To know the kind of engine you need, you need to know the vehicle it will be used for.

To know the kind of vehicle you need, you need to know where it is going and what the vehicle is used for.

To know where you are going and what you are doing, you have to have a long-term plan.

Is anyone doing this?

NASA is not - not officially.

China is - officially.

* * *

Chinese Engines

YF-77 (165,000 lbf)
http://aviationweek.com/awin/chinese...xceed-saturn-v


Chinese Vehicles

Long-March 11 (140,000 lb LEO)
http://www.americaspace.com/2012/07/...g-new-rockets/

Chinese Missions

Mars
http://en.people.cn/200705/22/eng20070522_376754.html

Solar Power Satellite
http://news.xinhuanet.com/english/20..._134109115.htm

* * *
A 140,000 lb payload to orbit, built with a common core and two outboard stages - all to the same design. Five Y-77 engines on each.

So, three modules each the same size and weight is about 1/2 the size of a Space Shuttle External Tank, with FIVE Y-77 engines at the base of each.

Each module;

316 tonnes module weight

36 tonnes structure weight Structure
43 tonnes LH2
237 tonnes LOX
77 Y-77 Engine Thrust
5 Number of Engines
1.218 Gees at lift off.

So, theres a core, and two outboard tanks, equipped with cross feeding, drain the two outboard tanks first and blast off with 15 Y-77 engines. When the two outboard tanks are drained they are dropped and fly back to the launch centre after boosting the system to 2.2 km/sec.

The central core adds another 5.8 km/sec to attain orbit with 63.6 tonnes payload. The central core re-enters, and returns to the launch centre.

* * *

Reaching for 400,000 lbs.

Expanding to 7 common core boosters with five Y-77 engines - raises the weight higher.

A seven element launcher puts up 182.0 tonnes payload (400,000 lbs) with four elements dropping off and flying back to the launch centre after adding 1.5 km/sec. The three element system continues as the second stage. The two elements dropping off after taking the vehicle up to 4.3 km/sec. Then finally the core element takes 182 metric tons to LEO. All fly back to be reused.

* * *

What to do when you get to orbit -

Interplanetary Stages - Nuclear thermal stage -

One interesting detail is the development of ceramic coated pellets of uranium that contain liquid uranium under supreme heating achieving 1600 sec Isp (15.68 km/sec Ve) using liquid hydrogen. This is an old idea, going back to the 1960s;

https://books.google.co.nz/books?id=...XGA9cQ6AEIJTAA

A 4000 MW thermal nuclear rocket the size of NERVA, operating at this level, produces 52.0 metric tons of thrust. The advantage of this system 182 metric ton payload can deliver a lot more across the solar system than chemical rockets!

https://www.lanl.gov/science/NSS/iss...ory4full.shtml

Nuclear Electric Stage

The nuclear thermal source is also used as a power supply using a closed Brayton cycle process. This produces 2000 MW electrical, from a 4000 MW thermal source which when used in an advanced ion engine that produces 54 km/sec exhaust speed (5500 sec Isp) produces 7.5 tonnes of thrust providing even greater payload fractions to Mars and beyond, and mass only 1.5 tonnes.

On board Nuclear Electric & Nuclear Electric on Mars

A nuclear thermal source will be used as a power supply to power the ship, the same way the nuclear power plant on a nuclear sub is used. The nuclear thermal source will be used as a power supply after landing. To power a lunar or mars or other planetary city. Including industrial processes that produce chemical fuels on Mars for boosters.

http://emits.sso.esa.int/emits-doc/E...33-SoW-RD1.pdf

For all these reasons, anyone serous about deep space manned travel will develop nuclear rocketry.

The PR angle

The technology is different enough from existing power plant designs, that they can be incorporated in advanced high temperature reactors on Earth, and the high profile nature of the successful missions they enable, are sufficient to promote their high technology, high reliability and high safety. A definite coup. Something the Chinese would exploit mid 21st century to sell compact high efficiency flexible power plants to cities and nations around the world struggling in a post oil future.

https://www.gen-4.org/gif/jcms/c_9362/vhtr

The radiation angle

What about radiation? Well, Cosmic Background Radiation and Solar radiation outside vanAllen belts of Earth, are definite safety hazards as well. The shielding required of a nuclear source could also shield astronauts aboard ship. A shadow shield has long been promoted as a 'safe haven' or 'storm shelter' or even a 'sun shield' for manned interplanetary missions. Another is to use powerful electro magnet and surplus electrical power to make a mini-magnetic shield around the ship.

https://home.cern/about/updates/2015...eld-astronauts

* * *

It takes 3.6 km/sec to exit LEO and head for Mars along a Hohmann Transfer Orbit. So, propellant fractions are;

Chemical
u = 1 - 1/exp(3.6/4.3) = 0.557 -- 39,930 lbs useful of 140,000 lbs, 114,100 lbs useful of 400,000 lbs

Nuclear Thermal
u = 1 - 1/exp(3.6/15.68) = 0.200 -- 98,970 lbs useful of 140,000 lbs, 282,770 lbs useful of 400,000 lbs

Nuclear Electric
u = 1 - 1/exp(3.6/54) = 0.063 -- 118.190 lbs useful of 140,000 lbs, 337,700 lbs useful of 400,000 lbs


A nuclear thermal rocket powered stage delivers 2.48x what a chemical stage delivers.
A nuclear electric rocket powered stage delivers 2.96x what a chemical stage delivers.

Now, a nuclear electric power source has a lot of other uses as well! So, a nuclear electric source, built around a nuclear thermal rocket, is a reasonable add-on to a nuclear thermal rocket programme.

If you're going to send large numbers of payloads across the solar system, you can do it more cheaply with the right engines, and nuclear rockets are the right engines.

* * *

Now this uses 1950s era technologies, updated slightly for today. Something the Chinese would feel comfortable doing as part of an integrated programme.

https://www.google.co.nz/url?sa=t&rc...e4ZL10FXWssogw

So, despite the small size of the Chinese Space Budget about 1/10th the size of NASA, in combination with support from the Chinese nuclear weapons and power programmes, a credible effort is being sustained along the lines described here.