New Mars Forums

Official discussion forum of The Mars Society and MarsNews.com

You are not logged in.

Announcement

Announcement: We've recently made changes to our user database and have removed inactive and spam users. If you can not login, please re-register.

#1 2018-04-12 04:16:16

louis
Member
From: UK
Registered: 2008-03-24
Posts: 3,486

Reaction Engines secure funding.

Reaction Engines are making good progress:


http://www.bbc.co.uk/news/science-environment-43732035


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

Offline

#2 2018-04-12 08:05:24

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 3,029
Website

Re: Reaction Engines secure funding.

Well,  it looks like they solved the multiplicity of problems with the cooler.  Those were the bugaboo with liquid air cycle engines for the last 6 decades.  The problem for Reaction Engines will be getting their nifty little toy taken away from them by the big-monied giants whose attention they have finally captured.

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

Offline

#3 2018-04-12 10:49:19

Void
Member
Registered: 2011-12-29
Posts: 2,256

Re: Reaction Engines secure funding.

This topic and the members involved, cause me to make an exception to my intended behaviors on this board.  So, I will post.  Lucky you. smile I am wondering if that method will eventually be adapted to BFR's (Or similar) 1st stage only.

Technically breathing atmosphere on the way up is Insitu, even though the time span is short relative to procuring propulsive resources on Mars.

I will not blab much about harvesting gas from the Earth's Exosphere, or from the Moon, but those are also possible "Staging" events in the future.

The whole thing begins to make me wonder if Elon Musk's numbers for the transfer of people to Mars could be very conservative.  What if in the further future, a trip to Mars would cost only $50,000.00 or even less?

Last edited by Void (2018-04-12 10:57:01)

Offline

#4 2018-04-13 08:01:23

elderflower
Member
Registered: 2016-06-19
Posts: 820

Re: Reaction Engines secure funding.

Discounted seats for last minute bookings! Extra for hold baggage! Take your own sandwiches and water. Book your return at the same time or expect murderous gouging from a monopoly supplier if you don't want to stay.

Offline

#5 2018-04-13 13:03:41

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 3,029
Website

Re: Reaction Engines secure funding.

SABRE is really a liquid air rocket.  The problem is how much air is scooped up in flight is not constant with altitude.  That limits the rocket engine massflow (and thrust!!) at high altitudes in the thin air.  That's a similar limitation to all the other airbreathing engines,  something not shared by self-contained rockets. 

Thrust is crudely proportional to the atmospheric pressure.  Go look in any standard atmosphere table at the ratio of local altitude pressure to sea level pressure,  and roughly,  that's your sea level thrust multiplier.

There's more to the problem than just Isp.  If you don't have high frontal thrust density,  you don't climb!  Period.  This effect is precisely why airplanes powered by airbreathing engines have service ceilings.  This liquid air cycle engine is no magic bullet for cheap and easy space access. 

And the Skylon airframe these engines are supposed to power is insane.  The tip-mounted engines will shed shock waves during reentry that will cut the wings right off the vehicle. 

They plan to fly as an airbreather up into the thin air at only Mach 5 or so,  somewhere around 80-100,000 feet maybe,  and go steeply upward from there on rocket power alone.  It'll survive an ascent like that.  It will not survive peak reentry deceleration and heating at about 150-250,000 feet and Mach 12-15-ish. 

The bugaboo is called shock impingement heating,  and it is quite real. 

GW

Last edited by GW Johnson (2018-04-13 13:09:30)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

Offline

#6 2018-04-13 16:31:24

louis
Member
From: UK
Registered: 2008-03-24
Posts: 3,486

Re: Reaction Engines secure funding.

I must admit I feel it is a bit of a diversion...

Longer term, ground laser (or microwave beam) powered launch seems to me more promising as an alternative to chemical rockets. Pollution from chemical rockets is, I would suggest, going to become a big issue if Space X's plans are realised. Currently with just a few rocket launches each week around the globe it's manageable but not if you have hundreds or thousands per week. Rockets spew pollutants all over the place.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

Offline

#7 2018-04-13 20:43:26

Oldfart1939
Member
Registered: 2016-11-26
Posts: 1,389

Re: Reaction Engines secure funding.

Hmmm? "Rockets spew pollutants all over the place." When we burn natural gas in electric generation plants, we get exactly the same combustion products as a  MethylOx powered rocket: CO2 and H2O. Not really that polluting, and more like plant fertilizer.

Offline

#8 2018-04-14 03:44:18

elderflower
Member
Registered: 2016-06-19
Posts: 820

Re: Reaction Engines secure funding.

Skylon is designed to burn Hydrogen and air at low level and hydrogen and LOX in space mode. Product is water with, perhaps, a bit of excess hydrogen if they run it rich. No direct pollution, but air separation plants and reformers create direct and indirect pollution when they are in operation. Neither LOX nor free Hydrogen occur naturally on Earth.
I do hope Reaction Engines have a solution to the shock impingement issue!

Offline

#9 2018-04-14 19:56:19

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 12,010

Offline

Board footer

Powered by FluxBB