
The quest for a reactionless space drive - Digit-Al
http://boingboing.net/2014/11/24/the-quest-for-a-reactionless-s.html
======
dnautics
A really amazing, honest, and straightforward account from the grad student in
the lab.

[http://www.otherhand.org/home-page/physics/graduate-
studies-...](http://www.otherhand.org/home-page/physics/graduate-studies-in-
physics-at-cal-state-university-fullerton/)

~~~
cygx
_Some quotes from the end of the article:_

As time progressed and the experimental apparatus more refined, the “effect”
seemed to get smaller, and that’s a REAL bad sign. It was already well below
what the theory predicted. That sets off alarm bells. After all this time, if
something isn’t in hand to float around a table top, its should still at least
be producing unequivocal results.

I am aware of only one positive replication attempt, and even that
experimenter (Paul March) had concerns over its validity. All other
replication attempts have either been negative or ambiguous. My own
experiments were ambiguous.

It seems to make the effect happen, a lot of parameters for the test devices,
some not clearly understood, need to be “just so”. The question remains, are
the devices being dialed in to create a real effect, or do things need to be
just so to cause merely a false positive?

~~~
dnautics
it's (sadly) very refreshing honesty from a scientist. In grad school, I
counseled a junior grad student on this sort of phenomenon, she didn't take my
advice and learned a very hard lesson - spending 4 years of grad school
chasing down ghosts. On the other hand, it wasn't a waste, she got a very good
job in the pharma industry on the back of her commitment to sussing out
errors, her honesty and introspection.

~~~
tormeh
Given the potential upsides, I would say it's worth finding the errors in this
reactionless drive. Even if it turns out to be just a fantasy the poorly
understood effects that need to be "just so" might be interesting in their own
right.

~~~
jessriedel
That seems like a compelling position until you're exposed to a million such
cases. There's no end to the number of weird, malfunctioning pieces of
equipment or complicated many-body systems for which we have a theory that
sort of explains them with a few poorly understood wrinkles.

~~~
saalweachter
Yes, yes, a million times yes.

In a world as big as ours, it's reasonable to diversify your investments and
keep a few million to one long-shots going, but it's important not to lose
sight of the odds. Buy a lotto ticket every now and again, but put the bulk of
your money in a 401k or other solid investment.

In this case, I think we're giving this idea more or less exactly the right
amount of attention: one dedicated crank (and I use that term lovingly)
devoting his life to his crazy theory, and a handful of less invested others
occasionally checking in on it. If he can make it work, fantastic, if he
can't, well, we didn't waste too much on it.

------
tjradcliffe
Several points:

1) "Foundations of Physics" is closer to a philosophy journal than a physics
journal. It's full of fascinating stuff, but it's far more speculative than
any other legitimate journal. When libraries were cutting budgets in the '80's
and '90's it was generally the first to go.

2) When highly theoretical phenomena are talked about in engineering terms,
the odds of confirmation bias are huge. Who wouldn't want a reactionless-ish
thruster?

3) Measuring transient forces of the kind being applied here is extremely
hard, and the number of confounding factors is extremely large. The article
mentions a mu-metal shield, which will screen some of the Earth's magnetic
field from the apparatus but which is useless for screening transient magnetic
fields, which get generated by transient electric fields thanks to the magic
of Maxwell. Ampere's law tells us CurlB = mu_0 _epsilon_0_ dE/dt. So the
possibility of residual electro-magnetic forces is non-trivial to say the
least, particularly in a room full of conductors and time-varying EM-fields
(from the wiring, the pump, etc).

Putting the whole apparatus in a Faraday cage would help, but the history of
measuring small (and transient) forces in physics in the past couple of
decades (the fifth force mess, Joe Weber's coherent neutrino scattering work)
argues that we take these experimental measurements with a large grain of
salt, unless they can be shown to be in precise numerical agreement with the
theory's predictions over an order of magnitude variation in power input and
rate of variation.

The theory may not be wrong, but it needs a lot more experimental
investigation and likely theoretical examination as well. Theorists tend not
to spend a lot of time critiquing things that look really likely to be wrong,
because proving something that everyone thinks is probably wrong, wrong can be
incredibly time-consuming and utterly unrewarding. So the lack of theoretical
disproof is not very compelling. So far as I know Joe Weber's coherent
scattering theory was never dis-proven in publication, either: it was mostly
dismissed by informal but compelling arguments at conferences (the best one
was simply that there was nothing special about neutrinos in Weber's theory,
so if what he said was correct single crystals would coherently scatter x-rays
in exactly the same way, which would have shown up as an anomalous low-energy
contribution to EM cross-sections that would have been an obvious problem for
decades if anyone had observed it.)

~~~
baq
> Who wouldn't want a reactionless-ish thruster?

anyone who understands that it's a device for turning bricks into weapons of
mass destruction. not that a conventional nuclear reactor isn't one, it's just
that it uses more sophisticated bricks.

~~~
mikeash
You should check out these things called "rockets" that have been doing that
for many decades now.

~~~
baq
i don't know of a rocket that could effortlessly accelerate a rock to a
nontrivial percentage of c, which would be within a reactionless drive's
capability, given enough time. see also
[http://www.projectrho.com/public_html/rocket/reactionlessdri...](http://www.projectrho.com/public_html/rocket/reactionlessdrive.php).

~~~
oakwhiz
>effortlessly

A reactionless drive, if possible, would still require "effort" to produce
thrust in the form of energy. It is not a "free energy" device. The only
difference between a reactionless drive and a rocket is that a rocket must
carry its own fuel with it, so that it can expel the fuel to generate thrust.
The fuel adds additional mass to the whole rocket, so in a way, a rocket
requires extra fuel to carry its fuel. Since a reactionless drive does not
expel anything, a reactionless drive would not carry any fuel, and therefore
could be more efficient by way of lower mass, but it would still need to carry
an energy source of some type, such as a nuclear reactor, or a radioisotope
thermoelectric generator.

Rockets are certainly capable of accelerating a mass to a significant fraction
of the speed of light. However it is important to note that it becomes more
difficult to accelerate an object as the object gets closer to the speed of
light. You need more energy to add a constant amount of velocity as your
current velocity increases. This applies regardless of what kind of method you
are using to accelerate - doesn't matter if it's a rocket or a reactionless
drive. The difference is only in efficiency - it is thought that a
reactionless drive might be more efficient. However if a reactionless drive
really is possible, it might provide a lot less thrust than you think.

So even if reactionless drives are developed, they might be more efficient
than rockets, but far less timely. I think you'd be waiting quite a while for
the reactionless vehicle to attain any sort of appreciable velocity - perhaps
decades. As far as weapons go, humans have not met any aliens yet (to my
knowledge) and our species currently only resides on planet Earth, so any
weapon would be ballistic in nature, to strike targets on Earth's surface. A
reactionless drive would be ill-suited for ballistic propulsion because it
doesn't give enough thrust. If it was launched from the ground like an ICBM on
a suborbital trajectory, it wouldn't be able to escape Earth's gravity, it
would just sit on the launch pad. If it was placed into orbit using a rocket
as a first stage, and then activated later, it would take a while to deorbit
rather gently. The vehicle's velocity would slow down due to air resistance,
and its kinetic energy would not be usable as a mass destructive weapon. This
is why large explosions are used as weapons of mass destruction, and not
kinetic energy alone. Kinetic energy is simply used for timely delivery of the
explosive device from a great distance away.

Now, for interstellar warfare, a reactionless drive could be useful if you
were extremely angry at another planet in another star system located many
light-years away. The large distance between the aggressor and the victim
allows the kinetic vehicle a lot of time to accumulate velocity. However the
steering of such a kinetic weapon must be very precise in order to hit the
target planet, so the vehicle must have the means to estimate its current
location/speed/direction, compute the orbits of itself and its target, and
apply the necessary course corrections in order to hit that target. It is
possible that a reactionless drive might provide vectored thrust, but if it
does not, then attitude adjustment thrusters would be needed (either
reactionless or conventional.) Accurately steering a vehicle traveling near
the speed of light does not seem like an easy task. If the target was missed,
the vehicle would be traveling so quickly that it would escape the star system
on a hyperbolic escape orbit.

Such a weapon would be quite the undertaking and would be a large energy
expenditure for a civilization. It might be more worth it to focus that energy
into colonization and defense instead.

~~~
russell
>>> Rockets are certainly capable of accelerating a mass to a significant
fraction of the speed of light.

Well, yes and no. The speed of a rocket is limited by the specific impulse of
its engines. That means that hydrogen-oxygen rockets aren't going to go very
fast. Ion thrusters will go a lot faster, but take a long time to get up to
speed. If you want to go really fast you need something really exotic like
antimatter, but the technical challenges are quite daunting. Theoretically you
could use a flashlight, but the batteries would run out before you could get
anywhere.

The allure of a reactionless drive is that you aren't limited by the the
rocket equation. You may still need a big energy source, but your speed isnt
limited by how fast you can spit stuff out your backend.

It's fun reading to look up things like specific impulse, the rocket equation,
relativistic rockets, even project Orion.

IANARS.

~~~
mikeash
To be precise, the ultimate speed of a rocket is limited by the specific
impulse of the engines _and_ the mass fraction i.e. how much of the rocket is
fuel versus how much is not-fuel.

There's nothing that theoretically prevents a hydrogen-oxygen chemical rocket
from approaching the speed of light. But it would need an amount of fuel
roughly the size of the Sun to do it with any appreciable payload.

------
gus_massa
> _The result is a drive that exerts an intermittent net force in one
> direction. [...] Nor does it violate the principle of conservation of
> energy, because the system requires power for its operation._

Well, you actually can't do that. In special relativity when you change of
reference frame, the momentum and energy mixes. If you break the momentum
conservation in one reference frame, then you break the momentum conservation
and the energy conservation in almost all the other reference frames.

If you do the experiment on Earth and in that reference frame the energy is
conserved, then the astronauts from the ISS will see that the energy is not
conserved, if Elon go to to Mars he will see that the energy is not conserved,
even the people on the other side of the Earth will see that the energy is not
conserved.

If you put two of these devices in opposite orientations in the opposite sides
of a spinning carrousel (and assume that the angular velocity of the carrousel
is small enough to ignore it in the calculations) you will see that each of
the devices gain some energy and you can harvest it.

------
msandford
This seems much more plausible to me than the microwave thruster previously
reported all over the internet. I think it's a clever application of
relativity and motion. It feels crazy to say this, but it seems to be on a
solid theoretical footing.

~~~
dnautics
My thoughts exactly. Why _don 't_ they crowdfund this? For about $200k they
could probably stick a prototype on a nanosat and just hit go. With the right
tracking equipment the results should be pretty conclusive.

~~~
trishume
From my limited understanding, it seems that the current prototype requires a
ton of power (far more than you could fit in a nanosat) and produces a
miniscule amount of thrust (even in space with a nanosat it might not move
much).

------
joshuaheard
So, a change in the movement (flux) inside a capacitor is the key? A "flux
capacitor" you say?

------
vadman
"The problem is, crowd funding requires a significant investment of time,
which might be applied more productively to research."

So they can't arrange for a capable student to take care of that as part of a
work-study program? WTH. Perhaps I'm underestimating the amount of work
involved, but it's not like they need to have contributor tiers with silly
T-shirts.

~~~
api
Try to crowd fund this and you'll bring out hordes and hordes of Skeptic
Movement Skeptics who will scream "con man!" and "pseudoscience!" and do
everything they can to sabotage the campaign. Kickstarter would probably start
getting e-mail campaign letters to de-list his account for fraud, etc.

You see, he needs more money to try to boost the signal and further test the
effect. But since the effect is novel and controversial, attempting to raise
such money means he's a con man and invites comparisons to that e-Cat dude
from Bologna.

If I were him I would avoid publicity outside the scientific community simply
to avoid the character assassination. I'd work with interested other
scientists and publish in obscure journals until I could either find the flaw
my measurements or generate data so unambiguous that it overcomes the howling.

~~~
blacksmith_tb
Have other crowdfunded scientific projects had this problem? It's easier to
see why people might unleash a lot of criticism at projects that might receive
federal funding, but wouldn't the critics just... not back a crowdfunded test
of Woodward's work?

~~~
aperrien
Because, unfortunately, some people are just jerks, and will troll for the
luz.

------
arh68
I found the mention of Mach's Principle beyond intriguing. How have I not
heard of this?! I'm quite glad to ponder it [1]

    
    
        You are standing in a field looking at the stars. Your arms are resting
        freely at your side, and you see that the distant stars are not moving. Now
        start spinning. The stars are whirling around you and your arms are pulled
        away from your body. Why should your arms be pulled away when the stars are
        whirling?  Why should they be dangling freely when the stars don't move?
    

... _There have been other attempts to formulate a theory which is more fully
Machian, such as Brans–Dicke theory, but most physicists argue that none have
been fully successful. At an exit poll of experts, held in Tubingen in 1993,
when asked the question, 'Is general relativity perfectly Machian?', 3
respondents replied 'yes' and 22 replied 'no'. To the question, 'Is general
relativity with appropriate boundary conditions of closure of some kind very
Machian?' the result was 14 'yes' and 7 'no'._

[1]
[https://en.wikipedia.org/wiki/Mach%27s_principle](https://en.wikipedia.org/wiki/Mach%27s_principle)

------
matt_kantor
This article acts surprised about the possibility of changing an object's mass
by varying its energy, but I thought that was common knowledge among
relativists, as per [the classic "a compressed spring weighs more than a
relaxed spring" meme][1].

[1]:
[https://news.ycombinator.com/item?id=4196182](https://news.ycombinator.com/item?id=4196182)

------
mrfusion
I wonder if you could rotate the capacitor about a central point instead of
vibrating it?

~~~
ajuc
With magnetic bearings in vacuum and superconductor for the coil the only
energy loses would be the ones that this theory predicts due to mass
fluctuations I think?

So either it does nothing and stays where it is, or it converts energy into
movement at 100% efficiency?

~~~
api
Electric motors can be ~90% efficient, or even higher for really well
engineered ones, so very high efficiencies in converting electricity into
movement are common. Electricity is basically movement already -- of electrons
-- and is usually generated by spinning conductors and magnets around.

It wouldn't be 100% since some energy would be lost due to internal friction
and the need to actively cool the thing to maintain superconductivity (and
pump away heat generated by friction). You'd also lose energy in the
electronics in generating the oscillating signals, switching, power
conversion, etc., and in EMF losses. If it really does work I could imagine it
approaching the efficiency of a good motor, just one that creates directional
force in a vacuum by pushing against... umm... something. That'd be a question
for the theoreticians. :)

------
zvrba
Um. From what I remember of having learned about capacitors in a basic physics
course a long time ago, the net charge of the capacitor is always the same.
When voltage is applied to a capacitor, it generates an electric field between
the plates, which causes charge separation. The charge is already there, its
source is the dielectric between the capacitor plates.

So charging the capacitor may make one plate slightly lighter, the other
slightly heavier, but its overall mass is the same. Is it this mass change
he's trying to use?

~~~
mnw21cam
It isn't the charge on the plates that alters the mass - it is the stored
energy.

------
sopooneo
Someone who understands the _notion_ here, please tell me: would this violate
conservation of momentum or not?

~~~
ars
It does not change momentum or speed. But rather allows you to shift your
location. You do not wind up with any net velocity, or momentum.

~~~
sopooneo
Isn't it meant to help a spacecraft accelerate? And if that happens, doesn't
that mean that its mass has accelerate? And thus its momentum has increased?

~~~
ars
No. It just makes it move, but in between machine cycles (or if you turn it
off) the speed of the spacecraft is zero.

It requires no energy or momentum to just change position. Except it's
impossible to do in space, but this machine makes it possible (supposedly).

~~~
sopooneo
Very helpful. Thank you. But then why were they trying to demonstrate efficacy
by measuring torque, which I assume is just a proxy for force?

~~~
ars
I don't know. It should only develop cyclical force (back and forth - but
pushing against nothing).

I'm not 100% sure this thing actually is real, I'm just going by the
description in the wired magazine, plus reconciling it with the statement that
it doesn't violate Newton's laws.

------
MaysonL
I found it really noteworthy that a science fiction enthusiast, writing about
a "reactionless drive", would fail to mention the Dean Drive.

[http://en.wikipedia.org/wiki/Dean_drive](http://en.wikipedia.org/wiki/Dean_drive)

------
waterlesscloud
I want to go to physics grad school just so I can have a lab full of equipment
like that, with a lot of it stuff I machined myself.

~~~
pm90
Just join your local hackerspace instead, and you will still do all those cool
things, and more!

If you're in Austin:
[http://atxhs.org/wiki/Main_Page](http://atxhs.org/wiki/Main_Page)

~~~
TeMPOraL
It's late for me as I just finished my CS studies, but I realized recently
that the university is nothing but a more formalized Hackerspace with much,
much more expensive equipment. I'm thinking about re-enrolling, for biotech
this time, to get access to the lab.

------
brador
Second picture, anyone know what brand those keyboards are?

------
dang
Can someone please suggest an accurate, neutral title?

~~~
rudolf0
"The quest for a reactionless space drive"? That's the article's URL slug,
though not its title.

~~~
dang
Thanks! Title changed from "Strange thrust: the unproven science that could
propel our children into space".

~~~
TeMPOraL
Dang, I see you consistently active in many a thread, always telling what was
the original title when changing it, and asking for suggestions when you're
not sure. Thank you very much for that. It feels much better when the reason
for title change is explained and open for discussion. I like how HN is
improving itself recently.

~~~
dang
Thanks for saying so! It's good to hear.

------
jmount
Jeeze, really HackerNews/BoingBoong news are not good science sources. This
"reaction-less" drive is simple variation of the "Dean drive" (another "space
thruster" that only works if it is on a kitchen floor so that it can do
standard work and exploit the different scales of static and slipping
friction). I thought this was at least going to be the "microwave thruster"
that works in cheap partial vacuum (but not in actual deep vacuum). Not even
new bad ideas.

~~~
dang
It sounds like you know something about this topic. I don't, and I'm sure that
many other HN users don't either. Your comment would be better, I think, if
you assumed that people here are curious to learn and shared your knowledge in
a way that was easier to absorb. If bad ideas are circulating, offer better
ideas and explain why they are better. That strategy may not work everywhere,
but at least some of the time it does work here.

~~~
jmount
I guess I would say if you are truly curious about physics read about
conservation of momentum, Noether's theorem, and things like that. You get
really neat things like: if you assume general relativity is position
invariant then you can prove it has conservation of momentum (i.e. you don't
have to directly assume conservation of momentum!).

~~~
scott_s
I think what Dan was trying to nudge you towards was sharing some of your
knowledge with us, and starting some good discussion on those topics.

------
jules
So many pseudoscience articles today! We got one about solving NP complete
problems in polynomial time with a new kind of "brain-like" computer, and now
there's one about violating conservation of momentum. Next up: Peano
arithmetic is inconsistent & telepathy proven to work based on quantum
mechanics.

~~~
api
What exactly makes this pseudoscience? Is it pseudoscientific to investigate
unlikely or speculative possibilities?

They have presented evidence and a proposed mechanism, have fully published
the details of their work, and have invited others to attempt to replicate it
or to show where they're wrong. Where's the "pseudo"? It's also important to
note that in experimental physics it's more than enough to show an effect that
can be replicated. Their currently proposed theoretical explanation could be
wrong, but that wouldn't matter.

~~~
jules
They have an experimental setup that spits out some data. That data goes
against the theory of general relativity. Extraordinary claims require
extraordinary evidence.

The article also sets off various other pseudoscience alarm bells, such as the
fact that their paper is published in a philosophy journal, and the guy having
a history degree instead of a physics degree. But that goes against the naive
rebellious spirit of HN that dictates that anybody can overthrow fundamental
physics with an experimental setup in his basement, so downvote away!

~~~
mikeash
Going against established theory has nothing to do with "pseudoscience".
Pseudoscience is how you treat it. If you say, this is the next best thing,
all my doubters are idiots, and invest now! Then that is pseudoscience. But if
you just go, "hmm, that's funny" and keep investigating what's going on,
that's just plain science.

The article is very much written in the second form, at least as far as I can
tell.

~~~
ikeboy
"The most exciting phrase to hear in science, the one that heralds new
discoveries, is not Eureka! (I found it!) but rather, 'hmm... that's
funny...'"

[http://www.wisdomquotes.com/quote/isaac-
asimov-7.html](http://www.wisdomquotes.com/quote/isaac-asimov-7.html)

~~~
mikeash
I was attempting to reference that quote! But I couldn't find it (because I
thought it was from Einstein) so I didn't say so explicitly.

