
We need a better way to get to space - vishaldpatel
https://theconversation.com/its-not-rocket-science-we-need-a-better-way-to-get-to-space-45751
======
lmm
Much as I love to cheer for British engineering, I don't understand the logic
here. A rocket would require an expensive inspection before reuse but a
spaceplane wouldn't? Why?

Also not one SABRE engine has even been built yet, whereas SpaceX has got very
close to landing their rockets.

~~~
dredmorbius
SpaceX _have_ landed their rockets.

Just not ... in one piece.

~~~
charlesdenault
They've landed their rockets in one piece, which proceeded to tip over and
explode. An important distinction.

~~~
dredmorbius
A most excellent and nuanced distinction, sir! Capital!

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rm_-rf_slash
I'm no rocket scientist but I could imagine rockets having a place in regular
space travel. Lets assume that we can harness solar power efficiently and
safely store the extra energy in hydrogen and oxygen gas. Then let's say that
we could construct sturdy and modular components that can be disassembled and
re-assembled at some kind of orbital station, so that the boosters that take
people into orbit for whatever reason could be rebuilt in orbit to carry a
load of asteroid-mined metals back to the surface.

Again, I don't know any of the mechanics or physics, but if energy was
abundant and parts could be reused, would rockets really be all that bad?

~~~
7952
Sea Dragon [1] is slightly similar to that.

Fuel is a small part of the cost of a rocket, most of the cost is in the
engines and structures. Cheap production of hydrogen or oxygen is unlikely to
make things much cheaper.

Also, any mass left over at engine cut-off requires a large quantity of fuel
at lift-off and possibly necessitating a larger more expensive rocket. This
would make re-purposing of boosters in orbit less likely.

[1]
[https://en.wikipedia.org/wiki/Sea_Dragon_(rocket)](https://en.wikipedia.org/wiki/Sea_Dragon_\(rocket\))

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drewg123
I was hoping the article would talk about space elevators, and not space
planes. I'm eagerly awaiting materials science and geo-politics to mature
enough to allow the construction of space elevators.

[https://en.wikipedia.org/wiki/Space_elevator](https://en.wikipedia.org/wiki/Space_elevator)

~~~
jcfrei
I don't really see the benefits of space elevators, to be honest. At an
altitude of 100km the gravity is still virtually the same. And you still need
a huge amount of fuel in order to put your rocket/plane into orbit. Unless you
build an elevator with a height of 42'164km (geostationary orbit) - but that
seems unrealistic to me.

~~~
ZenoArrow
> "I don't really see the benefits of space elevators, to be honest. At an
> altitude of 100km the gravity is still virtually the same."

You would have made the first 100km of the journey more fuel efficient, is
that not a good enough reason?

~~~
jcfrei
I think it's just prohibitively expensive at the moment. 100km (I think it
would have to be a lot more anyway) is not much in terms of space exploration.
And even then you will always use the majority of your fuel for acceleration
towards and deceleration at your destination (however fuel needs for
deceleration might be much lower if you can do some sort of atmospheric
braking).

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7952
This thread [1] gives a good explanation of why Skylon should be treated with
scepticism.

[1]
[https://m.reddit.com/r/engineering/comments/2wstn6/i_am_very...](https://m.reddit.com/r/engineering/comments/2wstn6/i_am_very_interested_in_reaction_engines_and/)

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blisterpeanuts
It's a slick looking video, but what about reentry? It's not that hard to get
a ship up there (the X-15 was flying to the edge of space 50 years ago), and
launching like a jet plane obviously has many advantages over rockets, but
when it comes back down it's going to hit the atmosphere at a pretty high
velocity, unless it's carrying enough fuel to gradually lower itself back into
airspace where the jets can kick in. The craft in the video does not appear to
have VTOL capability.

But, if they can solve such problems, great. I'm thinking that eventually
we'll have some kind of electrical or hybrid mass driver (catapult) system for
getting non-human cargo into low orbit[1], much cheaper (and quieter) and
obviously could accomplish many launches a day for one-way missions.

You could get a large space station or interplanetary craft up there rather
affordably using this approach. Specialized reentry vehicles as well. Launch
the parts cheaply, robots assemble the parts in orbit, then launch the humans
expensively.

1\.
[https://en.wikipedia.org/wiki/Mass_driver](https://en.wikipedia.org/wiki/Mass_driver)

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Amorymeltzer
Space planes should absolutely be part of our strategy, but their
effectiveness diminishes once you get past LEO. An effective program would
have different vehicles for different purposes, using the right tool for each
job.

~~~
nickff
Taking mass to low earth orbit (LEO) is the gating item to increased space
travel and exploration; Skylon, SpaceX, Blue Origin, and Orbital Sciences are
all focused on reducing this cost. It is quite well understood that outside of
plans like Mars Direct and Semi-direct, interplanetary and interstellar travel
will require other technologies such as novel electric and nuclear drives, but
we are simply not at a point where that is an issue yet.[1][2]

[1]
[https://en.wikipedia.org/wiki/Ion_thruster](https://en.wikipedia.org/wiki/Ion_thruster)

[2]
[https://en.wikipedia.org/wiki/Nuclear_thermal_rocket](https://en.wikipedia.org/wiki/Nuclear_thermal_rocket)

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rikkus
20 years ago, I remember dreaming up a train pulling a cable with a glider at
the far end. I'm sure there are many technical issues with this approach,
possibly including the cable needing to be incredibly strong, light and
flexible. Please tell me it would work, though, as I still enjoy the mental
image.

~~~
nickff
Reaching orbit is mostly an issue of velocity, not altitude. This is why
balloons can get very high, above of almost all earth's atmosphere, while
being far from orbit. Rockets spend most of their ascent traveling nearly
horizontal to the ground (they only go straight up at the beginning to get out
of the densest part of the atmosphere).

~~~
rthomas6
What about geostationary orbit wrt balloons? Do the balloons slow down
horizontally a lot during the ascent? If not, what if we floated a rocket up
most of the way and let the rocket do the rest?

~~~
david-given
You've just described a ballocket. You launch a rocket from a very high
altitude balloon.

You gain nothing from the height, because you still need to spend ~10km/s
getting up to orbital velocity, but you don't have to push your way through
the thick lower atmosphere any more. Rockets don't work very well in
atmosphere, so you do get fuel savings due to more efficient engines.

I don't know if this has ever been tried for real.

~~~
T-A
Rockoon?
[https://en.wikipedia.org/wiki/Rockoon](https://en.wikipedia.org/wiki/Rockoon)
I particularly like the steampunk vibe of
[https://en.wikipedia.org/wiki/JP_Aerospace#Airship_to_Orbit_...](https://en.wikipedia.org/wiki/JP_Aerospace#Airship_to_Orbit_project)

~~~
david-given
Er. * cough * Yes, rockoon, not ballocket.

In my defence I (a) am coming down with a horrible cold, and (b) read The
Register...

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skizm
So is infertility in astronauts still a problem? I could be totally wrong, but
I was under the impression we haven't solved the problem of increased
radiation negatively affecting fertility in both male and female astronauts.

~~~
simonh
I'd have thought sperm/egg freezing would do the trick.

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Mvandenbergh
For all that effort to reduce oxidiser mass by using atmospheric oxygen, it's
still 80% propellant by mass. Saturn V was 85%.

Still impressive if they can make it work, since of course Saturn V wasn't
reusable.

~~~
avmich
So, with Saturn-5 only 15% was dry mass - and with Skylon 20%? That's 33%
increase. Moreover, Saturn-5 was staged - and Skylon is single-stage, and have
single stage to orbit with 20% dry mass looks somewhat like a miracle.

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anon8764
www.et3.com gradually leading up to the top of everest, jettisoning the
capsule (6,500 km/h (4,000 mph)) to break out of the atmosphere.

I have not done the math, physics, etc on this, but it's an interesting idea
worth exploring.

But that said, do we really belong in space when we cannot care for our own?
Wouldn't that be akin to giving sugar to ants? only multiplying suffering and
cruelty exponentially in space? Perhaps a refactoring of our culture and our
methods of using/allocating/expending resources should be our first priority.

~~~
iamcurious
Interesting, let's say it should be our first priority, how does that
translate into action? Please remember that mobilizing large amounts of people
towards a goal is hard problem, specially when the goal involves copious
amounts of research and experiment.

~~~
anon8764
I personally believe people do not deserve to go to space yet.

They haven't mastered the ability to house, clothe, and feed the human family
yet, despite having the technical ability to do so. As a result of this, you
see the derivatives that exist today. Walk among Miami at night and you see
homeless crackheads muttering to themselves while sipping on beer. The
conditions that cause a person to do this would be probabilistically lower
with a society that cares about one another more [designed-in] instead of
fighting amongst each-other for paper slips.

If we absolutely need to go to space, we require research to determine the
amount of materials needed to build this track length, and the renewability of
those materials in reference to the earth. If this request for the materials
meets a certain threshold, it will be dispensed, otherwise, the remaining
materials can be reserved for further research to create synthetic
alternatives. It helps to have a global database of known resources and their
reserves, in fact, it might be a crucial requirement.

Imagine culling redis for this information, it sends a request to the global
cybernetic hub, and it permits or denies the request, along with the terminal
node you requested it to be sent to...

example: I request 13 Ounces of Gold (AU) at terminal #324-214-495-2341 to
perform an experiment. (Since gold is currently in enough abundance for my
request it is sent to my terminal as soon as technically possible, and any of
the resource I do not use or can scrap back to the global hub, is done so)

~~~
iamcurious
So all resources are to be distributed from a central organization. Pray, who
will be decide this? How will disputes will be solved when, inevitably, an
armed group decides to use resources some other way?

Also, the whole point of leaving earth is leaving scarcity. There are
meteorites with gold, we can and we should mine them as we see fit.

~~~
anon8764
By creating abundance, it lessens the need and purpose for armies to take
resources from others. There are no armies I am aware of that invade and
conquer for Oranges, but they do for Oil.

To complete your second statement, why do you believe we should mine them for
gold when we cannot efficiently manage them here on Earth to begin with?

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aggieben
Giant railguns. That is all.

~~~
iwwr
Light-gas guns may be a good contender while railguns are sorted out.
[https://en.wikipedia.org/wiki/Light-
gas_gun](https://en.wikipedia.org/wiki/Light-gas_gun)

~~~
chris_va
Surprisingly, I actually did a fair bit of research into this field.

Both rail guns and light gas guns cap out at around 6km/s, and you really want
8km/s (more actually, for hypersonic drag loss) for this to be economical.
Otherwise you need to launch a large enough rocket to make up the 2km/s
difference, and you stuck solving the rocket equation again. Except you've
subjected your rocket to 1000g, and the odds of it being reusable are really
small.

For rail guns, the plasma discharge on the rails limits your speed. Around
6km/s.

For light gas guns, the working temperature of the gas cannot exceed the
melting point of the barrel (or get close), otherwise tungsten/steel will get
into the working gas and slow down the speed of sound. With hydrogen+tungsten,
also around 6km/s.

There is a better solution, though :).

~~~
rakoo
> and you stuck solving the rocket equation again

Yes, but only for 2km/s, so there's that. Also this system can be used on
other bodies such as Mars and the Moon.

But yeah, I'm more worried about the 1000g than anything.

~~~
chris_va
2km/s means you are limited to about 20% payload. 20% is 10x better than a
normal rocket, but there are actually easier ways to get 20%.

The beamed power method gets about 20%, and works for humans (no g load).
Escape Dynamics is trying it:
[http://escapedynamics.com/edispacelaunch/](http://escapedynamics.com/edispacelaunch/).

The difficulty here is more technical/scientific than engineering.
Synchronizing microwave beams is hard, and if you don't you get destructive
interference. I don't know if they have solved that problem yet (there have
been a few proposed solutions, we'll see if any work).

Edit: Yes, rail would work great on the moon/mars. Actually there was a movie
(Moon, with Sam Rockwell) where fuel is harvested on the moon and shot into
orbit. Fun, crazy movie.

