afterburner a second, we are talking an engine with a T/W of several hundred easy! Assuming an exhaust velocity of 1% the speed of light (ISP 306,000), say 10 MN thrust, a 3000 ton space craft would start off with 30% G thrust, by the time it reach 1% the speed of light would be 1000 tons and 1 G thrust, this would take only ~5.5 days! Of course now you would need to coast 460 years until you reach the nearest start system, then to decelerate that 1000 tons ship down, weighing ~350 tons in the end with enough delta V to dink around alot (600,000 m/s, assuming empty mass of 300 tons)

Edited July 16, 2013 by RuBisCO

[USNavyJHarris]

Barnard's Star was studied as part of Project Daedalus. Undertaken between 1973 and 1978, the study suggested that rapid, unmanned travel to another star system was possible with existing or near-future technology.⁽¹⁾ Barnard's Star was chosen as a target partly because it was believed to have planets.⁽²⁾

The theoretical model suggested that a nuclear pulse rocket employing nuclear fusion (specifically, electron bombardment of deuterium [D] and helium-3 [3H]) and accelerating for four years could achieve a velocity of 12% of the speed of light. The star could then be reached in 50 years, within a human lifetime.⁽²⁾ Along with detailed investigation of the star and any companions, the interstellar medium would be examined and baseline astrometric readings performed.⁽¹⁾

The initial Project Daedalus model sparked further theoretical research. In 1980, Robert Freitas suggested a more ambitious plan: a self-reproducing spacecraft intended to search for and make contact with extraterrestrial life.⁽³⁾ Built and launched in Jovian (Jupiter's) orbit, it would reach Barnard's Star in 47 years under parameters similar to those of the original Project Daedalus. Once at the star, it would begin automated self-replication, constructing a factory, initially to manufacture exploratory probes and eventually to create a copy of the original spacecraft after 1,000 years.⁽³⁾

Sources: (from the wikipedia article on Barnard's Star)

1. Bond, A. & Martin, A.R. (1976). "Project Daedalus - The Mission Profile". Journal of the British Interplanetary Society. 29 (2): 101.
2. Darling, David (July 2005)."Daedalus Project". The Encyclopedia of Astrobiology, Astronomy, and Spaceflight. Archived from the original on 31 August 2006.
3. Freitas, Robert A., Jr. (July 1980). "A Self-Reproducing Interstellar Probe". Journal of the British Interplanetary Society. 33: 251–264.Jump up to:Freitas, Robert A., Jr. (July 1980). "A Self-Reproducing Interstellar Probe". Journal of the British Interplanetary Society. 33: 251–264.Bibcode:1980JBIS...33..251F. Retrieved October 1, 2008.

 

[Ultimate Steve]

1 hour ago, USNavyJHarris said:

*snip*

Hello, @USNavyJHarris! Welcome to the forums!

Thank you for contributing this information to this thread. However, I would like to point out that this thread is from 2013. Posting in an old thread (Necroposting) is generally frowned upon here, but not necessarily forbidden. Just for future reference.

Welcome!